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_ COMPACT DISC-INTERACTIVE _ ADESIGNER’S OVERVIEW |

Edited by Philips International - J.M. Preston Kluwer

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Compact Disc-Interactive: A Designer’s Overview

Compact Disc-Interactive A Designer’s Overview

Edited by J.M. Preston of Philips International in Eindhoven

Foreword by G.A.J. Bastiaens, Director Consumer Elec- tronics, Interactive Media Systems, Philips International BV and G. Stulberg, Chairman & Chief Executive Officer, American Interactive Media Inc.

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Kluwer Technical Books Deventer - Antwerpen

Distribution:

Kluwer Technical Books P.O. Box 23

7400 GA Deventer

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ISBN 90 201 21219

First edition, December 1987 Second edition, March 1988 Second printing, November 1988

All rights reserved. No part of this book shall be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without written permission from the publisher. No patent liability is assumed with respect to the use of the information contained herein. While every precaution has been taken in the preparation of this book, the publisher and the author assume no responsibility for errors or omissions. Neither is any liability assumed for damages resulting from the use of the information contained herein.

FOREWORD

Compact Disc is without doubt one of the most successful products in the history of Consumer Electronics. Of the many reasons for this success the following three are the most important:

* The specific properties of the CD system e.g. compact in size, easy to handle digital encoding, perfect sound, fast access, massive storage capacity, as well as its ability to be used in many different environ- mental conditions.

¢ A comprehensive and attractive disc software catalogue.

The same is true for the newly introduced CD-Video where high quality video is combined with CD sound. A third successful product in the optical family is the CD-ROM, mainly used as a computer peripheral for fast retrieval of text and data. The combination of high quality audio with video, graphics, text and data, all interleaved together and offering fast information retrieval under user control, has created a new and fas- cinating product, called CD-Jnteractive or CD-I.

CD-I offers a degree of flexibility in the presentation of information never before possible in consumer products, bringing a new dimension to the ways in which information will be published, distributed and used. It combines the power of a computer system for fast access to in- formation, with the excitement of attractive multimedia software for entertainment, education and information in such a way that the con- sumer is unaware that there is a computer involved. He or she just enjoys the application on the disc.

It is self evident that music is an interesting source of software for CD-I, combining music with the display of high quality pictures, or even motion pictures, together with text and data. We believe that this will create many enjoyable applications. Adding sophisticated new video and audio enhancements to adventure games or games of skill will create an interesting new range of entertainment software.

The need to improve the quality of education both in the home and school environment will be one of the most universal priorities in society during the next decade and there CD-I, as a truly multi-media system, can offer the type of breakthrough required. CD-I will help the user keep up to date with the latest developments in his or her area of activity, setting the pace according to the user’s level of knowledge. Reviewing or re-checking of

the source material by virtue of CD-I’s fast access capability becomes much easier and more exciting than browsing through a book. Even existing publications, suchas, for example, an encyclopedia, will become a completely new product realizing the full flexibility and potential offered by CD-I.

As we consider CD-I principally as a software driven mass consumer multi-media system, its success depends entirely on the attractiveness and variety of the software catalogue. This software catalogue will contain video enhanced music, games, sports, reference books, self help, children programs, all kind of educational material as well as tourist and travel information.

Alongside the very interesting consumer and educational market CD-I will create attractive possibilities for the institutional and professional area, typically in point of sales, point of information and training applications.

One of the critical factors of success for CD-I is the availibility of qualified authoring systems. For this, several possible authoring en- vironments are available, such as Microware, Microboards, Sun, and Optimage. Alongside these systems there are prototype CD-I players which will be available to form part of low cost authoring equipment.

Sony and Philips have now completed the CD-I technical specifications, known as the "Green Book Standard". The hardware and software industries are now actively involved with the preparation for the in- troduction of CD-I.

Many software companies are already preparing software for CD-I. Our own American Interactive Media Company (AIM) is preparing the software catalogue for the US market, together with many other software providers, while similar developments are also in progress in Europe (EIM) and Japan (JIM). We are convinced that other companies will become part of this fascinating development.

We firmly believe that this book will give an excellent introduction to the CD-I software creation environment, because "the software is the key to success".

G.A.J. Bastiaens G. Stulberg Director Consumer Electronics Chairman & Chief Executive Officer Interactive Media Systems American Interactive Media Inc.

PREFACE TO SECOND EDITION

This book is an introduction to CD-I. It has been written to provide an overview of the current state of development for those who want to know more about the topic - perhaps with an ambition to become CD-I publishers or to become CD-I designers.

It is not a designer’s guide. That is, it cannot be used as a vademecum while designing a CD-I disc. At the time of writing there is an insufficient body of experience to enable such a guide to be written - only two CD-I discs have been displayed to Licensees, one by Sony in June 1987 and one by Philips in December 1987. The book does, however, represent the cumulative experience of most of those already involved in CD-I.

It is likely that the book will go through many revisions as the body of experience grows and many of our expectations are either confirmed or denied. The long term success of CD-I is going to be determined by the foresight of the publisher and the ingenuity of the designer; so the more experience can be shared at this stage, the greater the effort that can go into original design work. The reader is therefore invited to write to the editor (c/o the publisher) with comments and criticisms so that subse- quent editions may be both more informative and more comprehensive.

This second edition has been edited by Dick Fletcher of New Media Projects in London. The substantial revisions to the first edition have been made possible in particular by the guidance and detailed comments of:

Richard Bruno of Optimage in Chicago

Peter Cook of Grolier Electronic Publishing in New York Peter Essink of Japan New Media Systems in Tokyo Nicholas Lewis of New Media Projects in London

Graham Sharpless of Home Interactive Systems in Eindhoven

J.M. Preston Philips International Eindhoven

1 March 1988

Table of Contents vii

TABLE OF CONTENTS

HOW TO USE THIS BOOK /

CHAPTER 1: INTRODUCTION 3

CD-I TRUE MULTI-MEDIA TECHNOLOGY 3 WHAT IS MULTI-MEDIA? 3

Why is Multi-media important? 3

Multi-media CD-ROM 4

CD-ROM XA 4

LaserVision 4

CD-I and Multi-media 5 BEYOND MULTI-MEDIA: HYPERMEDIA 5 INTERACTIVITY - THE ’I’ INCD-I 6

What is Interactivity? 6

How to use interactivity? 6

Interactivity : The Educator 7

Do Consumers Want Interactive Programs? 7

CHAPTER 2: THE BACKGROUND OF CD-I 9

THOSE CHILLY SATURDAYS 9 ELECTRONIC PUBLISHING 1/1

OPTICAL DISCS /2

COMPACT DISC (CD) /5

COMPACT DISC - DIGITAL AUDIO (CD-DA) /5 ANALOG AND DIGITAL 16 INTERNATIONAL STANDARDS 16 COMPACT DISC - INTERACTIVE (CD-I) 17 THE CD-I PLAYER 17

CD-I AUDIO /8

CD-I VIDEO /8

THE DESIGN PROCESS 19

CHAPTER 3 : WHAT CD-ICAN DO 2]

USING AN INTERACTIVE TELEVISON SET 2/ AN EXAMPLE : CD-IGOLF 22 AUDIO 23

Quality Levels and Capacity 23

viii CD-l: A Designer's Overview

Soundmaps 25 Specialist Use 26 Audio Control 26 VIDEO 26 National TV Broadcast Standards 26 Resolution 26 Safety Area 27 Compression 28 Coding Techniques 29 Image Planes 31 Motion 32 VISUAL EFFECTS 34 Single plane operations 34 Cuts 34 Sub-screens 35 Scrolling 35 Mosaic Effects 36 Fade 38 Two Plane Effects 38 Transparency 38 Chroma Key 38 Mattes 39 Transparent Pixels 39 Dissolves 40 Wipes 40 REAL-TIME INTERACTIVITY 41 Real-Time Data 41 Synchronization 4/ USER INTERFACES 42 Physical Interface 42 Interacting with the user 43 CONCLUSION 43

CHAPTER 4: THE DESIGN BRIEF 45

DEVELOPING THE DESIGN BRIEF 45 DEVELOPING THE IDEA MAP 52 TREATMENT 54 THE DESIGN TEAM 54

A Typical Design Team 55 BUDGET AND SCHEDULE 56

The Production Process 57 CONCLUSION 59

Table of Contents ix

CHAPTER 5 : DESIGNING FOR PRODUCTION 1 6/

DEVELOPING THE STORYBOARD 6/ THE CD-I AUTHORING ENVIRONMENT 61] The Designer’s Station 63 The Production Facility 63 Disc Building 64 Standard Data Formats 64 Scripting Subsystem 64 Audio Subsystem 65 Video Subsystem 65 The Presentation Editor 65 The Database Subsystem 65 Testing and Simulator Subsystem 66 BASIC PRINCIPLES 66 Tracks and Sectors 67 Disc Capacity 68 Data Transfer Channels 69 Data Transfer Channels: Audio Playback 70 Data Transfer Channels: Video Playback 7/ System RAM 72 Microprocessor 73 THE MECHANICS OF CD-I DESIGN 74 Interface Devices 74 Screen Design 74 Screen Effects 75 Controlling the Dataflow 77 Interleaving 77 Seek Time 79 Synchronization 80 Synchronizing to Audio 80 Synchronizing to Video 81 Timed Cues 8/ Interactive Design 8/ CONCLUSION 82

CHAPTER 6 : TYPICAL CD-I APPLICATIONS 83

THE GROLIER MULTI-MEDIA ENCYCLOPEDIA 85 Designing the Interactivity 85 Mode of use 85 Data Management 86 Screen Interface 86 Menus 86 Screen Effects 87

x CD-I: A Designer's Overview

Graphic Control Panel 87 Interactive Branches 87 Domain Seeks 88 HOT SHOT SPORTS 88 Photographic Database 89 The Animated Figure 92 Action Areas 93 Audio 94 COUNTRY HOUSE MURDERS 94 Surrogate Travel 94 Handling Disc Space 95 Icons 95 Audio 96 POP SHOWCASE 96 Partial Screen Updates 97 Disguising Disc Seeks 97 Singalong 98 Screen Proportion 98 INTERACTIVE UNDER FIVES 99 Shape Recognition 99 FRENCH PHRASEBOOK 100 Chroma-key Facility 102 Real-time Dramatizations 102 CONCLUSION 107

CHAPTER 7 : HOW CD-I WORKS 109

DISC STRUCTURE 109 Disc Organization 109 Disc Label 110 Path Table and Directories J/1 Files 112 CD-ISECTORS //2 CDI Sector Format 112 CD-I Audio Sectors 113 CD-I Video Sectors 114 DYUV Images 115 CLUT Images 1/5 RGB 5:5:5 Images 116 Run-Length Images 116 Program Related Data sectors 117 CD-I DECODER 117 CD-Drive/Player 118 Audio Processor 120 The Audio Processing Unit 121

Table of Contents xi

Video Processor 12] RGB Levels 125 Display Control Program (DCP) 126 The Hardware Cursor 128 Border Color 128 DMA Controller 129 Random Access Memory (RAM) 129 Non-volatile RAM (NV-RAM) 1/30 Clock/calendar 130 Pointing Device 130 Transfer Paths 130 Application Software 130 Audio Pathways 132 Playback from System Memory 1/32 Video Pathways 132 Image Store (RAM) 1/32 CD-RTOS 133 Organization 133 THE KERNEL 1/35 Configuration Status Descriptor 135 Start-up Procedure 135 File Protection 1/37 FILE MANAGERS 137 UCM Video 137 UCM Audio 139 UCM User Interface 139 Compact Disc File Manager (CDFM) 139 NV-RAM File Manager (NRF) 140 DRIVERS 140 SYNCHRONIZATION AND CONTROL 1/40 Play Control Structure /4/ Real-time Control Area 14] InVision 142

APPENDICES A: TECHNICAL SPECIFICATION SUMMARY 1/43

B: AGLOSSARY OF TERMS 1/45 C: CD-RTOS AND INVISION 20]

INDEX 237

HOW TO USE THIS BOOK

This guide has been designed to accommodate a variety of readers’ needs and interests. It is anticipated that some people will need to study in depth, while others will want only an introduction. Even those who will eventually study the entire guide may read selectively at first, to gain a solid background before coming to grips with the finer details.

The book grows more technical as it progresses. The seven chapters break down this way:

Chapter 1 explains the concepts of multi-media and interactivity.

Chapter 2 offers a general background to electronic publishing and optical disc technology. The CD-I player and disc are described, together with the principal audio-visual features of the system.

Chapter 3 looks at the audio-visual side of the technology in more detail, and explains what CD-I can do, and the design implications of its many features.

Chapter 4 looks critically at the kind of questions the potential designer must ask before undertaking a CD-I project and designing the brief.

Chapter 5 discusses the design process in some detail, and describes essential stages and production tasks.

Chapter 6 presents a range of hypothetical projects which might be among the first CD-I discs on the market: a multi-media encyclopedia, a pop music program, a language program, and several different game styles. Some of the various features and design considerations unique to CD-I are illustrated by specific examples within each application.

Chapter 7 discusses the technology in depth, from a computing perspective, and describes elements of the player and the technical composition of the disc itself.

While the book flows logically from Chapter 1 to Chapter 7, readers with different needs and interests may want to approach the guide itself interactively’.

Chapters 1 and 2 provide a general introduction and are appropriate for senior management and strategists.

How to use this book

1

2 CD-Il: A Designer's Overview

Itis likely that the potential CD-I designer or producer will read the whole book, but may wish to begin with the first two chapters for a conceptual introduction, and skip to Chapter 6 to look at how typical applications might work. Many may then prefer to think about the design process described in Chapters 4 and 5 before tackling the technical material.

What to look for © Chapter 1: multimedia and interactivity

Chapter 2: optical publishing panorama

Chapter 3: the media palette

Chapter 4: some pre-design questions

Chapter 5: design considerations

Chapter 6: some CD-I examples

Chapter 7: inside the technical system

Appendices: © Glossary ° CD-RTOS and InVision ° Index

Because this guide covers so much inter-related material - such as the description of a feature from both a design and a technical point of view - it contains aids to help readers cross-reference new ideas and concepts as they appear in different contexts. These include:

CHAPTER 1: INTRODUCTION

This chapter introduces the two basic concepts behind Compact Disc-Interactive (CD-1), the most recent development in the tradition of optical disc recording - multi-media and interactivity.

CD-I: TRUE MULTI-MEDIA TECHNOLOGY

Compact Disc-Interactive (CD-I) will be the first publishing medium to bring the world of multi-media to a broad general audience. It is essential for the CD-I publisher, designer and producer to understand this concept, and why CD-I is so much better suited to multi-media applications than other technology.

WHAT IS MULTI-MEDIA?

The term multi-media originated with the audio-visual industry, to describe a computer-controlled, multiple-projector slide show with a sound track. In computer terms, multi-media is viewed as a blending of media types: text, audio, visual, and computer data in one convenient delivery medium. Although CD-I is not the only combination of hardware and software capable of delivering multi-media information, it is the first to do so in a highly standardized form - and, for broad acceptance of a technological concept such as multi-media, system standards are a prerequisite. CD-I has been defined as a system standard, in contrast to CD-ROM which functions simply as a peripheral to a system. The CD-I specification defines how the information is stored on the CD-I optical disc, exemplifies how it is encoded in the recording studios, and defines how it is decoded in the player. A peripheral such as CD-ROM defines only how the information is stored on the disc, making international agreement on recorder and player standards impossible.

Why is Multi-media Important?

Information sources such as books, periodicals, film, television, radio, video, LPs, cassettes, and computer software, have evolved along various tracks and, in our minds, are viewed as separate and distinct media. But information need not be defined by the medium in which it is presented. The development of CD-I enable us for the first time to mix information from a variety of sources, using the medium most appropriate to the message - a short sequence of images called a video clip, computer animation, or a screen full of text, all supported by any combination of speech, music and sound effect as needed. CD-I combines the best

Chapter 1: Introduction 3

4 CD-l: A Designer's Overview

creative concepts from book design, film and video production, sound recording, and software design. This represents a new range of challenges for the designer, who must select the most effective combinations from the rich media palette of CD-I.

Multi-media CD-ROM

CD-I is an optical disc technology, the logical extension of both the Compact Disc and Interactive LaserVision. In 1985, CD-ROM (Compact Disc-Read Only Memory) was introduced as a mass storage peripheral for personal computers (PCs). Though developed primarily for text, it can store digital data of any kind, including sound and graphics. However, the multi-media potential of CD-ROM is defined by processing power, audio output, and the display capabilities of the computer that is controlling the CD-ROM drive. While most PCs can generate adequate audio and graphics output for computer applications, they were not designed to produce high quality audio or to display natural video images. CD-ROM is nevertheless well suited to dedicated solutions, where internationally agreed standards do not play a significant role.

CD-ROM XA

N.V. Philips, Sony Corporation and Microsoft recently together announced the joint development of an extended, multimedia format for CD-ROM, known as CD-ROM XA. The CD-ROM XA development is based on the following approach:

® Interleaved audio in ADPCM format, as defined in the CD-I format.

® Interleaved text/graphics, based on specified screen format for perso- nal computer displays.

CD-ROM XA will provide a variety of functions which are similar to those found in the CD-I format, but which will not be dependent on a specific software operating system or microprocessor. This new format will allow publishers to create discs which will be able to be played on any suitably equipped personal computer, as well as on the CD-I system. CD-ROM XA will also add a new dimension to the type of applications where CD technology can be applied, in both the professional as well as the consumer markets. It will also form the bridge linking CD-ROM with CD-Interactive.

Laser Vision

With the commercial introduction of LaserVision in the 1970s, many pioneers in the computer industry saw the opportunity to combine the audio-visual riches of videodisc with the processing power of the

personal computer. The result was interactive video (IV), a multi-media hybrid that uses the videodisc as a computer peripheral.

In interactive video, computer software stored on a floppy or hard disc generates text and graphics, and controls the access of sound and images from the videodisc - in response to actions of the person in front of the screen (who may be using a keyboard, mouse, touch-screen or other device). Interactive LaserVision has developed as a specialist’s technology, particularly effective for training and point-of-sales materials. Despite this success, it has not penetrated into the broader markets of education and the home to any significant degree, because of the high cost of the hardware, and a lack of standards for both hardware and software.

CD-I and Multi-media

Unlike the videodisc and CD-ROM, CD-I has been designed for multi-media consumer applications. Its technological premise is the complete integration of all media types. How CD-I achieves this, and the full range of CD-I multi-media capabilities are fully explained in the chapters that follow.

BEYOND MULTI-MEDIA: HYPER-MEDIA

The concept of hyper-media could have been invented to describe CD-I. Its origins lie in the notion of hyper-text, a term coined by computer guru Ted Nelson in 1965 as a method of linking related bodies of information to allow the user to browse through different databases randomly. Owl International’s Guide’ and Apple Computer’s ’HyperCard’ are two recent software products that embody these notions. Creative software designers are now using these same concepts to link different kinds of media - hence the term hyper-media.

How does hyper-media work? An example can be taken from the Grolier Multi-media Encyclopedia project, which uses a hyper-media approach to integrate separate text, audio and visual databases. In this product, the user can access the text of an article - say, the biography of Abraham Lincoln - and use simple features of the system to find pictures of Lincoln, orreadings of Lincoln’s famous speeches.

This article in turn may be linked to a "Time Machine’ database of historical events, which might lead the curious users to, say, the history of portraiture or photography and from there to a fully narrated audio-visual essay, and so on.

Chapter 1: Introduction

5

6 CD-l: A Designer's Overview

All this must of course be defined by the design team - clearly, a massive task when an encyclopedia is involved - but the concept is a relatively simple one. With CD-I, you can link any type of audio, video and text information on the disc to any other.

INTERACTIVITY - THE ’I’ IN CD-I

CD-I is founded on the concept of interactivity - that is, providing the user with a means to interact with a program in a meaningful and rewarding way. The success of the CD-I designer in developing compelling interactive programs will ultimately dictate the success of CD-I in the marketplace.

What is Interactivity ?

There are probably as many answers to this question as there are interactive applications. Using an automatic bank-teller machine, playing an arcade game, entering figures into a spreadsheet program, accessing information in an on-line database - all these are examples of interaction with a fully computer-controlled device. In CD-I terms, interactivity is the method used to interact with the content of a program which has been designed to respond in a very specific way to each decision, choice or request made by the user.

The CD-I designer’s role is to balance the objectives of the application with the degree of interactive control that is to be provided to the user. This balance must be carefullly struck at all times - while a flight simulator game might require continuous interaction from the user, an instructional program or pop music disc might only require occasional stopping and starting. (Remember, the user will purchase a CD-I disc for its content, not to get a sore thumb pressing buttons!)

How to use Interactivity

There is no magic formula for developing good interactive programs, although a full understanding of both the program’s content and the user’s needs and desires is a prerequisite. The interactive video experience can suggest some rules for the levels of challenge, reward, review and so forth which can be useful for certain kinds of program.

However, in general, only one rule need apply: whatever the goal of the program, make the journey to get there - the pathway through the content - as interesting and compelling as possible. The TV screen directed by a remote control device (a mouse, keypad or joystick) is the door into the content. It is the designer’s task to help the user step through that door and become immersed in a unique experience.

Interactivity: The Educator

Virtually all the experience for developing interactive materials (besides video games) comes from the development of educational computer software and interactive video. Educators have long known that interaction with audio-visual learning materials enhances the information transfer.

The success of interactive LaserVision training materials compared to traditional training methods is still further evidence of the potential for well-developed interactive programs.

Reports from training professionals indicate as much as a 40%increase in retention can be gained over standard training techniques. In an interactive program, the user is in firm control of the level and pace of instruction, and actively engaged in the pursuit of knowledge.

However, the motivation of the student and the job trainee are quite different from that of the average consumer, who is looking for entertainment or information, but is not compelled to enjoy and benefit from the experience. Consumers will not buy CD-I discs to get good grades (although a CD-I SAT disc could prove the exception!).

Do Consumers want Interactive Programs?

Some observers have remarked that consumers do not want to interact with their TV sets. Are they right? We do not yet know. Although a clear case for interactivity can be made in the training and education markets, nothing quite like CD-I has ever been offered consumers before, and no body of research exists to supply us with an answer. The best market feedback on which to base conjecture is the experience with video games and home computers. Fora short period video games were phenominally successful but, limited to ’shoot ’em up’ games with primitive graphics, they proved a passing fad. The early home computers also failed to live up to consumers’ expectations and quickly joined the video games at the back of the closet.

Were these marketing disasters a fair test of the viability of interactivity in the home? Hardly: it was too much to expect simple video games to have any lasting value, and the software produced for the early home computers was limited by the inadequate processing power and data storage capabilities of the hardware, and the crudity of their visual displays.

CD-I does not have these limitations. With its inherent multi-media capabilities, massive storage capacity , and the powerful processors built

Chapter 1: Introduction 7

8 CD-I: A Designer's Overview

into the player, CD-I provides a system for software performance which is well beyond existing home computer systems. With high quality sound and video pictures, CD-I represents a new information resource, delivering interactive programs on a wide range of topics and subject areas. CD-I should appeal to the same variety of interests that drive the sales of millions of books and magazines - certainly no previous generation of software has had this capability.

There are categories of CD-I software that we cannot yet begin to imagine, new combinations of information and entertainment waiting to be invented. The fertile minds of the creative community will respond to the challenge and opportunities of CD-I - the most powerful information system ever known.

Chapter 2: The background of CD-|

CHAPTER 2: THE BACKGROUND OF CD-I

The last chapter introduced the key concepts behind CD-I technology - interactivity and multi-media. This chapter presents an overview of optical disc technology, and CD-I (Compact Disc-Interactive) in particular. It traces the history of the medium and explains the different kinds of Compact Disc (CD) now available - CD-DA, CD-ROM, CD-V and CD-I. It also describes, in general terms, the technical and creative aspects of CD-I discussed in later chapters, as well as the market opportunities for this exciting new medium.

This chapter is essential reading both for those who intend to study this guide thoroughly - designers, programmers and others preparing to make CD-I software - and those who need only a conceptual overview - presidents and vice presidents, administrators, marketing executives and others not directly involved in the job of production.

THOSE CHILLY SATURDAYS

First, an imaginary look at CD-I as we may soon know it. Picture a Saturday afternoon in the late autumn. Wintery clouds block the pale sun, the air is crisp and cold. The chores are done for the day, (except to rake, once again, the eternally falling leaves) and there’s nothing left to do for a couple of hours. It’s a perfect time for sport. But, the summer sports have finished, there’s nothing on TV until tonight, and outside - nothing but fond recollections of warm days on the golf course.

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9

10 CD-I: A Designer's Overview

Chapter 6: Hot Shot Sports for Design Considerations

What a perfect time to try out that new edition of the CD-I golf game you picked up at the supermarket this morning. A few preparations are in order first - a snack, a soft drink, your favourite chair. Then, slap the compact disc in the player, and you’re off to the sunshine again.

So where to go? Slide through a few of those good-looking choice frames ... Hot Shot Sport! Yes, that’s you - look out Jack Nicklaus, here you come. You select golf from the list. Now choose a course. There are several on the disc, but the main thing today is to find sun and heat, so why not go for the big one ... that’s it ... the Augusta National, home of the Masters. It’s a chance to challenge golf’s greats - and it’s always warm in Georgia.

Before you tackle eighteen holes, why not sit back, finish off that hotdog while watching a ’mini-movie’ about one of the most famous courses in the world. That’ll get you in the mood, and besides you wouldn’t want to smear mustard on the putter!

Because the CD-I system is both a computer and a television, you have the best of both. The huge storage capacity of the disc offers a total experience in action and pictures. On the one hand, you can play golf with the interactive computer game: choose a whole round ora few holes. Whatever control device you use - keypad, mouse or any other - you have complete control over the animated figure on the screen, position, swing speed and precise moment of impact between the club and the ball.

On the other hand, with CD-I, the computer-animated character is combined with real photographic views of the fairway. The background is not a crude computer-generated graphic, but a series of actual shots of a world-famous course. CD-I also offers realistic high quality sound, to heighten the sensation: if you want to imagine yourself in a tournament, CD-I will even provide spectators who will follow your game with interest and appreciation!

You don’t have to work at it. If you need a break from the stress of serious tournament golf, youcan relax with some narrated video sequences about the course. They describe the history, course layout, and some of the great golf moments that have happened there. What a thrill to play a round on one of the most famous courses in the world - from your armchair, CD-I style.

The technology that can take a golf lover to Augusta or St. Andrews could equally take an amateur archaeologist through the Pyramids or an Etruscan tomb - or a gourmet cook into the great restaurants of the world

Chapter 2: The background of CD-I_ 11

for lessons from their master chefs - or a pop music fan into the studio to create whole new videos to their favourite tracks.

All this is possible through a machine no larger or more demanding than your VCR. CD-I truly combines entertainment with education, information with recreation, in a form that the whole family can use and enjoy for years to come. CD-I may seem like the technology of the future, but all this is possible now - because of work that began over twenty years ago.

ELECTRONIC PUBLISHING

Consumer Electronics Market

Traditional Consumer Electronics

Traditional Publishing Industry

Institutional Markets

The concept of publishing - that is, the distribution of information in printed form - has altered little over the centuries, even if production processes have changed greatly. However, the evolution of new communication media - radio, film, television, audio and video recording, as well as computing and telecommunications - has effected changes which now present wholly new concepts.

The one feature these new media have in common is that they are stored and delivered in forms that can only be read by a machine. They are unintelligible to the naked eye. The concept has grown from punched paper tapes and cards to magnetic tapes and discs, from factory automation to telecommunications and mass data storage, from entertainment through to every facet of information management. It is now possible to exchange information instantaneously, worldwide.

12 CD-I: A Designer's Overview

Yet only recently has electronic publishing touched the world of print, with the introduction of computer softwareand live on-line databases. These have tended to be used for large volumes of information - typically, financial, scientific or legal. It remained for optical digital discs to introduce the concept to popular communications.

OPTICAL DISCS

Optical disc technology represents a great leap forward in the quality, quantity and variety of data that can be stored,and what can be done with that recorded information. Furthermore, optical discs are robust, virtually impossible to pirate and so versatile that the technology has spawned an enormous variety of consumer and specialist applications.

The original research program led to three product development projects. The first of these involved data collection for company archival systems. This resulted in the Megadoc system which was the forerunner of the current Write Once Read Many (WORM) drives.

The other two development paths (leading to Compact Disc and LaserVision) were for distribution systems. So disc encoding and replication processes had to be developed as well.

The larger storage capacities and lower cost of production of optical discs resulted in the Compact Disc - Audio (CD-DA) breakthrough. However, optical media have been on the market since 1978 with LaserVision. This video version of optical storage has found success in the educational world in the form of interactive video discs. The digital compact audio disc (CD-DA) was launched in 1982 and has proved highly successful in the music listening world.

Optical media devices can be divided into two categories:

* Peripheral Devices: devices that can read the optical disc and transfer the contents read to an external decoder.

Both LaserVision and CD-DA from inception were conceived as systems.

Each of these types of device were originally intended for passive use. The ’systems’ family was extended in March 1987 with CD-I and in July 1987 with CD-Video (CD-V is an amalgam of LaserVision and CD-DA technologies, with a digital audio track added to the LaserVision disc).

Chapter 2: The background of CD-| 13

Optical Recording

Data Data

Capture Distribution

2

FUTURE

*) CD-ROM XA = CD-ROM extended Architecture

14 CD-I: A Designer's Overview

The original LaserVision and CD-DA specifications were also extended to form the ’peripheral’ family branch with the introduction of CD-ROM in June 1985 and LaserVision-ROM shortly afterwards.

Both peripheral and system variations are ’read only’ media, though only CD-ROM and LaserVision-ROM are named as such. There is a great deal of commonality among the LaserVision derivatives and among the CD-DA derivatives such as the same basic disc mastering and replication processes, and commonality of players for tracking and reading disc-bound information.

The use of optical media, like that of many other types of product, ranges from passive linear applications to fully interactive applications.

Existing media products like film and gramophone records could be regarded as fully passive. Television with a remote control keypad has a minimum level of interactivity requiring actions as simple as changing the channel. The use of other types of product ranges from passive use to full real-time interactivity in something like an automobile.

Optical read-only products span the same range. CD-DA for music listening, and LaserVision discs for films are fully passive products. At the other extreme are the interactive products of CD-ROM text databases, the interactive videodisc programs used in education and training, and the fully interactive consumer products of CD-Interactive.

All optical discs, whether intended for passive or interactive use, are based on the same principles. Coded information from a master recording on magnetic tape is burnt into a specially-coated glass master disc by a powerful laser beam. The beam records digital signals as a pattern of shallow pits and grooves on a long spiral path - rather like a conventional audio LP, but much, much denser (and winding outwards rather than inwards).

A series of copies taken from this glass master creates the metal stampers which are used to press copies in a special plastic. A fine film of reflective aluminium is laid over this, and sealed under a tough, clear plastic topcoat: this allows the aluminium to shine through, but protects the data well away from dangers of dirt, wear or rough handling. Optical discs are virtually impervious to damage.

A low-powered laser in the reading head of the disc player bounces a fine beam of light off the reflective surface of the disc through a network of prisms and mirrors to a photodiode which decodes variations in reflected light into audio and video signals, and computer data. The

Chapter 2: The background of CD-|

output of the player itself is compatible with existing domestic audio and video equipment.

COMPACT DISC (CD)

The Compact Disc (CD) is one type of optical disc technology. It offers a choice of formats for data of different kinds: CD-Digital Audio (CD-DA) for top-quality sound recording, CD-Video (CD-V) for video clips, CD-Read Only Memory (CD-ROM) for high-volume computer data storage and retrieval, and CD-Interactive (CD-I) for the first fully interactive combination of sound and pictures, computer text and graphics on one system.

* CD-DA audio discs measure 12cm (4.75") across, andcan carry up to 72 minutes of top-quality digital audio per side.

® CD-V discs range from a 12cm ’single’ with six minutes’ video and 20 minutes’ audio to 20cm and 30cm (8" and 12") discs offering 20 minutes and one hour of video per side respectively.

* CD-ROM discs are essentially computer storage media, holding up to 600Mb of data on a 12cm disc - 150,000 pages’ worth of text infor- mation and enough, say, for the complete white and yellow pages of the whole of the East Coast of the United States.

CD-I will hold up to 650Mb on a 12cm disc, but can handle data from a variety of source media, including natural video still frames (over 7800), audio (over 2 hours of top-quality sound or about 17 hours of simple narration), text and graphics (up to 150,000 pages’ worth) or, more typically, a combination of these under the control of the com- puter program also stored on the disc.

COMPACT DISC-DIGITAL AUDIO (CD-DA)

Compact Disc-Digital Audio (CD-DA) - what most people now know as *compact disc’ - is the most successful consumer product of the decade. CD-DA was launched in 1982 and by the end of 1987 about 30 million players and 450 million discs will have been delivered worldwide, with current manufacturing capacity for over 100M discs a year. Consumers embraced the new product because it offered very high quality sound reproduction at an attractive price: as the next compact disc systems emerge, offering multi-media and interactivity, the effects will be as revolutionary as the emergence of sound and picture recording themselves.

All CD technical specifications are based on CD-DA to ensure maximum compatibility as the newer products come onto the market: the same

15

16 CD-I: A Designer's Overview

Chapter 3: National Television Broadcast Standards

plants can make discs for all formats, the new CD-V and CD-I machines will play CD-DA discs.

ANALOG AND DIGITAL

Whereas other audio-visual media employ analog recording technology, based on variations in electrical current, CD-DA, CD-ROM and CD-I compact discs use digital techniques based on the more precise binary computer code.

The striking difference between a compact audio disc and conventional LPs and tapes illustrates one advantage of digital technology: the digitally encoded compact disc is virtually free from the degradation or noise’ inevitable in analog systems. This means not only crisper, cleaner audio recordings, but also a medium reliable enough to carry computer data as well as audio-visual signals.

INTERNATIONAL STANDARDS

To be compatible with existing television receivers and video monitors, both videotape (VCR) and LaserVision are tied to national television broadcast standards. This analog technology varies in both the transmission of the basic video signal and its color-coding. A tape or discmade for America, for example, cannot be played on a machine purchased in Europe.

What distinguishes CD-I as an audio-visual medium is that, like CD-DA, it is internationally compatible at its most basic level. As a result any disc will work in any player, anywhere in the world. CD-I employs digital technology. Wherever the system may be, a decoder within the player adapts the video signal to the type of receiver or monitor to which it is linked.

Furthermore, the standard was established by two leading manufacturers, Philips and Sony, who have licensed over 150 other companies to make discs and players.

Technically, this makes a CD-I disc as universal as a book or audio recording. However, CD-I has another feature: one disc can hold enough data to present the same material in several languages. Sound, pictures, text, graphics and computer programming are stored separately, and only mixed within the player during the actual presentation.

The disc’s large and flexible storage capacity can thus handle the text,

Chapter 2: The background of CD-|

pictures and sound to present a substantial program in a choice of national languages.

COMPACT DISC-INTERACTIVE (CD-I)

Natural Evolution 1985 Yellow Complete Specification

Physical Format Spec.

Multi Media (Consumer + Institutional) Full Compat.

Music Peripheral (C.E.) (Professional) Full Compat. Partial Compat.

The CD-I Full Functional Specification, or Green Book, was issued in March 1987. Amongst a number of ’logical requirements’, the following stand out:

Compatibility with the CD-DA specifications (the Red Book), so that a CD-I player can handle all CD-DA discs; (some CD-ROM and some more recent CD-DA players can also be upgraded to CD-I).

Compatibility with existing consumer electronic products so the new CD-I player can not only send sound through a home stereo, but also pictures as well as sound through the home TV.

The entire interactive multi-media presentation must be contained on one CD-I disc for playback on a CD-I player - unlike interactive La- serVison, there need be no extra computer and software.

Future proof’ technology that takes account of new and proposed standards, and allows room for later enhancements.

THE CD-I PLAYER

The CD-I specification defines the minimum standard or base case. This may be an integrated CD-I system or a separate decoder (or *black box’) to upgrade an existing CD-DA player. The basic drive is identical in all

17

18 CD-I: A Designer's Overview

Appendix C: CD-RTOS

compact disc players and includes control circuitry for the laser read-out head.

At the heart of the CD-I player is its operating system. This controls the rest of the system. CD-RTOS, Compact Disc - Real-Time Operating System, was developed to presentinteractive multi-media in ’real-time’ - that is, in direct response to the user in front of the screen.

The CD-RTOS, held in the player’s memory handles the basic management of the system, including the synchronization of audio, video, text, graphics and computer data pouring in from various sources for decoding and co-ordination into the final presentation on the screen.

On all compact discs, information is organized in tracks and sectors. Typically, on a CD-I disc all the material in one application is held in one track, which comprises many small sectors of individual audio, video and text. These sectors are played through the system at 75 per second. What appears on the screen, or is heard through the loud speaker, depends therefore on what these sectors contain. If they are full of audio, there will be no new pictures arriving at the screen; if they are full of video pictures, there can be no sound. So the effective CD-I producer must learn to balance the creative requirements of his program with the rate at which sectors can be played back - the amount of space available in the data channel. It is therefore essential for the producer to come to an early understanding both of the features available for program making and what space in the data channel each individual feature takes up.

CD-I AUDIO

CD-I offers a choice of quality levels for both audio and video: higher levels produce higher quality, but take up more space in the memory banks and in the data channels which send information from the disc to the player. The choice of quality level is vital since CD-I must typically handle a variety of data at any one time.

CD-I offers six audio options - three sound quality levels in either mono or stereo: A-Level (mono and stereo) is equivalent to the first play of a brand new high quality audio LP; B-Level (mono and stereo) is equivalent to the very best FM radio broadcasts, transmitted and received under optimum conditions; and C-Level (mono and stereo) is equivalent to AM radio transmitted and received under optimum conditions.

16 channels each of 72 minutes’ duration are available to play back the audio. A-level stereo uses 8 of them at once, so, allowing for some computer control data as well, a CD-I disc can contain just over 2 hours

Chapter 2: The background of CD-I

A-level stereo if there is nothing else on the disc; on the other hand, a disc full of C-level mono (using one channel at a time) and containing nothing else could produce a talking book over 16 hours long - or one program in 16 different languages.

In the critical trade-off between space and quality, A-Level stereo is best reserved for a musical interlude, while C-Level is used for commentary or background music when other data need a good share of the available resources.

CD-I VIDEO

CD-I also offers a choice of video picture quality: normal resolution for most video pictures; double resolution, for better definition of computer text and graphics; and high resolution, to meet future standards in digital television.

CD-I defines four main types of full-colour picture, and a choice of techniques to record and process these as economically as possible.

*Natural’ images such as photographic still frames use a video-based technique called DYUV, which offers very subtle and realistic color and shading.

Computer text and graphics can use RGB (Red, Green, Blue) compu- ter coding, but more often use a Color Look-up Table (CLUT), which creates a palate of up to 256 colors at a time.

Simple cartoon style drawings use Run-length coding for large blocks of single colour. These simple images can be processed quickly enough to create animation on the screen.

Where conventional video creates and records special effects when the master tape is edited, CD-I can simulate many effects from still pictures recorded on the disc. These include:

* cuts, wipes, fades and dissolves between images;

® scrolling horizontally or vertically;

© partial updates which change the picture in only part of the screen. These can be achieved through the use of CD-I’s four visual planes: a small ’cursor’ plane at the front of the screen, two full-screen planes and

a background plane for a fixed backdrop. A variety of images can be created by building up a composite picture using two or more of these

19

20 CD-I: A Designer's Overview

Chapter 4: The Design Brief

Chapter 5: Designing for Production

Chapter 6: Hot Shot Sports

Chapter 6: French Phrasebook

planes simultaneously. Clearly, there are considerable opportunities for the creative designer.

THE DESIGN PROCESS

In the early stages at least, it is likely that most CD-I projects will be based on successful work in other media, where the familiarity of the concept or title will attract consumers unfamiliar with the new technology.

Work may well begin with documents such as the client’s brief, the design company’s proposal, and the treatment and contract documents then worked out between the two.

Essential production documents will likely include a storyboard, a flowchart, and scripts for both narration and text screens. The storyboard illustrates both the appearance of the finished presentation and the interactivity mapped out in the flowchart. In CD-I as in interactive video, creative energy is concentrated at this stage, and not inproduction, for the scale and complexity of the job means that every detail must be agreed before the functional work of creating and assembling the component parts begins.

Many things may happen in parallel during the assembly stage: shooting original pictures, creating graphics and text screens, recording soundtracks, preparing computer programming and so on.

When all the material is brought together, it is encoded and compressed to create data files for testing on a simulator (a large computer with hard disc storage). Here it must be rigorously tested and evaluated, and adjustments made until all the interactive elements work smoothly together. Only then is it prepared for digital encoding and pressing as a compact disc.

Even then, the work of implementation and evaluation may continue for months or years, particularly in so new a medium, to learn from the users’ responses what people really want and expect from this exciting new medium.

This chapter has given an overview of the family of optical recording technologies and a short description of the salient features of CD-I. The following chapters will build on the brief look into CD-I that was presented here to include descriptions of the full range of media options and the stages in the process of designing a CD-I title.

Chapter 3: What CD-I cando 21

CHAPTER 3: WHAT CD-I CAN DO

The last chapter provided a broad overview of the background to the development of optical disc technologies and briefly described the features and capabilities of CD-I, This chapter looks at the wide ranging media palette available to the CD-I designer. Specific reference is made to the audio-visual concepts behind CD-I technology. More details of how CD-I provides these capabilities, in technical terms, are found in Chapter 7.

USING AN INTERACTIVE TELEVISION SET

The heart of CD-I lies in its name - interactivity: CD-I’s ability to search and locate the information requested by the user as whenever it is required. Also, CD-I can present this information in combinations of photographs, cartoons, music, speech and text, all of which can be called up at will by the user.

CD-Iis aimed primarily at consumers. It will also be extremely attractive to the professional and electronic publishing markets for such topics as education and training, catalog shopping and travel information.

CD-I has the great advantage of being able to do many of the things that other optical disc products can do, but at the same time offering many other features as well. It will both play super hi-fi music from CD-Audio discs and also display the massive amounts of text and graphics typically stored on CD-ROM discs. In addition, CD-I has been designed to meet consumers’ expectations of high quality video in still and moving pictures, photographs, cartoons and computer graphics.

The enormous repertoire apparent to the consumer is backed up by technical features which the designer must master in order to take full advantage of the opportunities presented by CD-I.

CD-I will play back in all current television standards and, through its interactive features, allow the user to pick and choose, mix and match. It also offers an enormous range of special effects and technical features. In addition to those commonly available in existing audio visual media like a choice of mono or stereo sound, video wipes and fades, and 3-D graphic images, CD-I also offers, in real-time, a choice of still or motion video, three different audio levels, three degrees of picture resolution, four coding techniques, and four separate image planes with and without transparency.

22 CD-I: A Designer's Overview

The description of these features presented in this chapter should give the designer sufficient background to sketch out the concept of a CD-I project. More detailed technical information is available in later chapters.

AN EXAMPLE: CD-I GOLF

The golf game described in the opening of the previous chapter makes use of the wide ranging options of a CD-I system.

A game of armchair golf combines the thrill and expertise of an arcade-style game with the high quality sound and visual images we expect from television.

The control device attached to the system - a specially designed remote control unit, a mouse, a joystick or perhaps a full computer keyboard on some - allows interaction with the animated character. Moving the cursor to the golfer’s hat, allows the whole body to move on the screen, aligning the direction of the shot. Moving the cursor to the ball, controls the swing. Holding down a switch or button starts the backswing, releasing the switch releases the foreward swing and tapping once again determines the moment of impact with the ball. The resulting flight of the ball has been determined by the skill of the player.

With CD-I, you don’t simply jump into a swing-and-hit game. CD-I golf is a multi-media experience. Earlier, we chose the Augusta National course in Georgia. Before we started play, we finished the hotdog and coke, while watching a documentary about the course.

Chapter 3: What CD-l cando 23

It was no different than watching a program on television. It showed us top quality photographic views of the course, aerial views of the hole layouts, even illustrated maps of the course with inset video sequences showing the great comeback victory of Jack Nicklaus at the Master’s in 1986. And the sound - marvellous! Narration, background music, even sound effects that were almost as pure and clear as listening to music without pictures from a CD audio disc which we could put on the same player.

Many of the effects that make CD-I programs a delight to watch and listen to, or even control and interact with, are created within the CD-I system itself. Whether you are planning a golf game, devising a tour through a museum, designing a language learning course or a music survey disc, understanding and using these features opens up a vast range of program possibilities for the CD-I designer.

AUDIO

CD-I audio can be played back through a home hi-fi system as well as through a domestic television set. It therefore not only meets existing hi-fi audio expectations, but also offers hi-fi audio in combination with high quality video images.

Quality Levels and Capacity

CD-Digital Audio (CD-DA) can store just over an hour’s worth of stereo sound of the highest quality on a single 12cm disc - but it devotes the whole of the compact disc’s storage and processing capacity to this end.

Whilst CD-I can of course play back CD-DA quality audio, space has to be made available, both on the disc and in the processing channels, for the other media - natural video images, graphics and text. The system offers the designer three quality levels of audio in mono and stereo.

The higher the quality level, the more data has to be stored and, at the appropriate moment, transferred from the disc. Therefore, the choice of quality level can be critical for some titles. It must be determined by the disc designer according the needs of his design, the disc capacity, and the space available in the data channel.

On many occasions, there will have to be a trade-off of quality level against transfer rate or disc capacity. It is therefore important that the designer understands from the outset the difference among the quality levels.

24 CD-I: A Designer's Overview

These audio levels are:

Data Channel Occupancy and Maximum Playing Time

DA A B Cc (Super Hi Fi) (Hi Fi) (Mid Fi) (Voice)

4 hours 8 hours

Max playing time: 1 hour

MONO

ec Max. playing time: 4 hours 8 hours 16 hours

¢ A-Level audio, equivalent to the first play of a brand-new high-quali- ty audio LP, but, because it is read by a laser beam, without any of the noise commonly created by contact between needle and disc. Stereo audio of this quality requires only half as much information as CD- DA, and thus occupies only 50% of the data channel, leaving the re- maining 50% available to handle other material (video, graphics and text). Mono A-level audio occupies only 25% of the data channel.

If the whole of the disc were to be filled with A-Level audio and nothing else, just over two hours’ pure stereo (or four hours of mono), could be recorded on a single disc.

© B-Level audio, equivalent to the very best stereo FM radio broadcasts, transmitted and received under the very best conditions. Stereo audio of this quality requires only 25% of the data channel and so leaves the remaining 75% of the data channel available for other material.

If the whole disc were to be filled with B-Level audio, over four hours’ stereo or eight hours’ mono music could be stored.

® C-Level audio is equivalent to AM radio when broadcast and recei- ved under optimum conditions. Audio of this quality in mono occu- pies only 6% of the data channel, leaving 94% for other material.

If the whole disc were to be filled with C-Level mono audio, over 16 hours audio could be played back.

Chapter 3: What CD-l cando 25

Where CD-DA handles a single channel providing up to 72 minutes of stereo sound, CD-I offers up to 16 channels in mono. Sound can be played continuously as music or narration.

In addition sound can be transferred from the disc to the player and stored as soundmaps in the CD-I system short-term memory to respond to interactive cues from the user.

The wide range of potential applications for CD-I will require a variety of audio effects from high-quality stereo music to mono voice-overs and narrations. The contribution made by the audio track at any one moment will help determine what quality level (and so, disc and channel space) it merits: this may vary from segment to segment within the program as attention shifts between audio, video, text screens and pure interaction.

In a music video, it may be worth spending up to half the available disc resources for high-quality sound; in a multi-lingual production, the multiple parallel tracks can be used for example to provide over an hour’s narration in 16 different languages - and allow the user to switch between these at will.

Soundmaps

In addition to taking the sound directly from the disc, short sound sequences can be stored in the player’s own temporary memory for ready access and processing without further reference to the disc. These sequences are known within the CD-I specification as ’soundmaps’.

Typically, a soundmap might be used where a short sound effect may be Chapter 6: Hot Shot repeated quite often during the course of a segment or program, e.g. in Sports: Audio

response to a user’s interaction. Once the soundmap is stored in the

decoder’s RAM memory, itcan be called up at any time, while the player Chapter 5: Basic

itself retrieves information of other kinds from other areas of the disc. Principles: System RAM

Soundmaps may be mono or stereo and at any quality level. Two mono soundmaps may be mixed to achieve one stereo soundmap, or sound data from the disc may be mixed with a soundmap to produce another soundmap altogether. Soundmaps may be used once or looped back as often as they are needed.

Soundmaps may also be used to improve the performance of a CD-I program by providing temporary storage. Sound can be pre-loaded from the disc at a convenient moment into one soundmap into order to release the whole of the data channel at a later moment for other material; or to be mixed and played back with the output from another part of the disc.

26 CD-I|: A Designer's Overview

Specialist Use

In addition to playback of stored sound, the CD-I system microprocessor can be used to generate its own sound. Specialist titles such as computer music applications could come provided with optional hardware such as a synthesizer keyboard to be attached to the system.

Audio Control

The stereo audio output levels may be controlled in a number of ways including, for example, panning from right to left, or attenuating under the control of the application on the disc.

VIDEO

CD-I has been designed to meet consumers’ expectations of the highest quality video in still and moving pictures, photographs and computer graphics. CD-I shares many features with other audio-visual media - particularly, specialeffects such as cuts, wipes, dissolves and so forth. However, whereas in conventional video production, these effects can be created and recorded only in the editing suite, CD-I can also create effects within the player itself.

It also has a unique combination of additional video features to offer the designer - playback on all international television standards, a choice of image resolutions, as well as access to four video planes.

National TV Broadcast Standards

CD-I will play back on all television broadcast standards. Currently, there are two main (incompatible) broadcast television standards used variously throughout the world, each with different screen display sizes. The system used in North America and Japan employs a 525-line screen updated at 30 times per second. This is known as NTSC. The PAL system is used in Britain, most of Europe, Australia, Africa and South America is based on a 625-line screen. A full picture is updated 25 times per second.

CD-I overcomes this problem of incompatibility. A disc which has been made to the CD-I standard for international use could be bought in New York and played on a machine in London, Leningrad or Bombay - just as for CD music discs.

Resolution CD-I provides three levels of video resolution just as it offers three levels of audio quality:

Chapter 3: What CD-l cando 27

Normal resolution is equivalent to the best picture quality obtainable on a normal broadcast television receiver; it is likely that most CD-I images will appear in normal resolution.

Double resolution is equivalent to the best picture quality obtainable on a standard computer color monitor, and provides better reproduc- tion of high-quality computer text and graphics.

High resolution is equivalent to the best quality digital picture gene- rated in the studio to AES/EBU standards.

These resolutions can best be expressed in terms of the number of picture elements (known as pixels) which appear across the screen both horizontally and vertically.

NORMAL RES. DOUBLE RES. HIGH RES.

Safety Area

The video picture tends to drift beyond the edge of the visible screen, particularly in older sets. This is known as overscan. Because of this, both television systems define a safety area in normal resolution 320 pixels across, which is 210 rows high in 525-line systems (NTSC), and 250 rows high in 625-line systems (PAL/SECAM). In broadcasting this

28 CD-I: A Designer's Overview

is known as the television safe title zone, and is virtually guaranteed to display adequately on all television receivers. When designing for international compatibility the CD-I designer should keep important information within adisplay area of 210 rows of 320 pixels (normal resolution).

Screen Resolution in Pixels

NTSC PAL/SECAM 360 384

a

Normal 240 280 720 768 Double 240 a 280 Nee 720 768 High 480 560 Compression

CD-I employs compression techniques to store and retrieve audio data as efficiently as possible. A variety of techniques are also used in picture coding to minimize the sometimes considerable demands of high-quality visuals.

Where conventionally-coded RGB graphics (Red, Green, Blue - the standard computer graphic coding system) might occupy 300k bytes of digital storage space and take nearly two seconds to load, compression techniques reduce this to around 100k bytes, loadable in less than a second.

Chapter 3: What CD-Icando 29

Coding Techniques

Four coding techniques are available to the designer. One, known as DYUV, is best suited to photographic images. Two, RGB 5:5:5 and CLUT are more appropriate for text and complex graphics. While, finally, Run-length coding is available for text, cartoons and graphics which use large blocks of color.

Natural photographic images are best handled through a compression Chapter 5: Disc Capacity technique known as DYUV, or Differential (or Delta) YUV coding. This

is based on conventional broadcast television and video technology,

where Y represents the luminance of a video signal, and U and V its color.

A combination of coding techniques based on compressing the color

signals, and coding only differences between consecutive pixels results

in a compression ratio of 3:1 in comparison with conventional RGB

coding.

When subtle shades and gradual changes in tone and texture arerequired, Chapter 7: DYUV Images such as in photographic images, DYUV is ideal. It is not suitable for text and those graphics which call for a crisper and less subtle display.

In cases where high resolution is needed for a natural image, a technique known as QHY (Quantized High-resolution Y) can enhance the luminance (’Y”’) signal to achieve this (the color resolution is sufficient already). Instead of direct high resolution DYUV coding, which would require four times the disc and memory space, high resolution is achieved by interpolation. QHY is used to correct the interpolated values where these differ significantly from the true values. This feature is not in the Base Case hardware specification.

Three coding methods are available for graphics: RGB 5:5:5, CLUT and Run-length coding.

RGB 5:5:5 is available only in normal resolution, and provides a Chapter 7: RGB 5:5:5 compression ratio of 1.5:1 - that is, around 200k bytes per full screen Images

image - by reducing the number of RGB levels from 256 to 32 (or 8-bits

to 5-bits) per RGB. This still leaves a range of 32,768 colors to choose

from. It is very good for graphics, and best suited to user-manipulated

graphics such as paint or drawing applications. Because other coding

techniques are available which compress the image at a higher ratio with

little loss apprarent to the user, RGB 5:5:5 is a relatively inefficient

means of coding.

CLUT, stands for Color Look-Up Table. This is the locationin memory Chapter 7: CLUT Images where a set of colors that the designer has defined is stored. CLUT is available at both normal and double resolution. Compression - at about the same 3:1 ratio as DYUV, and double that of RGB 5:5:5 - is achieved

30 CD-I: A Designer's Overview

Chapter 7: Run-length Images

by restricting the total number of colors available for any given image to a range of 256 or fewer, pre-selected by the designer from some 16 million ultimately available. The contents of the CLUT can be defined as having 256 levels each for red, green and blue, so the total number of colors available to the designer for a single image is 256 x 256 x 256 = over 16 million. The total range of colors available is greater than for RGB 5:5:5, but the number of colors on the display at any one time is limited. Since the human eye can only discern some 5,000 to 10,000 colors in any single image, this restriction in colors only becomes a problem for highly accurate representations of natural images where subtle gradation is essential.

When used at double resolution only 16 colors are available instead of up to 256 in normal resolution.

~—

Clut Length of Run Clut Length of Run Location (number of Pixels) Location (number of Pixels)

Run-length coding is very economical for certain types of graphic image suchas cartoons which use large blocks of color. Not only are the number of different colors limited, but also the number of color changes on any one line. Images like this can be stored, retrieved and manipulated on the screen very efficiently through Run-length coding.

Run-length coding uses the CLUT to define the colors to be used. The color choice per image is limited to 128 at normal resulution and only eight colors at double resolution.

The big advantage of Run-length coding is that a typical cartoon or line drawing will require only 10k to 20k bytes of data.

Chapter 3: What CD-Il cando 31

It is usual to store text in a compressed form using the character coding techniques of computers. However text can also be treated as an RGB, CLUT or Run-length coded graphic image. The CD-I specification defines a standard character set covering all Latin alphabet languages, including a number of special characters for currency symbols, diacritic marks, and so forth. Alternative character sets and fonts can be created transferring information from the disc into the decoder, so CD-I is truly multi-national and multi-lingual.

Image Planes Chapter 3: Visual Effects

Chapter 5: Screen Effects

Direction of view

oo

32 CD-I: A Designer's Overview

The. picture which the viewer sees on the screen can be composed of several image planes which appear one behind the other. CD-I offers up to 4 image planes. The first is a limited area 16 pixel x 16 pixel single color cursor plane. Behind this can be one or two full-screen image planes,which may be coded and displayed individually or together in any combination of DYUV and CLUT.

Alternatively these two planes can be merged into one plane so that an RGB 5:5:5 image, which uses twice as much data as the other coding methods, may be displayed.

Behind these planes is a fourth or background plane (not in use in the illustration) which acts as a backdrop in cases where all or part of both image planes are transparent. The backdrop may be a single color selected from a fixed range of 16. In some CD-I players, the backdrop may be replaced by an external video source.

The experienced audio visual designer will readily appreciate the enormous potential offered by this combination of planes.

Motion

The capabilities of CD-I have so far been described in terms of still images. CD-I is nota still image medium and the designer is encouraged to use motion where it is needed. However, because of technical considerations, care must be taken in designing motion material. It is important for the designer to understand the ways in which motion is achieved.

The first technical consideration is disc capacity. In computing terms, 650 Mb of data is an enormous store. In feature movie terms, however, one would be forgiven for believing that 7,800 DYUV video images will get eaten up in about 4.5 minutes. But of course a movie does not show 7,800 totally different images in 4.5 minutes - a lingering romantic movie might show only two or three basic images in that time with quite subtle differences between most frames. So disc capacity can only be calculated with precision when the actual information load - the quantity of separate bits of information to be shown on the screen - is known. This quantity can only be measured after the coding techniques and frame rate are known. This is another example of how important it is that the designer understand the technical requirements of CD-I - that means in the first instance reading right through Chapter 7 and the Appendices. This chapter is not the place to delve into so much detail. Suffice it to say at this stage that the designer should be aware that disc capacity is a

Chapter 3: What CD-I cando 33

constraint, but not a great constraint, if CD-I’s features are to be used to the full.

There are a number of ways in which images can be given motion when this is required.

Full motion on the screen can be achieved through partial updates - that is, a technique which changes the picture in only part of the screen at one time. The rate at which data can be transferred from the disc means that only about 13% of the screen can be updated fast enough to achieve full motion video.

However, cognitive full motion - that is where no subjective motion jitter or blur can be seen by 95% of the population - requires a minimum of 10 frames per second. The designer can achieve moving images at this rate covering up to 50% of the screen by using software coding techniques.

If an even larger picture area is required, full motion video can be displayed by using chroma key - a video technique frequently used on television in which one image plane of moving elements within the picture is electronically keyed over a still or scrolling image in the second plane. The size of image which can be achieve on CD-I depends, as always, on the amount of new information to be transferred from the disc.

A similar multi-plane technique is an integral feature of traditional cel animation in which the still elements of a scene are constantly re-used and a separate cel for the parts which move is laid over the top - typically at the rate of 10 to 15 frames per second. Run-length coding is a good technique to use in achieving full screen full motion animation since the typical Run-length image over the full screen may occupy between 8k and 15k bytes.

Again, the update rate will, of course, depend on the actual complexity of the images and the amount of space available for them, which in turn depends on the audio quality level and other data needed at the time.

Limited animation effects may be produced by re-defining the CLUT Chapter 6: Pop colors. A singalong sequence in a music application might show a ball Showcase: Screen moving across the screen to help the listener follow the words ofasong, Propertion

To simulate the movement of the ball as it follows the text, a series of

circular shapes are laid out on the screen, which can be colored using

locations in the color look-up table.

The balls can be made transparent by making each one the same color as the background. By successively changing the colors to yellow and back

34 CD-I: A Designer's Overview

to the background color, the ball appears to move across the screen. The CLUT contents are successively re-defined as the ball moves across the screen.

This simple technique, of course, may require a number of spare CLUT locations, but it can be very powerful.

Another possibility is dynamic CLUT update. By re-defining the CLUT from line to line down the display, the number of colors available in an image may be expanded to the limit that can be loaded into one field - about 2,000 colors.

By re-defining CLUT colors in these ways, it is possible to create a range of highly dynamic effects.

VISUAL EFFECTS

CD-Ican not only store and retrieve virtually any image as a high-quality still or graphic, but the range of special effects available within the system itself includes cuts, wipes, dissolves, granulation, scrolling and animation -enough features to rival most things to be found in modern video editing suites !

Single Plane Operations

Some effects can be achieved on a single image plane, but many require both. Single plane operations include cuts, sub-screens, scrolling, mosaic effects and fading.

Cuts

The cut - the sudden change from one image to another - is the simplest visual effect. In a single plane this means cutting between images stored in the player’s own temporary memory. A number of images may be held this way and used at a rate faster than any designer would likely want to use them.

Cuts can also be performed, of course, by switching directly from one plane to another.

Partial updates are rapid cuts in a single plane covering only part of the full screen image. Rapid cuts give full motion video.

Chapter 3: What CD-l cando 35

Sub-screens

7-bit CLUT

SUBSCREEN Sbit CLUT

\

Each image plane may be divided into a number of horizontal bands ‘Chapter 6: Interactive called sub-screens which can, if necessary, use a different coding Under Fives method. So images of different kinds can be shown together without

recourse to both image planes. In the example shown in the diagram, the

screen is divided in three parts: the main picture can be two DYUV

images and the band in the lower portion of the screen a text image using

double resolution CLUT or Run-length coding. The number of

sub-screens, their positions and their boundaries formed by horizontal

lines may be defined by the designer at will - in the extreme, each of the

525 or 625 lines could be a sub-screen. The advantage of using this

technique in the instance illustrated (a pattern recognition game for under

5s) is that it frees the other visual plane for a larger, more visible cursor.

Scrolling

36 CD-I: A Designer's Overview

Images may be scrolled horizontally or vertically. Simple examples include the vertical scroll of a picture of a clocktower from the base towards the top, or a horizontal scroll across an image stored in memory, perhaps a panoramic view much wider than the screen itself. In either case, the screen acts as a window onto the larger image. The relative positions of the image and the screen can be changed to facilitate smooth scrolling at any speed.

A combination of sub-screens and scrolling allows a central area to be scrolled between two fixed areas of the screen at top and bottom.

Mosaic Effects

Mosaic effects can be used for granulation and magnification of an image; basically, they involve reducing the resolution of the image through one of two mechanisms called pixel hold and pixel repeat. Partial updates of reduced resolution images covering a larger part of the screen can be achieved in this way.

Pixel hold retains the whole picture but reduces the resolution by making the image appear granulated. This is achieved by taking a pixel value and holding onto it for a defined number of pixel positions both horizontally and vertically. The different value (or colour) of the other pixels in the original image is ignored. This technique can be used with any image coding method, including DY UV and Run-length; the hold factor can be any number from 1 to 255, which may be independently set for horizontal and vertical directions.

Pixel hold is used for granulation effects where the size of an image remains constant, but a blocking effect is produced as shown in the figure. In this example, with a hold factor of two in each direction, every other pixel in both horizontal and vertical directions is expanded to four pixels on the screen, although the total image size remains the same. By changing the hold factor, the resolution of an image can gradually be reduced until it becomes unrecognizable, at which point, the image can be cut to another and the hold factor gradually reduced so that the new image now appears.

Pixel repeat magnifies a portion of the image without providing greater detail. Each pixel is displayed a number of times in sequence, as shown in the figure. A pixel can only be repeated 2, 4, 8 or 16 times. This technique can only be used with CLUT and RGB 5:5:5 coding so pixel repeat can be used for reduced resolution images, which require less data from the disc, or to magnify or zoom images.

Chapter 3: What CD-l cando 37

38 CD-I:A Designer's Overview

Chapter 6: French Phrasebook

In the diagram, a part of one image is magnified by a factor of two both vertically and horizontally, so each pixel in the original becomes four in the displayed image. Unlike pixel hold, only a part of the total image can be displayed. Partial updates of reduced resolution images covering a larger part of the screen can be achieved in this way.

Fade

The brightness or intensity of any image can be varied from black to full intensity through a range of 64 levels. Different parts of an image can be given different levels of brightness than other parts, so only parts of an image fade. It is more likely that this effect will be used to move from one image to the next in combination with two-plane effects.

Two-Plane Effects

All of the coding methods except RGB 5:5:5 allow for two separate image planes. The use of two planes, together with transparency, can provide a range of very useful effects including transparency in parts of an image, mixing of images, dissolves and wipes.

Transparency

The most obvious reason for providing transparency is so that the second image plane, or part of it, can be viewed through the first image plane. For example, a cartoon image in the first plane can be placed over a fixed scenic background in the second plane.

There are three methods of achieving transparency.

Chroma Key

Chapter 3: What CD-l cando 39

The first is the use of chroma key or color key, a technique which has been used in the video industry for many years. Red, Green and Blue, the RGB colors, for each pixel are compared to the color key value, which is defined in 8 bits of red, green and blue.

If the pixel color and the key color match, then that pixel is made transparent revealing the background. Since the color key function operates on the final RGB values, it is independent of the coding method.

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A second method for achieving transparency is the use of mattes. A matte is an area of any shape - regular or irregular - which is defined on the screen so that the area inside the matte is transparent and the area outside is not.

This is achieved independently of color key or any other transparency mechanism. A number of mattes can appear on the screen at one time and two mattes can overlap.

Transparent Pixels

In RGB 5:5:5 only, there is a transparency bit available for each pixel, so any combination of pixels can be made transparent.

Since RGB 5:5:5 does not allow the use of two planes, only the backdrop or external video can be seen when the transparency bit is used.

40 CD-I: A Designer's Overview

Dissolves

Before

After

As explained, it is possible to adjust the intensity of an image. By mixing the two image planes together at different intensities then translucency can be achieved. One example of this is the dissolve, where one image can turn into another by changing the intensity for each image so that one increases as the other decreases, and so one apprear to dissolve into the other.

The use of mattes allows mixing and dissolving to be restricted to parts of the screen defined by those mattes.

Wipes

Chapter 3: What CD-lcando 41

This is another way to change from one image to another which requires two planes. For example the figure shows a horizontal wipe, where one image changes into another by a wipe from from right to left. This can be achieved quite simply through the use of mattes where a simple rectangular matte, for example, starting from the right hand side of the screen and gradually moving across to the left hand side produces a wipe. Wipes can of course be horizontal or vertical and in either direction. Mattes can, of course, have different shapes and be varied in size, so for example a diamond shaped matte can start very small and gradually increase in size until the new image covers the full screen.

REAL-TIME INTERACTIVITY

This chapter has so far discussed the audio-visual elements in CD-I, but another essential feature is of courseinteractivity. Digital data on CD-I discs may contain audio, video, text or graphics. Data can also be used to control the presentation itself and to interact with the user in front of the screen. All this must happen in ’real-time’ (rather than, say the artificially fast or slow speeds common in computing), which makes special demands on CD-I technology.

Real-time Data

Audio and video are of course played from the disc in real-time. In addition, data of any kind from any part of the disc can be accessed - that is, found and retrieved - at random. This access is instantaneous if the new data is close by, and no longer than two seconds if the laser has to travel from one extreme position to another.

CD-I decoders can handle a variety of tasks in parallel and in real-time: this is essential if audio, video, text and graphics are to be synchronized to reach the user in the right order and at the right time.

Synchronization

Synchronization is very critical in the kind of complex multi-media presentation that CD-I offers. In the example shown here, the visual of the golf club swing must synchronize with a carefully-timed audio effect as the club hits the ball. The timing of the synchronization cue depends upon the instant that the player - acting through a remote control or other input device - determines, which in turn designates the exact moment of contact of the club on the ball.

42 CD-Il: A Designer's Overview

Chapter 5: Microprocessor

Chapter 5: Synchronizing to Video

This sound effect can be handled as a sound map pre-stored in RAM and played through the audio output channels at the required moment. The basic images are taken from disc and stored in RAM as drawmaps, and the animation sequences are handled by manipulation of the appropriate drawmaps.

Fairway

G Graphic Character Animation

Synchronization is controlled through data recorded on disc, and may occur in response to pre-recorded ’ triggers’ in the program, or the user’s spontaneous response to the program. These elements of the technology are explained more fully in Chapter 7.

USER INTERFACES

Interaction would be impossible without suitable user interfaces - that is, devices which allow the user to control or react to information on the screen by making choices, decisions and requests. An important element of the CD-I design task lies in the preparation of these essential user interfaces.

Physical Interface

The CD-I system specifies an X-Y pointing device as the main user interface. This could be a keypad, a mouse, a joystick, a light pen, a graphics tablet. It is always equipped with two trigger buttons which may be used in a variety of ways determined by the designer.

Chapter 3: What CD-l cando 43

The specific device chosen may depend on the application or range of | Appendix C: The applications used, and individual CD-I players may well allowachoice. Pointing Device

For example, a mouse is suitable when sitting at a table close up to the

screen for making selections or doing simple drawings on the screen. An Chapter 6: Interactive infra red keypad would be most appropriate for those listening to and —_ Under Fives watching a disc in television mode - from the other side of the room.

As an option, an alphanumeric keyboard may be provided with CD-I players. This will be necessary where the user is required to input long or complex textual responses.

For players which do not have a QWERTY keyboard, a simplified keyboard can be displayed on the screen and the X-Y pointer used to select characters from it.

Interacting with the User

A pointing device may be used to move the cursor around the screen. By controlling the cursor position, the user can select menu items or buttons, move level controls and so forth. Scrolling around an image which is larger than the display screen may be achieved through directional arrows or sliders on the screen.

The screen may therefore be designed to include certain areas, such as buttons - also known as hot spots or action areas. These allow the user to make selections, go back to a main menu or pause within an application. They may be displayed explicitly on the screen so that the user can see them, or the designer of a game for example may have decided that they should be invisible.

Interaction with the user is an essential part of a CD-I system and the designer must take great care to ensure that the display on the screen is always clear and designed in such a way as to make it inviting. The user must always understand readilty what to do - and, indeed, what can be done at any point in the programme.

CONCLUSION

This chapter has shown the range of features available to the CD-I designer. The combinations into which these may be woven may at times be bewildering, and certainly make the design process much more complex than that for any other audio visual medium. However, rich rewards await the imaginative designer who can master the techniques and who can conceive and develop programs that will set the world new standards of creative achievement.

Chapter 4: The Design Brief 45

CHAPTER 4: THE DESIGN BRIEF

Chapter 3 surveyed the media palette available to the CD-I designer. This chapter looks at the special creative and technical challenges posed to the designer by CD-I, and suggests some pertinent questions for the would-be producer to consider. It outlines typical stages in the design and production of a CD-I project, and discusses the skills and backgrounds required of members of the design team.

The previous chapter showed the wide variety of sound and picture making effects incorporated into the CD-I system. It is evident that a high level of planning and control is necessary if truly exciting and intellectually rewarding programs are to be created.

Like all successful publications of high quality, CD-I discs must be designed on the basis of a very clear understanding of the user and particularly what the user wants or expects from the program and the technology. So the very first task for the designer to address is not how to exploit the exciting opportunities that the technology offers but, rather, the age old issues of who will want the product, how it will fit into the market place, and what attributes of the subject matter make it suitable for the medium.

The successful designer is one who can answer these questions accurately, and as a result develop a product that will interest and excite the audience. CD audio has established the compact disc as a quality product in the minds of the public. CD-I must build on that reputation and success. It is therefore important that the first discs meet consumers’ expectations of a product which is new, and unlike anything else on the market: informative, entertaining, worth the money, and yet not too frighteningly modern or complex - in fact, somehow familiar.

DEVELOPING THE DESIGN BRIEF To develop a clear design brief, the potential CD-I designer will need first to address several key questions:

* How does this title fit in with the others already on the market? Does it duplicate, complement or supercede existing products?

® Who will want to buy the disc? - especially if they have to buy a CD- I player, too

46 CD-I: A Designer's Overview

DESIGN PROCESS

Chapter 4: The Design Brief 47

* How will the interactivity be used? How will the program retain its in- terest over many playing sessions? What will happen if the program is left unattended or the user is unable to respond?

As CD-I grows, the industry will be able to address these and other questions in more detail. However, the experience of other media - including interactive video - offers some guidance.

Why choose this title? Is it best suited to the market opportunities of CD-I?

CD-Ican combine high quality photographic images, full-color graphics, animation, text and sound in a range of qualities and presented in new and potentially exciting ways - and it can store huge volumes of this information, compactly in digital form on a single small disc: this we know.

The CD-I designer must decide whether any of these features adds real value to a product which could be made in another, more conventional, medium. The CD-I title must use CD-I’s unique attributes appropriately - and be readily accessible to the consumer. The temptation to exploit the technology simply because it’s there, or seek novelty for its own sake must be firmly resisted!

Particularly in the early years, adaptations from other successful mass market publications - books, video or computer software - will be important. People unsure of the technology will respond to a familiar title or concept, and this will form a bridge from the new product to established markets. However, to capture these new sales, it is important that CD-I really does add new dimensions to a product already successful in another medium. Otherwise, why buy the CD-I version?

The creation of a totally original concept for CD-I will present the greatest challenge to the CD-I designer - but the reward will be a purpose-built product which makes full use of the CD-I’s unique potential, in creatively imaginative ways.

A series of titles which make use of use the same basic design and production processes will help to diffuse the work and cost of developing software for the new medium. Typically these might include games, instructional materials, reference works and entertainment such as pop music programs or children’s shows.

48 CD-I: A Designer's Overview

Ask: ® Is this acommercial, promotable, consumer product? © What does CD-I technology contribute?

How does this title fit in with the others already on the market? Does it duplicate, complement or supercede existing products?

The first CD-I designers will waste effort if they try to produce a title which is already in production elsewhere, or does not fit into the range of products already indevelopment. There is simply not the room for two similar titles in such a new market.

Content providers, those who own titles already successful in other media, will look to CD-I as a means of re-exploiting the market. Fears that the new medium will destroy the market for the old product are ill-founded.

It has been established, for example, that the film of the book and the book of the film stimulate demand for each other.

The Grolier Multi-media Encyclopedia - one of many titles currently in production - is not a more conveniently shaped and packaged clone of the 20-volume print Academic American Encyclopedia, but an entirely different and complementary product providing education, information and entertainment in ways not previously envisaged.

Ask:

* DoI know enough about other titles that are being produced? Where can I learn more - from the publishing and AV trade press? From pro- fessional associations and groups? From the grapevine?

Who will want to buy the disc? - especially if they have to buy a CD-I player, too?

Chapter 4: The Design Brief 49

They are consumers who: ® like electronics for home entertainment (stereo, video, computers); * ownaCD Audio player;

® like to be the first on the block’ with any new product or status sym- bol.

Each potential CD-I project must be thoroughly analysed for its commercial potential in that market. Likely applications will include education and information, but entertainment is expected to lead the market.

The true multi-media nature of CD-I will allow designers to draw on the very best of published material and titles will not be limited to the types of electronic material currently available for home computers and in arcades.

Typical applications might include armchair travel and language courses with authentic sounds and pictures supported by masses of text; music tuition or a pop video that contains information and pictures as well as top-quality digital soundtracks, or even the Japanese ’karaoke’ option to switch off selected voices or instruments and supply the track yourself!

Chapter 6: Typical CD-I Applications

50 CD-I: A Designer's Overview

Chapter 6: The Grolier Multi-media Encyclopedia

Chapter 6: Country House Murders

Simple special effects and control commands could allow users to create original programming from the sound, pictures and text on the disc.

The initial target audience appreciates a product with educational value. CD-I can offer a constructive alternative to commercial television, and even something which encourages people of different ages to play or study together.

CD-I should prove a popular medium with children, with entertainment that is engaging, interactive and informative.

Ask:

How will interactivity be used?

The core of any CD-I title is its interactivity: it is the elegance - or otherwise - of this design that makes or breaks the program.

The user will have to be given the maximum encouragement to interact with CD-I. It must be clear at all times what is to be done next; there must never be an occasion when the user can get lost within the program; the user must always feel in control. Of course the designer may spring a few surprises - one would expect as much in a game or similar application - but this must not be so sharp as to disorientate the user.

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AINE LF ELGUPT

Chapter 4: The Design Brief

CD-I must also maintain the delicate balance between passive reception and true interaction. It is tiring to interact all the time - especially in programs which fully exploit the length and complexity permitted by CD-I’s storage capacity and multiplicity of effects. Interactivity must be perceived as true added value, and not merely a gimmick which becomes annoying when the novelty wears off.

Equally, the interactions themselves must be substantial: trivial rewards could put the new user off not only that program, but the whole concept of interactive home entertainment.

A key element in this design is the input device. A CD-I base case system can support an infra red keypad - a familiar device to owners of remote control television receivers - a tracker ball, a mouse, or a joystick which may be more familiar to owners of home computers. The choice for any particular application will depend on what room the CD-I player is in and how far the viewer is from the screen, but is crucial in establishing a friendly interactive environment. Similarly, menu design and other visual aids and prompts will also play a critical role; most computer users are familiar with the technique, but others will need encouragement and guidance. For example, menus can be hidden until they are needed. They must certainly be honed until they are as clear and straightforward as possible.

Action regions supported, for example by InVision, can be defined so that whole parts of the screen can be used to select routes through the disc: point to the door and give it a ’push’ and you’re inside. A whole language of icons must be devised to guide and prompt users through a

51

52 CD-I: A Designer's Overview

range of actions and responses. Pictograms and visual aids are especially useful in multi-lingual applications, and can streamline the appearance of menus and choice frames.

Audio prompting is a very immediate and friendly way to encourage interactivity. Technophiles can be frustrated by the slowness of audio prompting, but it has worked well for general audiences in LaserVision applications, particularly in point-of-sale projects.

Paradoxically, part of the elegance of an interactive application may lie in allowing the viewer to watch some segments passively. Effective use can be made of this ’Auto-play’ mode to sell the application, and to intrigue the user into trying new alternatives. It can also help the user to improve his performance by showing how the application can best be run. We do not yet know how consumers will react to interactivity at this level: what models we have - video games, for instance - are not always directly comparable with typical CD-I applications such as multi-media encyclopedias and programs to teach reading.

Ask:

¢ What is the most appropriate way of making interaction easy and fun? ° Is the user interface fit for its purpose?

DEVELOPING THE IDEA MAP

Having established the appropriateness of the title, medium and level of interactivity to the market and to the audience, the next task is for the designer to give shape to these ideas.

The design process may begin with a letter of agreement from the publisher or other ’content provider’. If the client originally submitted a brief for tender, and the production company replied with a proposal, there may now be a contract and a treatment agreed between the two.

The basic document which opens the door to pre-production will typically address the following fundamental aspects of the project.

¢ The Treatment,

Chapter 4: The Design Brief 53

DESIGN PROCESS

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54 CD-I: A Designer's Overview

TREATMENT

The starting point for production is the treatment. It is a narrative outline describing the proposed content or storyline, often written from the point of view of the user, including a description of how the interaction will appear to the user.

At this stage the precise design of the content has not been developed, so the treatment would present a hypothetical scenario, offering a preview of the possible program scope. It enables a publisher as well as the design team to be certain that the initial project brief has been understood with regard to what will eventually be produced, mastered and bought by customers.

Ata later stage of the design process this treatment may be redeveloped in a more detailed form, when the storyboard phase begins and when a clearer picture of the budget has been outlined. A detailed treatment is an essential document to brief scriptwriters and a potential source of publicity for the application.

THE DESIGN TEAM

Programmers

Graphic Content Designers Providers

CD-I demands a wide variety of design and production skills, some drawn from established media such as print and electronic publishing, computer programming and audio-visual production, others emerging as the technology itself develops.

Chapter 4: The Design Brief

Yet what CD-I demands perhaps more than any other medium is not only close co-operation within the design team, but also a sound understanding by everyone involved of both the technology and the individual disciplines which make up a CD-I program. Each must understand the technology to make the best possible use of its resources; each must also understand the potential (and limits) of disciplines other than their own, to choose the best medium for each message.

In CD-I, after all, the choice between video still, computer graphic, text screen and audio is more than a creative one, when storage space and speed of transmission are at issue. The way in which the user interacts with the program is both a technical and a creative decision which affects every member of the team from the software specialist to the screen designer and the scriptwriter. For a CD-I project to be truly interactive, the whole design team must appreciate the range of technical and creative elements involved at every stage.

Thus, in CD-I, familiar job titles like ’producer’, ’scriptwriter’, ’ graphic designer’ or programmer’ may cover arange of new and complex skills. Perhaps the early years of CD-I will offer talented and adventurous people the kind of opportunities that the early years of film-making and television did.

A Typical Design Team

° a project producer/director who will exercise creative control and ensure all materials are correctly integrated;

° a CD-I author who will control the overall interactive design and may write the script and the text screens as well;

° a designer of audio-visual material and software;

° a graphic designer to originate images and to design user interface screens;

To compete on the consumer market, CD-I programs will have to offer at least as much as established favourites in television, video, hi-fi and games - which means not just excellent sound and picture quality, but also significant entertainment value and ease of use for an audience not accustomed to high levels of interaction with recorded media.

Accordingly, those with a background in film, TV or corporate video will have much to contribute to CD-I - and some new ideas to absorb and existing attitudes to change, in the shift from linear to interactive media. Yet CD-I is in many ways like a book, and the traditional skills of writers

Chapter 5: Basic Principles

and

The Mechanics of CD-I Design

55

56 CD-I: A Designer's Overview

and editors as well as book designers, illustrators and art directors can profitably be transferred to CD-I. The publisher’s role is similar in both media.

BUDGET AND SCHEDULE

A target production budget must be developed at the very start. Although it will be far too early to develop this in any detail, block sums can be assigned to the major elements of production. These should include the costs of the interactive design and storyboards, image, sound and text origination, This will be constantly reviewed during the initial production phase until the completion of the storyboards, when a detailed and firm budget can be fixed.

The CD-I designer must have a clear idea of the cost of the project. This might seem to be difficult to calculate, at least until a few titles of different kinds have been produced. However, many parameters exist in traditional audio visual production to enable realistic target estimates for all but the final pre-mastering phases to be developed.

However, a thorough understanding of the technology is essential to create a design which can be realized with the money available. For example, the use of CD-I’s multiple soundtracks and image planes means that a single disc can be designed for a wide international market, but the additional cost of translating all the text and recording all the audio tracks must not be forgotten.

Nonetheless, once the parameters of the content, budget and the production schedule have been fixed, many elements of the project are as predictable as those of any electronic video program: salary costs can be calculated once it has been decided how many people will be involved and for how long, material resources from office space to technical facilities are predictable, as are the replication costs of the discs themselves - all familiar elements of any audio visual or publishing project to which firm estimates can be fixed.

There has currently been so little experience in CD-I production that it is not useful at this stage to assign outline costs to production. Many of the early projects being developed have budgets in the range $250,000 or more, while adaptions of existing products will cost much less. Large prestige productions developed from scratch will cost a great deal more. It seems reasonable to expect typical budgets to be around $250,000, somewhat higher than a single volume book, but much lower than low budget movies.

Chapter 4: The Design Brief

It is worth remembering that successful international book publishing ventures have made good profits on budgets well below and sometimes well in excess of these sums. Yet the potential returns from sales in a truly international market place (once it has fully developed) are likely to match the most successful books and movies.

In addition to the budget, a schedule of work, together with information on how that work is to be monitored and achieved has to be agreed.

Again, it is too early to be helpful about the length of design and production time. Simple conversions of existing interactive LaserVision products which did not seek to exploit CD-I’s unique features could be completed in weeks, while a high original, bespoke product - an intricate tour of one of the world’s great art galleries for example - might take years.

Whatever its length, the schedule must show, at specific critical points, where and how the review process will take place - who will be involved, and what issues are to be addressed at any particular time. Review periods may occur at fixed intervals (monthly or weekly, for example) or at the end of pre-determined production phases.

The initial project documents at the treatment stage are likely to set the terms for critical stages in the evaluation - say, completion of storyboards, during simulation, on delivery to the client, and after the program has begun to be used by its intended audience under real working conditions. In such a new medium, though, it is entirely possible that these criteria may be revised as the project develops.

The Production Process

In order to estimate the schedule of work and ultimately a projection of the cost of production, it is essential to have a clear sense of the phases that a typical application would go through as it passes from the idea stage through the design stages to eventual realization as a program on compact disc.

PHASE ONE: is the Idea Map - the development of a treatment, budget and schedule. It will also identify members of the design team and the probable outside content sources, facilities and studios that may be used in the production phase.

PHASE TWO: is concerned with the development of prototype storyboards and flowcharts. These will define the range of problems that

57

58 CD-I: A Designer's Overview

Chapter 6: French Phrasebook

Chapter 6: Hot Shot Sports

need to be solved before production can begin and typically consist of archetypal frames, stored in electronic form or as hard copy.

Prototype storyboards will show: ° screen design issues ° elements of the user interface ° a list of resources for sound and pictures ° an outline of coding proposals and other authoring issues.

The prototype flowchart will show: © the overall design for the interactive application, in both micro and macro terms ° any design issues which may affect the preparation of applica- tion software.

PHASE THREE: At this stage, problems are solved and definitive designs take shape. Electronic storyboards will present prototype frames, using master material for both sound and pictures. This material will later be encoded to the CD-I specification. The user interface will be comprehensively defined and the interactive flowchart will be finalized.

PHASE FOUR: Electronic storyboards can now simulate parts of the program. And the design and production parameters can be tested, using the most appropriate hardware.

PHASE FIVE: The shooting script will now contain a comprehensive list of audio-visual requirements, including how these are to be arranged. All the picture requirements will be listed according to their original format, and their encoding mode, and all audio elements will of course also be included.

A detailed budget and production schedule with reviews and income and expenditure schedules should be ready by this stage. A database management system will help to monitor all the individual production elements comprehensively throughout the project.

PHASE SIX: Production proper can now begin. After the video data has been ’captured’ (whether assembled from existing material or freshly shot, or a combination of the two), it must be processed and integrated. The video images are composed and reviewed, the predetermined coding is applied, and design personnel review the data which is then entered into the database monitoring system.

Chapter 4: The Design Brief

PHASE SEVEN: The audio data is composed, edited, and mixed down, and the appropriate sound levels are selected. The audio material is then reviewed in the same manner as the video data.

PHASE EIGHT: Finally, authoring - the creation of the control code - is undertaken when the design is fully implemented. All the audio-visual components are linked together with all text and user inputs.

The project is now ready to be reviewed and evaluated.

CONCLUSION

The development of the Idea Map provides a broad picture of the CD-I project into the design and production phases that stretch ahead. It sets up the control procedures that will help to maintain the continuity of the work that may be carried out on several fronts at the same time. With a well laid out document, the actual process of designing a CD-I application can begin with confidence that it can and will be realized.

The mechanical design tools essential to the coordination of a CD-I application will be covered in the next chapter. These include the nature of the CD-I authoring environment, some basic principles of data management unique to CD-I, and the way in which various effects can be combined.

59

Chapter 5: Designing for Production 61

CHAPTER 5: DESIGNING FOR PRODUCTION

Chapter 4 looked at the early stages of the design process, in which a general plan for the development of a CD-I project is outlined. This chapter will look into the next stage, in which the design enters a more detailed phase - that of storyboard development. The chapter will outline the proposed systems that will make up the authoring environment and looks at some basic principles of CD-I design and the way in which elements are brought together in the CD-I system to produce a program that attracts and holds a user.

DEVELOPING THE STORYBOARD

Once the first stage of the design process, dealt with in the previous chapter - the treatment, budget and schedule, and the design team - have been approved, the project moves into a detailed design stage. The task here is to develop one or more levels of storyboard that prepare the way for the production and authoring of program material into CD-I digital data. Applications in Chapter 6 show the types of storyboard style that may be used depending upon the stage in the production process. The techniques described here are a typical way to carry this out. However, different design studios may carry out the same types of task in different styles.

The storyboard page in the French Phrasebook application would beused = Chapter 6: French prior to the final authoring stage, when the precise nature of audio levels, | Phrasebook screen coding requirements and interactive branching must be known.

The example illustrated for the Hot Shot golf game uses a more Chapter 6: Hot SHot generalized descriptive form to convey an overview of necessary Sports information about screen layout, video planes, audio quality,

synchronization and the possible transitions to subsequent sequences.

These could change before they reach the final authoring stage.

Storyboards would usually be developed alongside a flow diagram that Chapter 6: French lays out the branching patterns at each stage of a sequence. It is essential Phrasebook

to know the pathways between stills or linear sequences, in order to

estimate processor requirements, images and sound sequences that must

be available for user choice, and the way in which users can escape from

a section or get assistance if confusion arises.

THE CD-I AUTHORING ENVIRONMENT

Before examining the detailed aspects of design itself, it is worth outlining the parts of the CD-I authoring environment that will become

62 CD-I: A Designer's Overview

DESIGN PROCESS

e _\ / PRINCIPLES | [| .

Chapter 5: Designing for Production 63

available to assist designers with the potentially complex tasks of working within data management threshholds for capacity and transfer rates. Some of these tools will be useful at the beginning of the design process. They will help the designer to simulate the general concepts of the program in rough form or as further briefing documents for graphic artists or live action directors. Other types of tool will be restricted to the final software authoring stages.

It is important to be aware that, at the time of writing, a variety of | Appendix C: CD-RTOS hardware and software design, production and testing tools are under 2d Invision development. A number of manufacturers and software houses have

indicated delivery of protoype authoring systems and software during

the second and third quarters of 1988. What follows is a description of

the principles being followed rather than a precise specification of any

particular hardware system or set of software tools.

The tools, collectively known as the authoring environment, will normally consist of a modular system, expandable from a single, low-cost workstation to a network of stations linked together into a complete production facility. It will be a distributed system, to allow teams of creative people to work simultaneously on an application, with easy access to common data and control information.

The authoring system will assist the designer in the writing of application code, the capturing of audio and video, and the editing or digitizing into CD-I formats, of these design elements. The edited data will be stored in the system’s powerful database, combined with control elements into disc files. Testing, another function of the authoring system, will involve playing back assembled files ona simulator. It will consist of a read-write storage medium and special hardware which will emulate a CD-I player. The simulator will ensure that the application is tested in a real-time interactive setting.

The Designer’s Station

The designer’s station will commonly be a single, low cost workstation with CD-I simulation capability used by a design team for storyboarding, scripting, program development and testing. It can be used independently, by attaching a local disc and/or tape streamer to the station. Audio, video and other data will be transferred in digital format to and from the station via tape.

The Production Facility

The complete production facility will consist of several workstations and dedicated audio and video servers. The facility will also use a studio server, which will consist of a number of large read/write discs, write

64 CD-I: A Designer's Overview

once optical discs for archival storage, and magnetic tape for output to the mastering plant.

Disc Building

The authoring system will be used for design, production and integration of an application through each stage of the disc building process. During the scripting phase, the designer needs to be sure that the elements of the application will not exceed the limitations of the CD-I player. For this purpose, an on-line Constraint Analyzer is being developed which can check the script against the known boundaries ofthe player. Disc band width, memory limitations, seek times and other key design considerations will be analysed using this software.

When design parameters have been set, the authoring system will guide the assembly process, which consists of data acquisition, presentation editing and disc building. Data acquisition involves the capturing, editing, and encoding of audio and video. Audio acquisition can be handled outside the CD-I authoring environment, as many studio facilities are capable of handling the complete digitization process.

Presentation editing links audio and video with programming. Simulation will be controlled by the presentation editing software, which will also provide data-specific editing tools, and tools for the building and testing of real-time records.

_ Lastly, disc building combines the control information with the encoded audio, video, text and application programming. These elements are structured hierarchically into records and files, and processed into forms needed by the master tape generator.

Standard Data Formats

The data used for CD-I applications will come from many sources. It will need to be translated into standard data formats to ensure compatability and quick, accurate data transfer. The standard formats include reading and writing routines and a standard library of access routines.

Scripting Subsystem

The term ’script’ is defined here as a set of structure, display and control commands which are used by the programmer in creating CD-RTOS modules. Simulators will read the script as the CD-I control and command language. The scripting subsystem will allow the designer to describe the program structure, controls and logical flow.

Chapter 5: Designing for Production 65

Audio Subsystem

The audio subsystem will accept digital audio, and convert it to any of the allowable CD-I formats. This will be accomplished by the application of digital signal processing algorithms. Digital to analog conversion will occur by the connection of a D/A converter to the output stages of a digital audio processor. Non-real-time synthesized sound will be produced by generating PCM files within the authoring system.

Video Subsystem

Images acquired from standard video sources will be filtered and processed into digital images. Standard image processing techniques such as noise reduction and color balancing will be supported. Manual editing and enhancement of images will be accomplished using digital paint systems. Once an image has been digitized, filtered and edited, it will be encoded into one of the accepted CD-I image formats such as RGB, CLUT or DYUV. Previewing the processed images will occur using a CD-I simulator.

The Presentation Editor

The Presentation Editor will assist in the creation and integration of real-time records. It will also link data into blocks and display these blocks for testing purposes. Both functions will use a simulator and CD-RTOS modules to support communication between the simulator and host system.

The creation of real-time records is one of the most important aspects of CD-I development. A real-time record editor will be involved in synchronization techniques, interfacing with graphics routines, and the generation of correct file interleave factors.

The Database Subsystem

The central problem in the creation of CD-I discs is the management of the massive amount of data which a disc will contain. The amount and complexity of data can be overwhelming, as it combines scripts, storyboards, CD-RTOS modules and source files, as well as multiple versions and types of images and sounds. Copyrights for all of these would belong to different people and organizations.

The database manager will provide a central control and management facility for coherent access to CD-I data. It will parcel out the data to the various utility programs and provide data locking to prevent two programs from modifying the same piece of data. As modifications are made, the database system will maintain a history of such changes. Access to data will be controlled, to provide data security and privacy.

66 CD-I: A Designer's Overview

Testing and Simulator Subsystem

The simulator will provide quick turn-around testing of ideas during the creation process. It will also test the final disc image before mastering takes place. In the basic authoring environment, the simulator will be a compiled’ facility. In the future, further development in the area of simulators may enable them to provide interpretive facilities. These would interpret database files to build the CD-I datastream, allowing faster interaction than the compilation technique, which requires each disc image to be rebuilt after every change.

BASIC PRINCIPLES

The authoring tools dealt with in the first section of this chapter will relieve the design team of some of the potentially burdensome calculations required to keep track of data in the CD-I system. Essentially, a designer wants to know what will happen on the screen or speakers of a television system and what will happen when a user participates in the various elements of interactive program material.

This is a major creative task. Software tools that can simulate the effects both at the general level and later at the specific authoring level, as well as provide feedback on data management, will release the design team to apply energy to solving creative problems rather than mathematical ones.

CD-I is not a form of video, like a VHS cassette player, but a computer-based technology: sound and pictures are simply aspects of a digital databank. That data can be transformed into video pictures, stereo sound, text, or it can remain in the digital domain to guide the direction of an interactive application.

The key to understanding CD-I and interactive design is to think about it as a computer process, rather than a television or print process. The design tasks can then be seen in terms of gathering and organizing different types of data that are made available to a CD-I user through the interactive computer interface.

While the CD-I designer need not immediately understand all the complexities of the technology, it is important to grasp the basic principles of CD-I design - the rate at which data can be transferred from the disc, the amount of data required for the various elements that make up aCD-I program, and the memory space available both on the disc and within the system. For example, how much space is required to store each type of data? How fast and to what locations can data be moved before

Chapter 5: Designing for Production 67

decoding and playback? What proportion of the available memory locations and data channels are consumed by each type of CD-I effect? What will happen on the screen while data is being located at a new place on the disc? How many tasks can be handled by the main processor?

In this section some of the elementary calculations needed to keep track of storage capacity and processing power are introduced. Design for CD-I requires a regular monitoring of both of these by estimating the data amounts involved in creating desired effects. Eventually they will be handled by authoring stations. Nevertheless, areasonable fluency with these numbers will give a greater depth of understanding about the types of effect that can be incorporated into CD-I progams. Appendix A gives a detailed account of the precise figures for storage quantities and data rates.

Basic Principles © Tracks and Sectors

* Disc Capacity © Data Transfer Channels ° System RAM

® Main Processor Power

Tracks and Sectors

In any CD-I disc, data is stored on a track of sequentially-recorded Chapter 7: CD-I Sectors sectors. A sector contains approximately 2k bytes of data. The precise

amount differs depending on whether it is Form 1 (usually audio and

video program material) or Form 2 (usually text and program control

data).

Chapter 7 deals with this subject in detail. What is important to remember here is that the CD-I player reads data at a constant rate of precisely 75 sectors/second, no matter where on the disc that data is located. This is equivalent to approximately 170k bytes per second (that is, 75 sectors multiplied by the precise sector size - which can vary slightly). So one sector (just over 2k bytes of program material) can be changed and interleaved in the stream of data coming off the disc at a rate of 75 times every second

A sequence of program sectors can be grouped together to produce a program module. The key to interactive program design is to break sequences into short modules that enable the user to couple them together through choices made at the screen interface.

68 CD-I: A Designer's Overview

Appendix A: Technical Specification Summary

Disc Capacity

The structure of the CD-I disc is explained in detail in Chapter 7, but essentially, the usable total storage space on a CD-I disc is 650 megabytes (Mb) of digital data - enough space for roughly 150,000 pages of text on a single disc.

Audio capacity is calculated according to the quality level used. One second of Level A stereo uses 85k bytes; Level B stereo 42.5k bytes; and Level C stereo 21.3k bytes. Mono at each level requires half these amounts. So if 650 Mb of disc space is available for sound, simple mathematical calculations can be made to determine how much of any particular audio level a CD-I disc may store.

Unfortunately, a megabyte is 1,048,576 bytes, not 1,000,000 bytes. Those not blessed with an understanding of computers must accept that there are 1024 bytes ina kilobyte and 1024 kilobytes in a megabyte (1024 x 1024 = 1,048,576).

So, to return to our task, if 650 Mb of disc space is available only for sound, then just over two hours’ of Level A stereo can be stored (650 x 1024 = 665,600k bytes divided by 85 = 7830 seconds = 130 minutes = 2 hours 10 minutes), or a prodigious 17.5 hours of Level C mono, but of course with no other data to accompany it.

Single visual images occupy various amounts of disc space depending on how much of the screen each fills, the screen resolution (normal, high or double), and what coding technique has been used.

It should be remembered that an image covering only part of the screen requires only a percentage of the space of a full screen image. For example, a picture occupying half the width and half the height of the screen would take up 25% of the screen (not 50% as the mathematically unwary might suppose).

A single full screen DYUV image in normal resolution and occupying a full 8-bit plane fills 360 pixels x 240 pixels in NTSC (384 x 280 in PAL). Each pixel needs 1 byte, so the mathematical calculation is quite straightforward: 360 x 240 = 86,400 x 1 byte = 86,400 bytes per full screen natural DYUV image in NTSC (107,520 bytes in PAL). The 86,400 bytes (107,250 bytes in PAL) can be rendered into kilobytes by dividing by 1024. The answer is 84.38k bytes (104.74k bytes in PAL) - call it 85 and 105k bytes. So, in simplistic terms, if 650 Mb of disc space is available for natural DYUV images, at least 7,800 different full screen DYUV images can be stored on and replayed from a CD-I disc (650 Mb

Chapter 5: Designing for Production 69

x 1024 = 665,600 kilobytes divided by 85 = 7,830). If only 25% of the screen is used, a CD-I disc can store over 30,000 separate DYUV images.

A single RGB image occupies both 8-bit planes and can be used in double resolution only. It therefore requires 170k bytes NTSC (210k bytes PAL) of storage space.

CLUT graphics occupy varying amounts of space depending upon the type and coding method. 8-bit and 7-bit CLUT, like DYUV, occupy full screen planes and require 85k bytes (105k bytes in PAL) of storage. 4-bit and 3-bit require only 1/2 byte per pixel or 42.5k bytes of disc space.

Using Run-length coding for 7-bit and 3-bit CLUT extends the capacity of a disc considerably. For example, a run of 10 pixels of one color - say, blue sky - would take only 2 bytes, one to indicate the color and one to note the length of run. The full economy becomes apparent in, say, a large expanse of a single color running for 50 lines at 360 pixels/line.

The maximum run of a single line is 255 pixels, however, setting the Run-length to 0 sets the distance to run to the end of the line. Each line would therefore need only 2 bytes of storage instead of the 180 bytes of a normally-coded 4-bit CLUT graphic. So 50 lines of one color would need 50 x 2 = 100 bytes instead of 50 x 180 = 9,000 bytes divided by 1024 = 9k bytes.

Of course, the actual requirement of any image depends on the data content of that particular image. With experience, it should be possible to estimate disc capacity fairly accurately. These concepts are explained more fully in Chapter 7.

Data Transfer Channels

The CD-I player reads one sector on the disc at a time and allocates it to a data transfer channel. There are up to 16 possible data channels available for audio information. Each other data type can have up to 32 channels.

Channels are a useful metaphor for the way in whichdifferent kinds of data must be interleaved into the data stream. For example, a television receiver may intercept all the available broadcast channels, although most TV sets can display only one at a time. In the same way, all the sectors in the data flow are picked up by the player and allocated to their respective channels, but only those called upon by the user during that particular run of the program will be used. (Although in CD-I, if not in most TV sets, more than one channel may be played at the same time.)

70 CD-I: A Designer's Overview

Chapter 7: CD-I Decoder: Audio Processor

Language Learning

ENGLISH VO. _

VIDEO CHANNEL

[_] German voice over in USE.

In the diagram, voice-overs in three languages are interwoven with background music and photographs. During the sequence, the user could decide to change from English commentary to German without interrupting the flow of music or pictures, since all three voice tracks are running in the data stream simultancously.

Data Transfer Channels: Audio Playback

All audio in the CD-I standard is digitally encoded until it is finally played back through analog amplification and speaker systems. This results in there being negligible background noise at all quality levels.

CD-| Audio

Level Name Bits per | Frequency | Percentage of CD-I (Requirement) sample | Response |of Channels} datastream used CD Digital Audio 44.1 20 16B PCM kHz a2 kHz | | Stereo sig (Super HiFi) | CD-| ADPCM Audio-Level

A (HiFi music mode) 37.8 8 17 2 stereo 50% (Equivalent to LP) kHz kHz 4 mono 25%

B (HiFi music mode) 37.8 4 17 4 stereo 25% (Equivalent to FM kHz kHz 8 mono 12.5% broadcast)

C (Quality speech 18.9 4 8.5 8 stereo 12.5% mode) kHz kHz 16 mono 6.25% (Equivalent to AM broadcast)

Chapter 5: Designing for Production 71

The critical factors in audio processing rates are the bandwidth (quality) that is reproduced at each level and the percentage of the data stream that is used.

A-level audio has a flat frequency response up to 17kHz (the limit of most discerning ears), while using only 50% of the data stream in stereo playback. C-level stereo, using only 12% of the data stream, is still able to reproduce excellent audio quality for most television applications. It is worth noting that B-level has the same wide frequency response as A-level but gains a slightly rougher quality by being stored in 4 bits instead of 8 bits.

Data Transfer Channels: Video Playback

Video data is transferred from the disc to the Image Stores before display on the screen. Video data must be mixed into the data stream with the audio and any software data that may be needed. The critical point to keep in mind for video processing is the time it takes to move a single image from the disc to RAM, given that it can only occupy that part of the data stream that is not used up by other data.

Both DYUV and 7- or 8-bit CLUT NTSC images require 85k bytes per full screen image. If no other data is passing through the channel at the time (i.e. no audio), it will take 0.5 seconds to load each image. This is calculated by dividing 85k bytes by the rate at which data can be transferred from the disc - 170k bytes per second. But if A-Level audio is playing, 50% of the data stream is already occupied, so it will take twice as long - approximately one second - to load each image.

[9] opaque

[__] TRANSPARENT

Chapter 7: CD-I Decoder: Video Processor

Chapter 3: Motion Vidco

72 CD-I: A Designer's Overview

Chapter 7: CD-I Decoder: Random Access Memory

Chapter 6: Hot Shot Sports: Audio

Creating motion requires the video screen to be refreshed around 15 times per second. Partial screen updates or run-length coding techniques reduce the amount of data required to store a single image in the motion sequences.

Each image can occupy only 170k bytes (the data rate) divided by 15 images/second, or about 11k bytes. Since a full screen DYUV and CLUT image requires 85k bytes in NTSC, then only about 13% of the screen can be occupied by moving images.

However, a series of software coding techniques have been developed that increases the amount of screen area available for partial updates from 13% to about 50% - and permits C-Level stereo sound to be played at the same time. These techniques effectively redistribute the coding parameters in such a way as to produce reasonable quality moving images instead of high quality stills. Using chroma key to confine the updates to the front plane can result in full-screen, full motion video with synchronized stereo sound.

System RAM

Aside from the permanent storage space on the compact disc itself, there is a temporary storage space within the CD-I system called System Random Access Memory (RAM), which offers a total memory space of 1024k bytes or 1 MB, divided into two banks of 512k bytes each. Data transferred to System RAM can be retrieved much more quickly than data which must be retrieved from the disc in real-time. As storage is temporary, everything transferred to System RAM is lost when the player is turned off.

Operating software in the CD-I system will use some part of the available System RAM space. While the main CD-RTOS operating system is contained in the system ROM, about 50K is loaded into system RAM when the player is turned on.

Application software requirements will vary according to the nature of the program, so a simple program may only need a few kilobytes of whereas a complex database retrieval program may use as much as several hundred. Some of this software will be loaded into the System RAM when the application begins, while other sections may be loaded and unloaded as the application progresses.

Most music and voice-over audio will be retrieved from the disc and sent directly to the Audio Processing Unit (APU), without using any RAM. However, some types of sound may be stored more accessibly as soundmaps in RAM for use at cued moments in the program or to await

Chapter 5: Designing for Production 73

the user’s actions: for example, a sound effect which signals a correct decision ina game. Effective use of soundmaps can help to mask the time taken for a disc seek.

Memory requirement for a soundmap is calculated on a percentage of Chapter 3: Audio: the data rate. The memory needed for a sound effect which lasts for 3 Soundmaps seconds at C-Level stereo is calculated by taking 12% (C-Level Stereo)

of the data rate (170k bytes x 12% = 20K bytes) and multiplying by three

seconds - about 60k bytes altogether. Once this is transferred to RAM,

it can be used as often as necessary in the course of the program without

recourse to the disc.

Video is the most critical user of RAM storage data as all visual images Chapter 7: CD-I must be loaded into RAM before being displayed on the screen. Each Decoder: Random Access bank of 512k bytes supports one video screen plane. Memory

Effects like dissolves or wipes require the second of the two pictures in the effect to be held in RAM and brought into play when needed. DYUV images use 90k (105k PAL) or about 20% of the available RAM space. When these images are loaded into RAM, their display timing is synchronized to the flow of the audio track, then they are unloaded to make room for new images.

Judicious design thinking is required to make efficient use of the limited RAM space available for both sound and pictures.

Main Processor Power

Video images can be synthesized or manipulated in the MPU before Chapter 6: Hot Shot passing to the screen planes for display. Drawmapsare spaces inmemory Sports: Action Areas that can be manipulated by the MPU. In the golf game described earlier,

the direction and size of the ball travelling down the fairway is

determined by the conditions of swing and the timing of the hit that a

player signals to the computer. A drawmap of the golfball held in RAM

is manipulated by the MPU and a trajectory is calculated with data

received from the user interface. Progressive variations in ball size and

screen position are calculated and displayed as the ball appears to move

down the fairway from the tee, rising in flight to meet the viewer’s eye,

then descending once again to land by the green in an excellent position

for the second shot.

The CD-I designer is faced with the task of creating applications for a consumer market whose expectations are based on broadcast television standards for sound and picture. The only real limitation to accomplishing that is the confined data flow, which hampers the use of unlimited full-screen full motion video. Managing the complicated data

74 CD-I: A Designer's Overview

storage and processing power restrictions within CD-I will be dealt with in the next section.

THE MECHANICS OF CD-I DESIGN

One key to effective design for CD-I is controlling the display of information in sound and pictures by managing the storage and transfer of digital data in the CD-I system.

CD-I is an interactive medium: the design of audio and visual images must be directed to the activities of the person using the application. Interactivity is not yet common in home entertainment and home education, so designs must allow for the consumer’s initial unfamiliarity - and, perhaps, nervousness - with the concept. People may not want to be constantly making choices, answering questions, looking for information or even playing games: they may want to watch a bit of television now and again.

These sorts of consideration should be allowed for in program design. The opportunity for a user to enjoy a variety of program styles will make successful programs. This section explains the various factors that must be brought together to present program material to the user.

Interface Devices

While the choice of interface devices of course varies widely across the range of potential applications and the degree of interactivity in any one, a basic device will have two buttons and a pointer to control a cursor on the screen. This might typically be a remote control pad, though other simple pointing devices might also be used. More complex devices might include a computer keyboard, a music synthesizer, a graphics tablet, and even special tools like light pens or bar-code readers.

Screen Design

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Chapter 5: Designing for Production 75

It is inevitable that expectations for this medium will be based on broadcast television standards, not only for picture quality, but also for pacing and many visual and conceptual elements. CD-I applications hardly need be modelled after trend-setting TV shows, but some awareness of the conventions of that pervasive medium is important. CD-I does offer many screen effects that help to create the visual style of broadcast television.

Magazines and television advertisements are also good models for CD-I screen design: the screen can be regarded as an electronic magazine page on which elements of text, photos, graphics and even full motion video can be combined for a variety of effects. And while one of the limitations of CD-I is that full screens of information require large amounts of data, it is not always necessary to change the whole screen at one time: small areas of change will accelerate the pace of the presentation without straining the data flow capacity. Ultimately, pacing depends on the frequency rather than the volume of change.

Screen Effects

Screen effects - what the user sees - are the visual palette of the CD-] designer, and require management of the different types of image coding to be displayed on one or both of the two 8-bit image planes.

Image coding is explained in Chapter 3. What is important here is the relationship between images in dual plane configurations and the restrictions that govern which planes are used to display certain types of image.

Dual-plane DYUV

DYUV images can be shown on both Plane A and Plane B, and these planes can be reversed while mixing images. However, problems of data rate arise in fast scrolling, and partial update effects (explained in Chapter 3) are difficult to achieve with natural images in CD-I. The subtlety of color coding in DYUV (and 8-bit CLUT) make it difficult for the system to calculate the necessary starting values, or their locations, for rapid updates to happen properly.

Chapter 3: Visual Effects

Chapter 3: Visual Effects: Scrolling

76 CD-I: A Designer's Overview

CLUT over DYUV

__}] TRANSPARENT

In this configuration, the 8-bit 256-color CLUT is taken up entirely in the foreground or Plane A, leaving Plane B to be encoded in DYUV. As the Color Look-Up Table is completely used by the foreground image, no space is left for any other CLUT-coded graphics. As RGB images require a full 16 bits, a single DYUV image is the only possible image that could be displayed on Plane B. The CLUT/DYUV combination creates a high quality natural background, such as a landscape or interior room, with a flexible CLUT graphic in the foreground. In a language ‘program, a graphic plate with a customer’s bill could be shown over a DYUV image of a French cafe scene to show through. Plane A could be partially updated to show changes in the bill if the customer wished to dispute the total.

The only advantage in using 7-bit CLUT in the foreground would be to increase the animation speed of the graphic by Run-length coding.

This configuration would be used to present text information on Plane A in front of a DYUV image. Text or simple graphic icons in a children’s entertainment program would benefit from double resolution without being affected by the reduction of color choice. 4-bit CLUT would also be useful for simple high-speed animation. -

Dual 7-bit CLUT

This is a very flexible image configuration. CLUT graphics can be displayed on either screen. Scrolling is less limited with dual 7-bit CLUT, and restricted only by available memory space.

Chapter 5: Designing for Production 77

3- or 4-bit over 7-bit CLUT

This configuration is best suited to foreground text or simple foreground animations over a more subtle graphic background. Both 3- and 4-bit CLUTs have a narrow color range and are best suited to large areas of animation. Remember that 8-bit backgrounds cannot be used in combination with other CLUT planes.

It is possible to use a 4-bit plane in the background if simplified colors are appropriate in both foreground and background - for example, for a text menu over a simple colored or fast-scrolling background page.

Dual DYUV with CLUT subscreen

In this combination, part of the screen appears as ordinary DYUV images, but another part is designated a sub-screen running the full width of the screen but only part of its height.

This sub-screen can be used for a complex graphic panel to control of | Chapter 6: Country the changing images on the remainder of the screen. For example, by House Murders using parts of the graphic toolkit, the detective in a mystery game could

control the path of a surrogate ’ walk’ through a country house where the

murder has been committed, interview suspects or gather clues.

Partial screens, requiring less data storage, save memory space in the graphic area and reduce the size of natural images to be updated in the DYUV part of the screen.

Controlling the Dataflow

The fundamental challenge for CD-I design is to bring together the design skills of existing media such as interactive video, television or book design, with the management problems of digital storage space and data flow particular to CD-I. To visualize the scope of possible applications, the CD-I designer needs to be at home with the calculations

78 CD-I: A Designer's Overview

Chapter 7: CD-RTOS

which keep track of CD-I data. The design factors discussed here are applied to potential applications in the next chapter.

Interleaving

Information stored at the beginning of each sector tells the CD - Real-Time Operating System what that sector contains - the type of data (audio, video, text, software), whether that data is real-time, to what channel the sector belongs, and so forth.

CD-RTOS directs each sector in turn to its appropriate processing location within the player. It acts like a traffic controller, directing each vehicle in the linear stream to the correct lane in order to make the most efficient use of space available. However, the traffic is not random since the CD-I program designer has some control over the types and sequence of sectors in the CD-I traffic flow, and thus the efficiency of CD-RTOS.

A-LEVEL AUDIO

In the diagram above, A-Level stereo audio is to be played with a series of dissolving photographs of a neighborhood in Paris. Audio of this quality requires 50% of the data stream, but for the playback of the audio to be timed correctly, each audio sector must be followed by a single

Chapter 5: Designing for Production 79

sector of other data such as the video data or possibly text or application software.

In this case, it is the audio that determines the speed of picture change, and the pictures are synchronized with the audio channel. Video requires approximately 37 sectors (SOPAL) to load each DYUV image into RAM. Of the 75 sectors per second picked up by the player, half are already occupied with the audio - leaving only half (or 37 sectors/sec) for video. At that rate, pictures are available at intervals of 1 second. In an actual photo essay, it is reasonable to assume that pictures do not have to change more than once every three to five seconds. Furthermore, the full screen need not change every time. Thus, this combination of audio and video data is well within the capabilities of CD-I.

If this application were part of a large database like an encyclopedia, or Chapter 6: Grolier a language phrasebook, then total storage space on the disc could affect Multi-media

the calculation: for example, C-Level stereo, rather than A-Level, would eed clopedia provide adequate sound quality and leave more disc space for other types — french Phrasebook

of information.

C-LEVEL AUDIO

80 CD-I: A Designer's Overview

Chapter 6: Pop Showcase: Disguising Disc Seeks

If C-Level stereo is used, only one out of every eight sectors in a sequence is required for the soundtrack. If pictures change by dissolving or cutting every four to six seconds, then other sectors in the data stream can be allocated to additional information that may be requested by the user, including completely different C-level mono sound.

Seek Time

The value of keeping a variety of programme choices grouped together in the data stream is the speed with which the CD-I player can respond to a user’s request for change. If the data is not present in the data stream, the player must seek it in another part of the disc, which is likely to disrupt the programme.

Seek time is the time needed for the pickup head of the CD-I player to move from one part of the disc to another, for the motor to adjust its speed accordingly, and for new data to be read and decoded in the system. CD-I discs revolve at variable rates depending upon the part of the disc that is being read - that is, they have a constant linear velocity (CLV), or constant data rate of 75 sectors per second. Moving towards the outside of the disc, the motor slows down; moving towards the inside, the motor speeds up. Picking up data stored within a 20 Megabyte (Mb) range (or within 3% of the disc) does not require the motor to change speeds significantly, so seek time is negligible. The total time to access new data may still be as much as one rotation of the disc (as much as 1/4 sec). At 170k bytes/sec, 20 Mb amounts to almost 2 minutes of real-time play or between 100 and 200 full screen DYUV images depending upon the quality of sound interleaved with the images.

Unlike interactive LaserVision, sound and picture can be stored in RAM and played through the system at the same time that the laser head is moving to another location on the disc to find the next sequence of material. Most seeks can be disguised in this way.

Synchronization

Various segments of CD-I program material travel along different paths and undergo different processes. Each type of data (video, audio, text, software) is broken down into units of about 2k and stored in sectors along the disc track. Thus, the playback of these sectors to the video and audio receivers must be synchronized to ensure that the audio track lines up with the right picture and that special effects in video or audio are correctly timed.

Within the data of any sector is a trigger bit, which tells the application software that this is a synchronization point and that something specific such as a special effect should happen here.

Chapter 5: Designing for Production 81

Synchronizing to Audio

In synchronizing with audio commentary, the video picture may change on a word or between specific phrases. The trigger tells the application software the exact time that the specific sector is being read by the player so the software can then cue the image change or any other effects that may be stored in RAM or generated in the MPU for that moment.

Synchronizing to Video

Ball Strike

C-level mono Ball Strike Club Swing —_ Audio Golf Course Ambience. Audio to RAM. Audio Playback par an —_—_—,_—,

Strike Fairway

Fairway Golfer Foreswing Trigger Scroll.

Graphic Character Animation Animation

The task is similar to that already practised in motion film or video. At the start of a sequence the audio must be correctly aligned with the video to ensure that a speech, for example, synchronizes with the lip movements of the speaker. Once the correct alignment has been made, sound and vision will proceed at a constant rate.

In CD-I, when the user may intervene to determine when a particular Chapter 6: Hot Shot action takes place, the task becomes more complex. In a game like the Sports: Audio

golf simulation introduced earlier, the visual of a golf club swinging must

synchronize with a carefully-timed audio effect as the club hits the ball.

The timing of the synchronization cue depends on the instant that the

player - acting through a remote control or other input device - designates

as the exact moment the club head contacts the ball. This type of effect

can be handled economically as a soundmap pre-stored in RAM and

played through the audio output channels at the required moment.

Timed Cues The CD-I system has an internal clock which can be used to generate Chapter 7: CD-I timed cues such as, for example, a limit on user response-time: if nothing Decoder: Clock/Calendar

82 CD-I: A Designer's Overview

happens within the designated period, the software proceeds to the next action on its own, perhaps advancing the programme, or perhaps shutting the system off.

Interactive Design

Interactivity covers a broad range of possibilities depending on the degree of user participation required. At one level, interactivity could keep the user guiding the program and responding to cues. The attention is active and highly engaged. Depending, of course, on the nature of the content, a linear sequence in an interactive application is usually best kept shorter than 20 or 30 seconds, before some kind of user action is required.

CONTROL GRAPHIC

KNOWLEDGE EXPLORER NCYCLOPEDIA ESSAY

At another level, interactivity may require the user to select a picture essay on Science, Art or Geography from an encyclopedia. The essay might then play for 5 minutes unless interrupted by the user to branch into other essays, or into a more interactive search through text information.

CONCLUSION

This chapter has covered the basic technical principles of CD-I design. Along with Chapter 4, a comprehensive view has been given of the Design Process from the initiation of the Brief, through the Idea Map, to the development of various levels of Storyboard. Chapter 5 looked into particular technical constraints that are specific to design problems in CD-I. Using this as a groundwork, the next chapter will present several detailed examples of CD-I applications that illustrate various design and data management concepts.

Chapter 6: Typical CD-I Applications 83

CHAPTER 6: TYPICAL CD-I APPLICATIONS

The previous chapters outlined the nature of CD-I multi-media and the factors which contribute to good application design. This chapter looks at some specific design concepts and how individual applications discussed in other chapters illustrate these concepts.

It is difficult to find subjects which do not lend themselves to development as CD-I discs. What may be even more difficult to realize is that when existing products are converted to CD-I they become entirely new concepts, quite different from the printed work, audio-visual program or computer software on which they were based.

An encyclopedia, for example, is no longer a series of articles, long and short, in alphabetical order, with pictures to illustrate a few. It may begin with a choice frame offering several voyages of exploration through picture, sound and text databases. You can study any topic you choose in a variety of ways - gaining a general overview in a short audio-visual essay, perhaps, before going on to see what more specific information is available, and choosing an area to study. You can pick a word - your own surname, for instance - and see how many times and where it is mentioned in the text database. You can even select information such as a picture, text and audio commentary, to create a short presentation of your own.

Similarly, the experience of watching a classic film, play, dance work or opera, for example, can be greatly enhanced through CD-I. The disc might contain, as well as the performance itself, critical essays about the work, short notes on key passages (which you can call to the screen at the appropriate time), interviews with key personalities, biographies of the principal performers and production team, and background information about the making of this production. You may listen to the original script or libretto, and call up sub-titles in the language of your choice. You can even dub out the stars and take over yourself, and make your screen debut opposite Garbo, Olivier or Callas!

The following are just some of the topics that lend themselves to CD-I. They certainly show the range and diversity of the CD-I publishing opportunity.

® pop music, movies, plays, dance and opera, enhanced as described above

* studies of famous people and events in history and popular culture

84 CD-I: A Designer's Overview

art and music programs which allow the user creative control games of observation/deduction, such as mysteries and adventures

educational games for children, to teach learning and social skills as well as academic subjects and knowledge areas

interactive movies and even erotica which allow the user or player to direct the action

games of skill such as bridge or chess, or enhanced versions of board games such as Monopoly

multi-media reference works such as encyclopedia and dictionaries

diagnostic reference books on specialist topics from family medicine to car repair

picture libraries and databases for amateur and professional collectors, scholars and hobbyists

games of general knowledge, wit and experience, such as trivia and word games

armchair travel guides and tourist books

guides to famous places and buildings, from archaeological sites to museums

maps, plans and navigation aids - including in-car systems *surrogate travel’ through fabulous places (real or imaginary)

arcade-style games demanding hand/eye co-ordination and quick jud- gement

educational material at all levels from pre-school to post-graduate language teaching for self-tuition or institutional use

industrial and commercial training material, both off-the-shelf and made-to-order

catalogs and sales aids, for use by customers and in co-ordinated sa- les presentations, and for staff training

And these are only a few ... A videotape has been developed which simulates some of these applications, keeping entirely within the ’Green Book’ specification. Chapters 4 and 5.developed a notion of the Design Process through three main stages - The Brief, The Ideamap, and The Storyboard. The following example applications illustrate various aspects of CD-I design issues presented earlier. The encyclopedia deals with the major issue of total storage capacity for one project on a single

Chapter 6: Typical CD-I Applications 85

disc. The Hot Shot Golf game will show an example of an early stage storyboard, where ideas are sketched out for such design considerations as screen style, program sequencing and possible interactive branching routes. The French phrasebook will show an example of a later, more specified stage in the storyboard process when the overall design is complete and ready to be released to production.

THE GROLIER MULTI-MEDIA ENCYCLOPEDIA

The world’s largest publisher of encyclopedias, Grolier, has already identified CD-I as the logical choice for a multi-media edition of their Academic American Encyclopedia. Grolier is currently designing the world’s first interactive encyclopedia on CD-I because CD-I provides an immense capacity for the storage of text, pictures and sound and because CD-Iallows the user to browse interactively. Even when stretched to the maximum search time, the CD-I encyclopedia will call up information much more quickly (and of course more accurately) than a reader can with the 20-volume original print version. Furthermore, CD-I can illustrate the text database with sounds and pictures, audio-visual experiences that add an entirely new dimension to information retrieval. The Multi-media Encyclopedia will tempt passive viewers to explore deeper layers of information through interactivity.

Designing the Interactivity

The key question in designing an encyclopedia is to be very clear about how the interactivity will work. Rapid and accurate text retrieval is an early priority, but many people love just to browse, and to have their curiosity stimulated by what they come across. Yet there must also be opportunities to take a break from the interactivity and be entertained. Audio-visual essays have been designed to provide hours of entertainment by taking the viewer on journeys around the vast amounts of knowledge by combining the text, pictures and sounds into short presentations.

Mode of Use

The text, picture and sound databases provide a natural foundation for the development of an overall structure for the various types of information to be contained on the disc. This will lead naturally into development of the first level of interactive branching to retrieve information from each of the areas.

With the Multi-media Encyclopedia, information will be divided into several inter-connecting databases (’Domains of Knowledge’) in a web

86 CD-I: A Designer's Overview

that enables the user to move freely among them. These databases include:

° A series of audio-visual essays on general topics within main catego- ries such as, for example, Arts, History, Geography, Science, Sports and Ideas;

* An audio database of speeches, sound effects, music and song;

° The full encyclopedia text itself - over 10,000,000 words fully index- ed.

Data Management

The critical data management issues for an encyclopedia concern absolute disc capacity rather than dataflow rates. However powerful CD-I may be, and however large its storage capacity, the megabytes still get used up awfully quickly when you are trying to cram an overview of the whole of human experience onto a 12cm disc!

Screen Interface

To allow entry to these various Domains, two types of screen interface are essential. One enables direct access to any of the Domains from the moment the disc is loaded. The other allows access from within one Domain to any of the others - a lateral structure. Each must be compatible with a simple input device like a mouse or tracker ball.

Menus

a

Menus provide instant access to any of the Domains so, for example, the user can pursue a specific topic or question. If the user simply wants to browse, the Knowledge Explorer offers a choice of short introductory essays on general topics. The menu here cycles a series of still images from each of the essays in the appropriate box, which actas visual stimuli to suggest what each essay contains.

Chapter 6: Typical CD-I Applications 87

Choosing just one of the essays begins a sequence of passive television viewing that can continue as long as the user wishes. The interactive aspect is up to the user to choose, otherwise the encyclopedia offers linear video without requiring constant or even intermittent attention.

Screen Effects

The short essays use the screen effects within the CD-I player to show photographic DYUV natural images and CLUT graphics.

Dissolves, wipes and screen montages give a television style to the presentation; however, as these effects are generated within the CD-I player itself, the individual images remain untouched, and can appear in a variety of forms - in the essays, or within any number of picture bank on various subjects.

This application could contain several thousand separate images, each of which could be used in several ways.

Graphic Control Panel

After simple access menus, the second type of screen interface is a flexible control panel which allows various degrees of interactivity.

If, for example, the user stops one of the Knowledge Explorer’ essays at any point, the image on the screen freezes and the ’control panel’ appears as a graphic and matte over the picture.

The control panel is coded as a 7-bit CLUT displayed on Plane A. Since the panel can be called up at random, the software must ensure that the image from the audio-visual essay is moved to the background if it is not already there.

Interactive Branches Several areas of the control panel are active regions’ and correspond to directions that the user may explore.

Touching the option ’Caption’ brings up a caption in the transparent area of the foreground panel. This contains additional information about the picture or subject on the screen. Each caption is interleaved with the data for its associated picture.

In the same way, the ’Links’ button brings up a list of options for connecting to other parts of the encyclopedia. This list is also interleaved with its associated picture.

88 CD-I: A Designer's Overview

?UTAMKHAMEN

AINE OF ELVPT

Although the pictures in the essay change slowly, and use C-level stereo for background audio and voice-over, the data stream is also occupied with other data elements which may not be used every time but which must be available to the user.

Domain Seeks

To reach some of the Domains offered by the Link option, or to research in the text Domain, the player pickup would have to move to another area of the disc, using a delayed seek time. This is acceptable as a major change is being made.

The CD-I Multi-media Encyclopedia is able to hold a vast amount of information on one disc: up to 10 million words, 3000 pictures, and three hours of sound - enough for a complete 20 volume printed encyclopedia with audio-visual essays and interactivity as well. However, the large volume of data being stored, and the complexity of access, requires careful management and design.

HOT SHOT SPORTS

The treatment for Hot Shot Golf has already been described in Chapters 2 and 3. Athletics is another topic that lends itself well to inclusion in the CD-I range of applications. The Olympic Games give pleasure to millions of television viewers around the world, but imagine how their pleasure can be enhanced even further with the CD-I Athletics database.

Chapter 6: Typical CD-I Applications 89

In the early stages of the High Jump competition, you can park the television picture carrying a live transmission from Seoul and call up the High Jump database. Who is the record holder ? What happened last time there was a jump off for gold in the Olympics ? Study the form of the contestants. Use the Slo Mo’ feature to step frame by frame though motion pictures of the last finals. Call up ’Chalk Talk’ and have the CD-I coach talk you through technique. So when the time comes for the jump off, your pleasure is greatly increased by the insight and understanding you have gained from Hot Shot High Jumps.

Back to golf. This application makes use of interactive computer animation as well as high quality photographs and ambient background sound. What is significant about this version of the game is that the graphics of the computer arcade game are combined with photos of areal course to allow the viewer to play alongside the professional. In fact, the storage capacity of the disc is sufficient to offer the player a choice of famous courses as well, from Augusta to St Andrews. The animation program for the game would use the same factors no matter which course was selected.

The accompanying outline storyboard shows the earliest stages of idea mapping, with sketches of a key image for each sequence of the game. These indicate the main types of plane configurations, sound quality, and the transition type (that is, whether the scene is part of a linear sequence or a pivotal frame allowing branching to other parts of the application).

The production tasks then fall into two areas. The first is to accumulate a database of photographs covering a representative sample of possible positions from which shots could be taken as a player moves through eighteen holes. The second is to develop an interactive game animation.

Photographic Database

Each game needs about 750 photographs, shot specifically for this project. For each of the eighteen holes, there is a tee shot plus five separate views spanning the fairway at 100 yard intervals, and a good

90 CD-I: A Designer's Overview

cprprosncrtitin: Hot Shot Sport sheer fg

Sequence: Main Chose Frame Plane A: CLuT-7 - Matte Plane B: Cuur-7 - tat serell

Source: Commission Graphic Time on screen: User Choice - max-hold 66 Sec Audio: b/map-theme 5 ste /sff 60sec

C- Stereo FX:

Transition: Branch - Sport menu - lursr On

Sequence: Match play Choyce frame Plane A: CLuT-8 - matte Plane B: Druv - still - 25%.

ice)

Time on screen: User thowce - max 305% Audio: ok

FX: Transition: Branch - Course Intro

Sequence: (surse Module 1: Augusta PlaneA: = CLUT-@ = - 100%, ae PlaneB: Off

cig Some Gommission Crephe Time on screen: User Choice - max 66sec. Audio: C- Moho

FX: ‘ : ~ Hole Caddy Transition: Branch Be nea se

- Return fo Choices Sequence: Hole Module - /S

Plane A: CLur -7 - menu 20% Plane B: dDYuv -(SStee - (00%

FE Source: Commisscan Graphic/Libary Photo

H Time on screen: User Chotee - max hold 30

Audio: C- mono ambience

FX: birds

Transition: - Game Branch > Pro shop

ea eee 5 (+

Chapter 6: Typical CD-| Applications 91

corproucrirtie: Hot Shot 5 port sheer 1D ie Soquence: Pro Shop - (5% hole

TE PlaneA: dyuv -/S* tee - /00%o

PlaneB: DyuV- sandtrap - 50% hey

Source: Commission Photo

Time on scresn: 4 see (mage

— C-skree V0. - Commentary FX: Ambience

Transition: /jpear disselve/return fy Hole Mod.

1 Sequence: Course Histo PlanoA: SyYUY Nick Lbas -756%125o PlaneB: § cLuT-7 Facthie fest

tm

Source Time on screen: £ Sec image Audio: C- stereo V.0.t¢ muste PX: crowd cheer

Transtion: 7 ineay disselve [return ble mod -

Sequence: Game -Ana:mation

PlaneA: CLUT-3 Golfer

PlaneB: § ceut-7 -/5%Hole/vertical scroll groph«c

SB Source: HPu sottwove | Commission avaphic

Time on screen: Lateractive . max hold 26sec Audio: C- mono ambience

FX: suing [hit [crowd

Brand. return / Itnear ty neat osttisn - bYuv

Transition:

Golfer Animation

Start Back swing Stayt Foreswing Ball Contact

92 CD-I: A Designer's Overview

selection of photographs on and around the green. Each photograph should give the player a good view of the next shot from the point at which the last shot ended.

These photographs can also be used in an informative way: the caddy menu, for instance, besides dispensing the chosen club, also offers advice from the club professional on the best way to play that particular hole. Short documentary sequences could relate anecdotes about famous golfers or famous tournaments at the course.

Screen layouts consist mainly of DYUV images of the course on the background planes with graphics of menus or the animated figure of a golfer on the foreground.

The Animated Figure

The golfer is an interactive animated figure which is handled by the microprocessor within the CD-I player (and remains the same no matter what course is represented in the photographs). The figure is seen from above (unlike the figure in the popular computer golf game) to allow the computer to spend its power on interaction with the user rather than ona complex graphic. With Hot Shot Golf, the player actually determines the flight of the ball by controlling the swing.

The golfer is a 3-bit CLUT animation in the foreground. In the background, the DYUV image looking down the fairway is changed to a 7-bit CLUT and replaced in the centre with a 7-bit graphic depicting an aerial view of the hole which will scroll vertically when the ball is struck.

Changing the DYUV view to CLUT keeps the background plane in the same coding system and CLUT scroll alleviates some of the difficulty of DYUV scrolling.

Chapter 6: Typical CD-I Applications 93

Action Areas

Two ’action areas’ have been determined for the golfer. The first is the hat: placing the cursor on the hat and holding the button down on the remote control device allows the player to align the golfer’s feet and thus the direction of the ball, taking into account factors of wind direction.

The second action area is the ball: when the cursor is moved to the ball and the button held down, the golfer’s backswing is activated; when the button is released the foreswing begins; at the moment the player sees contact between the lub and the ball, the thumb button is tapped once again.

Ball Strike C-level mono Ball Strike Club Swing Audio Golf Course Ambience. Audio to RAM. Audio Playback aS po yt

: Ball Fairway Golfer Backswing Foreswing Strike Fairway Graphic Character Animation Animation Trigger Scroll.

94 CD-I: A Designer's Overview

This is a point of critical timing, both for the player and the designer. The microprocessor has to deal with several calculation factors. One is direction, based on alignment of the golfer’s feet and by the point of impact: touching the button too early causes it to slice to the right, touching too late hooks it to the left, and correct timing sends it down the middle.

Another calculation is speed and distance of flight, which depends upon the amount of backswing and the club used. The microprocessor calculates these factors and displays a ball, which has been stored as a drawmap in RAM, increasing and decreasing in size as it flies down the fairway, coming to rest before the next shot. The speed of the scrolling fairway is co-ordinated with the speed of flight, so a poor shot may fly off the fairway to one side.

Audio

As audio is not critical for quality, C-level mono is used for a background of birdsong and the like. However, sounds such as the swing of the club through the air and the impact on the ball make the moment of contact more vivid. Four sound effects are loaded as soundmaps at the beginning of the swing: the loop of the foreswing cutting the air, the sound of the club hitting the ball, and a choice of crowd sounds appropriate to the quality of the shot - either a round of applause or a murmur of disappointment!

Of course, this type of interactive animation against a realistic background could be developed for virtually any single-player sport and, with some imagination, for team sports as well, with the user taking the role of a key player or even the coach.

COUNTRY HOUSE MURDERS

The murder mystery is a classic game, well suited to CD-I. The combination of interactivity and multi-media allows the designer no end of opportunities to thrill and suprise the audience. In the version designed for the demonstration tape, one or more players act as detectives trying to solve a murder in a stately country house; the computer randomly selects details of the crime, which change with every playing.

Surrogate Travel

The atmosphere of the house is created through a technique known as *surrogate travel’. The house has ten main rooms plus corridors, cupboards and staircases. As the camera travels through the house, a series of photographs is taken, at eye level, and at carefully graduated

Chapter 6: Typical CD-I Applications 95

intervals, to simulate the impression a real visitor would have wandering through the house and in and out of its many nooks and crannies. These DYUV images will ’cut’ in sequence on the background plane as the detective moves about the house. There is no jumping from room to room here: many things can happen to unwary detectives in the poorly lit corridors of old houses!

Movement is controlled by a CLUT direction graphic on the foreground plane. Touching the arrows allows the player to turn left or right or to walk forward.

Handling Disc Space

Storing photographs on the disc is a problem of disc geography. Images are sequenced so that the cuts can happen quickly and smoothly. Turns may require a short seek to the start of a new series of images. It would be preferable to jump at this point rather than after the turn and the start of the new ’forward’ sequence.

Possible false turns, where no further forward motion is possible, could be interleaved into the series: for example, the detective could stop in a corridor to look at a painting which might contain clues... or fall down the cellar staircase by taking too sudden a turn.

Icons

Routes through the house and the task of clue gathering is helped by various graphic icons in the detective’s ’tool kit’. At the start of each game, the detective is offered a choice of potentially-useful objects to

96 CD-I: A Designer's Overview

put into the kit - of course, there is not room for them all. For example, a plan of the house (which can be overlaid on any frame to show the player’s present location) would be useful- and so would a flashlight.

Other tools might include a cassette tape-recorder for interviewing witnesses and suspects, a fingerprint kit, a notebook and even clues gathered during the course of the investigation. As with many adventure games, the detective may not be able to carry everything at once, and may have to decide what to foresake, and where to leave it.

Audio

Audio quality is not critical in this game, but could be used for interviews, or random special effects like squeaking hinges and floorboards, or distant cries of distress, to add flavour to the hunt. The game might offer different levels of interactivity with, say, special sound effects to draw attention to important clues or even hints for the youngest or slowest players!

POP SHOWCASE

This application is about pop music, so the sound quality is a critical design issue. Pop Showcase is designed in two parts: the first concentrates on the music of a particular band or performer, the choice of A-Level stereo for optimum listening quality; the second is an information bank with details of the stars’ background, greatest hits, tours, gossip and so forth.

Chapter 6: Typical CD-I Applications 97

Since A-Level sound uses fully 50% of the data stream, the design of the accompanying screen displays is critical, particularly as the screen must seem to move frequently in keeping with the general tempo of the music.

Partial Screen Updates

A magazine style was chosen both to suit the lively tone of the program and to meet the practical need to keep the update areas small. As a particular song plays, DYUV images change in different areas of the screen as a pictorial collage to accompany the music, and also as a menu or table of contents for other material contained on the disc.

Disguising Disc Seeks

Highlighting any one of the images on the menu will stop the song and lead the listener into various related information areas, which might include a biography of one of the band members, or a scrolling list of hit records.

The music is used as background sound so the audio quality can be reduced to C-Level here as the graphic and DYUV components of the screen demand a larger portion of the data stream - and the viewer’s attention.

Moving from the Menu to specific information requires disc seeks. To keep the audio playback alive, the pickup head plays bursts of sound as it skips to a new area of the track. This is a way of disguising seek time - by making it audible!

98 CD-I: A Designer's Overview

Singalong A feature of Pop Showcase is a singalong section: as a song plays, the lyrics are displayed line by line with a bouncing ball that keeps time to the music.

The magazine format of the screen is maintained here, and greater interest is added by incorporating segments of CD videos coded in CD-I digital form onto the background plane. As the listener is probably singing, and not listening too closely, audio quality is again reduced to C-Level stereo,which leaves maximum room for the DYUV full-motion video and CLUT graphics in the stream.

However, as full-motion video is intended here, some careful calculations must be made to determine how the effect is presented to the viewer and what proportion of the screen can be occupied.

Screen Proportion

The foreground plane is a 7-bit CLUT graphic. It holds the scrolling texture plane with a matte through which a mixed DYUV and CLUT background in the other plane is visible.

The second plane through the matte is then divided into two subscreens: an upper partin DYUV containing part of the still pictures and the motion video, and the lower part in CLUT together with the rest of the still, the bouncing ball and the text. As the part of the still that is in the DYUV subscreen was CLUT coded originally, the joint between the two parts of the image is not visible.

The bouncing ball is created from a computer program within the CLUT subscreen.

The computer program for the bouncing ball and the scrolling of the front plane are pre-loaded into the program space in System RAM. The text bars are pre-loaded as drawmaps. While running the sequence, the partial update motion video and the sound are read directly from the disc, and synchronized to the program.

The partial update used here is 70% of the data stream. Thus 70% of 170k bytes/sec. yields 119k bytes per sec., which at 15 frames a sec. represents 8k (9.5k PAL) bytes/screen area/frame. In terms of screen area this is 8k (9.5k PAL) divided by 90k bytes (105k PAL), or about 9% of the full screen. This would be a rectangle just under 1/3rd by 1/3rd of the total screen.

Chapter 6: Typical CD-I Applications

The sound, C level stereo, takes 12% of the data stream. This is slightly under the full data rate, as the processor is heavily occupied with ball animation and the scrolling effects in this example.

As the video is not critical to the singalong sequence, this size of image would be very attractive in collage page format.

INTERACTIVE UNDER FIVES

Pattern, word and number recognition are learning concepts that all children under five years of age work hard to acquire. CD-I offers a unique and potentially highly effective means of providing attractive learning games.

One-to-one relationships with parents and teachers remain important features of learning at this age, but CD-I can provide hours of exciting supplementary practice. Bright graphic animations using 3-bit CLUT coding would enliven the acquisition of reading and counting skills no end.

Shape Recognition

In this sequence, a yellow bird is sitting in a tree created as a 77-bit CLUT in the background. A 3-bit CLUT sub-screen stretches across the bottom holding three silhouettes of familiar animals, one of which is the same as the bird sitting in the tree. An oversized cursor moves across a sub-screen at the bottom of the other plane. The object is to match the images.

99

100 CD-I: A Designer's Overview

The simplified cursor has been designed as very young children have difficulty co-ordinating a pointer in the usual way: thus, the cursor is incorporated into the graphics as a drawmap icon which moves about the screen in fixed or random patterns. When the icon is in the appropriate area of the screen, the child simply hits the specially designed large green control button.

The cursor shape is loaded into RAM. The microprocessor calculates the speed of the moving image and its position and displays the drawmap in that position on the screen, updating the image as it moves across. Certain areas of the screen can be activated so that, if the cursor is in that area and the button is touched, the system is cued to carry out the next action.

Sound is not critical in this sequence, so a background tune in C-Level mono is adequate, but for added interest, three sound effects are loaded into soundmaps in RAM as the scene begins - one of them is happy bird song. A voice-over acts as a guide to each game.

Each icon is active when the cursor appears in its silhouette area. If the button is touched while the cursor is in the bird silhouette, the bird will begin to flap its wings and sing its cheerful song.

As audio can be kept to C-Level, and the images are mainly animated graphics, CD-I storage and data rates are not strained - and nor is the production budget.

FRENCH PHRASEBOOK

CD-I offers a very flexible system for language tuition in the relaxed atmosphere of home or in an educational context such as a school. It has the capacity for simultaneous multiple language versions, live action dialogue scenes, and of course the interactivity that allows the student to practice in real-time simulations.

The CD-I French Lesson is patterned on standard home teaching systems which use books and audio cassettes to combine the pleasure of learning about a foreign culture with useful phrases for an upcoming business trip or holiday.

This particular phrasebook contains:

® typical conversations in cafes, streets, stations and the like;

® special phases for familiar situations such as asking for directions or changing money;

Chapter 6: Typical CD-I Applications 101

° the opportunity to learn new words simply by touching specific ob- jects in a scene;

* accumulation of useful phrases as they are learned in a scrolling note- book;

* a database of maps, museum guides and other tourist information;

A single phrasebook can be marketed in several countries since the use of C-Level mono audio allows simultaneous coding of voice-overs in four or five languages. Corresponding text screens can easily be provided as well.

pea fh pean Rey MZ

a!

C-LEVEL AUDIO

A five-minute picture essay on Montmartre begins with voice-over in French, but if the tired student feels that enough vocabulary has been learned already, this can easily be switched to another, more familiar language without interrupting the flow of the visual sequence.

102 CD-I: A Designer's Overview

Chroma-key Facility

Students learn new words and phrases through scenes which dramatize typical conversations, which they can control through interactive menus and some computer control programs.

Scenes are acted out in full-motion video - and in a screen area of the order of two-thirds by two-thirds. This is accomplished by using an additional software decoding method and CD-I’s chroma key facility: the actors are shot against a single color background which can be keyed over a still DYUV background in the C-I player.

Real-time Dramatizations

The waitress approaches the customer, who asks what he can have to drink. The student is presented with a screen menu of drink choices in the form of an 8-bit CLUT high quality graphic which wipes onto the screen, replacing the closeup of the waitress on the front plane. The student can choose a drink.

Routes through the options available to the student are controlled by computer program code which directs the branching of the operating system to the appropriate start locations of each dialog sequence. Each set of responses is coded onto the disc, one after the other, and each lasts three or four seconds.

Chapter 6: Typical CD-I Applications 103

There are 3 possible sequences on the drinks menu:

° A menu of six choices appears and the student chooses café au lait

° First branch - first choice: the system moves to the beginning of the sequence for café au lait: Customer: ’I would like a café au lait.’ Waitress: ’A café au lait, very well;

° The waitress confirms the customer’s request and the whole menu reappears.

(Her response is useful both to the learning exercise and to shift the angle of view back onto her. After the student’s next interaction, the customer can reappear at a new angle and appear to exchange remarks with the waitress. Changing the angle of view this way avoids jarring cuts to a new version of the same scene.)

© Second sequence - with the second menu in view, the student can re- consider and selects jus d’ orange. © Second branch section - all choices made after the first one: the sys- tem moves to the start of the jus d’orange sequence: Customer: ’No, I think I would like an orange juice after all.’ Waitress: ’Ah, you would prefer an orange juice?’

* Third sequence - this time the student confirms by re-choosing the orange juice: - Customer: ’Yes, please.’ Waitress: ’Very good, I’ll get it for you.’

Of course, the student could work through all six choices on the menu without exhausting the patience of the long-suffering waitress.

104 CD-I!: A Designer's Overview

TITLE: Bienvenue 4 Paris Sheet: 8./7

@m/NTSC Normal/dbiga/Double Producer: Caeeutey Section: Dialogues Sequence: (Cyfe ~ Drinks

PLANE A

Visual: Motion Video

Update: /$, i Sec

% screen: 76 PRY,

Customer + Waitress

Source: Chroma key - Studso

PLANE B Visual: Stell Photograph Update: Hold

% screen: [99 %

ae Sa ne

Source: (Commission

TRANSITION linear/branching

TIME ONSCREEN: 5 $¢¢ /module

AUDIO level: € mono/etesee

Drinks = Lip Synch.

TRANSITION EFFECT: Linear Update

2. Laterrupt to freeze

SCRIPT

Linear Nest frame Mom Jeon Bar Cate menu

Cate Zeon Bar

W: Bonjour ,Mansreur, vous desires 6: buest-c4e que vous aver comme horssons

Cate ambuence - S/map

Chapter 6: Typical CD-I Applications 105

CD-1 PROJECT TITLE BiNVENUE A PARIS sHeeTt: 9./9 SECTION: DIALOGUES SEQUENCE: CAFE / DRINKS

VIDEO: General Latroduction

LEAD IN CHOICE:

PHRASES WALLET DIcrionaRy DIALOGUES GUILE Boon NOTE ROOK

SeLecTe Dratooue '

CHOCCE: DIALOGUE CAFE STREET POST OFFICE RAILWAY HoTec BTC.

se CAFE’

SEQUENCE ModUuLe

vioeo: CAFE (NTRO

RETURN

CHOICE: PRINKS MENU & OPTIONS

ALL CHOLCES

1°*7 CHOKE APTER 13° CHOICE

VIDEO ! OURIRMATION VIDEO 2

DIALOGUE: NEW CHOICE OfALOGUE

, q 04. ‘CAFE AU CHIT €9.'Jus D' ORANGE

VIDEO 3 DIALOGUE: CONFIRMATION - PReviou £ CHorce

CURSOR (INTERRUPT

LEAD OUT CHOICE:

(CON BAR MODE; CAFE SCENE

VIDEO: MODE: ACTIVE SCREEN!’

106 CD-I: A Designer's Overview

These optional routes can all be laid out on the disc in reasonable proximity to each other. Each section contains about six double phrases in the exchanges between the customer and the waitress, each requiring three or four seconds of real-time decoding.

Basic programming technique can identify a choice from one of the action areas on the menu, then seek the first sector of the appropriate sequence.

The customer could also ask for the bill, the option at the bottom of the menu, which would initiate a graphic and voice-over. (The wrong bill might be presented, which the customer could dispute by highlighting the amount where it appears on the screen.)

The customer can pay the bill through the ’wallet’ menu on the icon bar at the bottom of the screen, by pointing toa note ofa given denomination, which calls up an appropriate audio response:

¢ From several denominations, the customer selects one, saying: ’Here are .. francs’. Each possible phrase is so short that all the possibilities can be loaded into RAM for instant response time.

The icon bar (a 3-bit CLUT graphic sub-screen) provides access to the

many different modes of operation in the lesson - a dictionary which

activates areas of the screen to provide an illustrated vocabulary, a

guidebook to Paris, even a scrolling notebook to copy the last set of

phrases for easy reference.

The attached flowchart and storyboard page show how part of this sequence might be laid out. The storyboard page lists most of the key

Chapter 6: Typical CD-I Applications 107

factors in the design of this module such as plane configuration and percentage of screen occupied. Transitions are indicated at the bottom showing the next positions that the progam could move to depending upon the user’s choices. This takes into account both linear and interactive branching sequences.

Cop) INTERACTIVE 4)

4 Choice Sector 2 Choice Sector 3 Choice Sector

The flowchart page is a module sketch diagram used to plot the possible actions. It forms the basis of a briefing document for the software author. The precise routing of choices for the phrasebook application may change several times before the final version is tested and proved successful.

CONCLUSION

This chapter has described a range of applications as a way of further informing the reader of specific design concepts. In these early days of CD-I, applications will tend to be based on familiar resources - material from other media which can be converted to CD-I, or projects modelled

108 CD-I: A Designer's Overview

on established formats from publishing, broadcast television or AV and computer software.

CD-I is powerful because it is a multi-media publishing vehicle. All the media can be integrated and everything is in the digital domain. CD-I is the first medium to combine the impact of video with the power of the computer in the same language of digital code. This demands new ways of thinking about information storage and retrieval. This powerful new medium will change our lives and the way in which we do things.

Chapter 7: How CD-I works 109

CHAPTER 7: HOW CD-I WORKS

For those readers wishing to understand more of the technical aspects of CD-I after having read Chapter 5, this chapter describes the CD-I Specification, or Green Book, in more detail. The subject is approached from the computer-orientated aspect of the technology.

A description of the disc structure and organization is provided, including file structure, the design of a typical CD-I decoder and a brief description of the Compact Disc Real-Time Operating System, CD-RTOS. Further information on CD-RTOS is given in Appendix B.

DISC STRUCTURE

The organization of a CD-I disc is designed to be compatible with existing CD-Digital Audio (CD-DA) discs and players. CD-I is based on the highly successful CD-DA specification and is a complete system specification, which includes the encoding process, disc content, and the CD-I player. CD-ROM, in contrast, only specifies a division of the disc into sectors. The encoding and decoding methods are not defined, and are to the individual applications developers to establish.

Disc Organization

The CD-I disc can contain some 650 Mb of data in any combination of audio, video and computer information. All compact discs - CD-I, CD-DA, CD-V and CD-ROM - contain a lead-in area, a program area and a lead-out area. The program area of a CD-I or CD-DA disc can hold up to 99 tracks, numbered from 1 to 99, and while a CD-I disc can include CD-DA tracks, the first track must always be a CD-I track. Any CD-DA tracks on the same disc must appear after the CD-I tracks. Typically a CD-I disc will contain one CD-I track plus, optionally, one or more CD-DA tracks. Each track can be of any length between 4 seconds and the total available program space.

CD data (as opposed to music information) can be recorded in two modes: Mode 1 - which is used in CD-ROM - contains extra error detection and correction codes, and is suitable for data which are highly sensitive to errors (such as computer databases). Mode 2 is suitable for information such as audio and video data, which is not so sensitive to errors; however, the CD-I specification has defined two specific Forms within Mode 2, Form 1 and Form 2. Form 1 also contains extra protection for sensitive data. All CD-I data are recorded in Mode 2.

110 CD-l: A Designer's Overview

TRACK 1 TRACK 2

166 2250 2250 Message Message Message | CD-DA Sector Sector Sector

The track organization - which is mandatory for all CD-I discs - is indicated in the figure. The beginning of the program area (that is, the start of track number one), opens with 166 message sectors which contain CD-DA information only.

The disc label (described later), comes next, followed by 2250 message sectors (or 30 seconds), after which comes the CD-I data. Between the end of the CD-I data and any CD-DA tracks, there must be a further 2250 or more message sectors.

Message sectors are intended to protect existing CD-DA players when they play CD-I discs containing data which might otherwise harm the CD-DA player or associated audio system.

Disc Label

The disc label is recorded in Mode 2, Form 1 - that is, with extra error protection - and contains a description of all the files on the disc, its contents, size, creator and so forth, as well as the location of any software modules which must be loaded into the system, and the path table which allows access to those files.

The disc label must, of course, be in Track 1 at the position shown in the diagram above.

The disc label comprises three records: the File Structure Volume Descriptor, the Boot Record and the Terminator Record.

Chapter 7: How CD-I works 111

Path Table and Directories

Parent Directory Number 1

Relative Directory Position File Name Root CMDS Games Library Checkers Chess Globono Frank Gibson Text Video

“-“AOOANONAHKWN—

—_— —t oOoOnoshsPWWWOH H+

A path table must be recorded on each disc. This provides an index of the Directory Structure on disc typically following the disc label. Its location on disc is given by the disc label. This is illustrated by the example shown in the figures. The path table comprises a list of all the directories.

Directory Structure

112 CD-l: A Designer's Overview

® Directory Name Each Directory is a file containing file descriptor records.

Files

All data on a CD-I disc are divided into files. Any file may be accessed through the path table recorded on the disc. Each file is represented by a File Descriptor Record contained in the appropriate Directory file which contains the file name, number, size, address, owner, attributes, interleave and the access permissions for read. Files may, in fact, be interleaved on the disc so that itis not necessary for one file to end before the new file begins.

There are several types of file: directory files, real-time files and standard files.

CD-I SECTORS

CD-I data are divided into discrete units called sectors. These sectors are similar (but not identical) to those specified for CD-ROM. In the case of CD-I, these sectors contain as well as either audio, video or computer data, the vital information which the system needs to handle this data efficiently in real-time. (One CD-I sector is equivalent to one frame of CD-DA.) CD-I data are recorded and transmitted at a rate of 75 sectors per second.

CD-I Sector Format

Each CD-I sector has a total length of 2352 bytes, and apart from synchronization information, also contains a header and sub-header, followed by data. The header provides information on the sector address in minutes, seconds and sectors relative, to the start of the track. It also indicates the Mode - which in the case of CD-I, is always 2. The sub-header comprises the following: the data type (that is, audio, video or program-related data), the form (which may be 1 or 2), trigger bits (including end of record and end of file) and the coding information (the format of which depends on the data type).

Form 1 sectors contain 2048 bytes of user data and an additional 280 bytes of error detection and correction code, and are intended for data whose integrity is essential, such as application programs, other control data and text, where there is no built in redundancy to allow for errors.

Chapter 7: How CD-I works 113

Form 2 sectors contain fully 2324 bytes of user data, but no extra error correction, and so are more suitable for less sensitive data such as audio and video. Where the presence of errors will not seriously affect the operation of the player, Form 2 sectors still allow errors to be detected so allowing error concealment techniques to be used.

'++——— TOTAL 2352 BYTES———»

r] Form 1

Form 2

For example for video data a line or pixel in error may be replaced by the adjacent line or pixel.

CD-I Audio Sectors

<«—____— Sector Data ——————_»

20B \\Spare

Audio Sector

114 CD-I: A Designer's Overview

In CD-I, audio data is held in Form 2 real-time sectors. The sub-header contains information on the emphasis, the number of bits per sample (that is, either 4 bits for levels B and C, or 8 bits for level A) and the sampling rate (which is either 37.8 kHz for Levels A and B, or 18.9 kHz for Level C). Finally, the coding information indicates whether the sector contains mono or stereo sound.

The data in each sector comprises 2304 bytes plus a spare 20 bytes, and is divided into 18 sound groups of 128 bytes each. Each sound group is further subdivided into 16 bytes representing the sound parameters and 112 bytes of actual sound data. The audio data include range and filter parameters, which are optimized in the encoding process for each sound group.

Relative Sector Number

ra Sco Lents SU obx ofitobstofsdofxto belo

LovelB S rloloblolabltotobetolol

: pieiobetteblolo Pope teveic s [1000000] 0|x10] 0] o[0Jo]o]o]x| “ Pdetoetetetsietietetetle tole

[~~] Audio Sector

The audio sectors are interleaved as shown in the figure. For real-time audio, Level A stereo sectors are in alternate sector numbers (that is, in the relative sector numbers 0, 2, 4, 6 ...) while at the other end of the range, Level C mono sectors are encoded only in every sixteenth sector.

CD-I Video Sectors

CD-I Video data are also contained in real-time Form 2 sectors. The coding information for video sectors comprises:

® the resolution (that is normal, double or high); ® the coding method (DYUV, CLUT, etc.);

® an even/odd lines flag, which is used for error concealment. The video data is transferred directly to memory and decoded in the video processor. Visual images are coded on disc as described below.

Chapter 7: How CD-Il works 115

DYUV Images

4 bits 4 bits 4 bits

Each pixel pair is represented by 2 bytes (16 bits) organized as shown in the diagram. DY, DU, DV are the differential (or delta) values of luminance and color difference. Each 4-bit value is converted to an 8-bit value (representing 0 to 255) which is added to the previous value in the decoder. In calculating these delta values, the encoding process must take into account quantization errors to avoid the effect of cumulative errors. Also, since negative values are achieved by ’wrap around’, the encoder must avoid a pixel pair.

CLUT Images

8-bit CLUT

7-bit CLUT

4-bit CLUT

116 CD-I: A Designer's Overview

There are a number of different CLUT modes. CLUT-8 uses 8 bits of information to define the full pallette of 256 colors.

CLUT-7 or 7-bit CLUT provides 128 colors, also at normal resolution. For double resolution, CLUT-4 or 4-bit CLUT provides only 16 colors but allows twice as many pixels horizontally as normal resolution, which can be valuable for text screens particularly in complex character sets such as Japanese where details become more visible in double resolution.

CLUT images are coded with 1 byte per pixel (normal resolution) or 1 byte per pixel pair (double resolution) as shown in the diagram.

RGB 5:5:5 Images

Upper Bank=

1bit 5bits 2 bits

Lower Bank= |

T=Transparency bit

The two banks are coded separately.

Run-Length Images

In normal resolution, 2 bytes of data are used to define first the color (taken from the pre-selected CLUT table) and then the number of pixels which will appear in that color before the next color change - that is, the number of pixels for which the color will be retained. In double resolution, pixel pairs are defined together.

Run-length images are coded as 7-bit (normal) or 3-bit (double).

Chapter 7: How CD-I works 117

7-bit Run_Length

3-bit Run_Length

Pixel Pair 3-bit Run of Pixel Pairs

Program-Related Data Sectors

Program-related data sectors are always Form 1, since they needa higher level of protection than simple audio and video data. Computer data in CD-I may comprise application programs, control data, text or character fonts, in real-time or non-real-time, depending on the application.

Real-time sectors generally contain control data and synchronization information which is associated with audio and/or video sectors.

CD-I DECODER

CD-I decoders must be designed so that all discs can be played on all decoders. This implies that each decoder must be designed to meet one specification and certain parts of the decoder will be common to all.

118 CD-I: A Designer's Overview

The CD-I specification defines a base case decoder - that is, the minimum configuration which can be called a CD-I decoder. The figure contains a block diagram of such a decoder. It comprises:

¢ A compact disc player, plus CD-DA decoder and controller. (These may be identical to those found in current CD-players.)

The audio processor, including ADPCM decoder and audio proces- sing unit and attenuators.

The compact disc control unit needed to provide the random access for CD-I and to provide real-time decoding of the sector information.

The microprocessor. The DMA controller.

The video processor and access controller.

The Random Access Memory Non volatile RAM.

The clock and calendar.

The X-Y pointing device.

The optional keyboard.

The Read Only memory