CD-i FAQ 2020 | Back to Index
Section 1. The CD-i system
1.1 What is CD-i?
CD-i is short for Compact Disc Interactive. It is an interactive multimedia system combining moving and still video, audio and program content on a compact disc, which can be played back in a dedicated CD-i player. A CD-i player is a stand-alone device, consisting of a CPU, memory and an integrated operating system. It operates on its own and it can be connected to a standard TV-set for displaying pictures and sound, and optionally to a stereo-system. All system interactivity is generated by positioning a cursor using an X/Y pointing device (such as a remote control with a pointing device or a mouse), and clicking options using one of the two provided action buttons.
1.1.1 When was CD-i launched and discontinued?
The first CD-i players for professional use (and for the authoring of CD-i titles) were introduced in 1989, with some earlier pre-production versions becoming available from 1988 onwards.
The first CD-i players for consumers where launched in October 1991 in the US, and a year later in Europe and the rest of the world. CD-i players were sold on the consumer market until 1997.
For professional applications, CD-i players were manufactured until June 1999. That month, the latest batch of CDI 660 and CDI 670 players were manufactured in the Philips factories in Hasselt, Belgium.
1.2 Who created CD-i?
CD-i was jointly developed by Philips Electronics NV and Sony Corporation in the mid 80s. Together, both companies defined CD-i's basic specifications in what is known as the Green Book. They decided to use the well-tested OS-9 operating system from Microware Systems Corporation, which was designed for embedded, real-time applications. Microware was also heavily involved in the CD-i design process. Eventually, Philips took the biggest part in the development process, being responsible for at least 90% of CD-i's development.
1.3 Is CD-i propietary?
Developers of CD-i software do not need a license, from a software point-of-view, CD-i is an open standard. Of course, as with all CD-types, the normal CD-pressing license fees need to be paid, but this is to be taken care of by the CD pressing plant. Manufacturers of CD-i (compatible) players need a license from Philips and Microware.
1.4 What is the Green Book?
Green Book is the informal name of the Compact Disc Interactive Full Functional Specification, as laid down by Philips, Sony and Microware. It is named after the green cover of the book, and it is in line with the other CD-systems which also bear their own "color"-identification (such as red for CD-Audio, yellow for CD-ROM and white for Video-CD). It is sometimes also referred to as FFGB or Full Functional Green Book. The Green Book consists of the CD-i specification and the Microware OS-9 2.4 Technical Manual. In contrast to other CD-systems such as CD-Audio and Video-CD, the Green Book not only specifies the disc-format of the system, but also the playback-device including the required CPU and operating system are specified in detail.
1.5 What versions of the Green Book are available?
In essence, there is only one Green Book. However, some minor additions, changes and fixes have been applied over the years (as is the case with the original CD-Audio specification!). When we do not count early "pre-release" versions, the first version of the Green Book is dated September 1990. The first major revision is the March 1993 edition, which included Chapter 9 (the CD-i Full Motion Video extension). The latest version dates back to May 1994.
Note: As of July 24, 2017, Changes documents that detail these revisions are available in the CD-i Full Functional Specification (Green Book) section of this site.
1.6 Where can I get a copy of the Green Book?
The Green Book is no longer available in print but since at least August 2011 it has been freely available online as a PDF document. Before that, it was available as a digital file on CD-ROM at a price of US$ 150. Licences and copies of the Green Book were available from Philips System Standards and Licensing. As a hardware or software developer, you could subscribe to receive all Philips CD standards including updates for a period of 5 years for US$ 5000.
Note: As of July 24, 2017, the March 1994 revision of the Green Book is digitally available in the CD-i Full Functional Specification (Green Book) section of this site.
1.7 Will any CD-i disc play on any CD-i player?
In general: yes. This is one of the beauties of the CD-i system. Since both disc and playback devices are extensively specified, every CD-i disc is compatible with every CD-i player, in contrast to a CD-ROM disc, of which you never know whether it will play on your PC-configuration. Look for the CD-i logo on both disc and player to ensure compatibility. Please note that it is possible for both software and hardware manufacturers to include additional features which are not part of the basic CD-i specification. Discs which are designed for these extensions (such as a Digital Video cartridge, keyboards or modems) will play on standard CD-i players, however they will lack the additional functionality. At least, they must display a message indicating that additional hardware is required to play the disc.
Apart from the Digital Video extension (and if you want to count the modem that was part of the CD-Online CD-i/Internet kit and the KeyControl external keyboard), in practice there were no additional extensions available for regular consumer CD-i players. Various extensions were available for professional/authoring CD-i players, mostly used for CD-i development (see section 7).
1.8 What's a Base Case player and a Base Case disc?
Every CD-i disc or CD-i player which conforms to the minimal demands as set by the Green Book is called Base Case. This means that a Base Case title plays on every CD-i player, and that a Base Case player will play only Base Case discs. When a title uses an extension to the standard specification, such as implementing Digital Video, it is no longer considered a Base Case title, since it is not ensured that this disc will play on all players. It must however be able to start up and display a message indicating the required extension.
1.9 Does CD-i support Full Screen video?
The basic CD-i specification allows a CD-i player to display full screen animations in 128 colors over a 16.7 million color background, or play partial screen moving video in a lower framerate in 16.7 million colors, both with accompanying sound. However, these capabilities are extended when a Digital Video cartridge is placed in the player. In this case, the player is able to display full-screen, full moving 30 fps video in 16.7 million colors in up to 384x280 (non-interlaced only) resolution, according to the MPEG-1 standard. Although Digital Video is not a part of CD-i's basic specification, it is generally considered to be a "must-have" extension to a CD-i player since it adds an enormous audiovisual performance boost to the system. Digital Video is specified as an optional extension in chapter 9 of the Green Book.
1.10 What disc types can be played on a CD-i player?
In general, a CD-i player only plays discs that incorporate a dedicated application program that was designed for CD-i's operating system and hardware components. For some disc types, such as Video-CDs, Photo-CDs and CD-BGM, this CD-i application is a mandatory part of the disc's specification. This means that in order for a Video-CD to bear the Video-CD logo, it must contain a CD-i application, and it must be able to be played back on a CD-i player. Next to this, the CD-i standard requires the player to be able to play back standard CD-Audio discs. Most players (including all Philips consumer models) are able to display the graphic contents of CD+Graphics discs, although this is not a requirement of the CD-i standard.
In conclusion, a CD-i player plays CD-Audio, CD-i, CD-BGM, CD-ROM/XA Bridge discs like Photo-CD and Video-CD, and most of them play CD+Graphics as well. Please refer to the Disc Types section in chapter 5 of this FAQ for more information on the various CD systems that can or cannot be played on CD-i.
1.11 What were the advantages of CD-i over PC-based interactive systems?
CD-i had various advantages over PC-based interactive systems, of which the most important are:
1.12 How was CD-i related to other TV-based interactive systems?
In the early nineties, several other TV-based interactive playback devices using a CD as their main storage device existed. They were sold by different companies trying to pick a share of the market. Some of them were clearly based on all CD-i marketing techniques, others choose a slightly different approach.
The most important of them were:
None of these formats were interchangeable. 3DO played Photo-CDs, 3DO and CDTV/CD32 played CD+Graphics and 3DO and CD32 could be expanded with a Video-CD add-on. None of these devices managed to gain a market share comparable to CD-i, and none of them were ever used in professional applications, unlike CD-i. They all quickly disappeared from the market.
1.12.1 How does CD-i compare to DVD-Video?
Sometimes, CD-i is compared to DVD-Video. Standard DVD-Video provides some interactive features, but lacks the degree of interactivity that is offered by CD-i. The DVD-Video specification defines some limited ways of interaction (mostly based on branching to specific audio, still pictures and video content on the disc), but unlike CD-i it does not define the operating system and/or CPU architecture, and hence does not allow for more complex interactive programs.
Philips sold a professional DVD-Video player (DVD170) which added the capability to be controlled by an external computer to integrate DVD-Video content with interactive programs running on that external device (comparable to how professional LaserDisc players could be controlled and superimposed by external computers prior to this).
In terms of video quality, CD-i (with the optional Digital Video Cartridge installed) is capable of up to 30 fps video in 16.7 million colors in up to 384x280 (non-interlaced only, 280p) resolution according to the MPEG-1 standard, and the system could display still images in up to full-PAL 768x560 resolution. DVD-Video can play video in full-PAL 768x560 (interlaced, 560i) resolution according to the MPEG-2 standard.
1.12.2 How does CD-i compare to Blu-ray Disc?
Blu-ray Disc builds on the DVD-Video standard by offering additional interactive capabilities and eliminating some of the limitations of DVD-Video (such as the ability to keep some audio and video in memory while doing branches on the disc, eliminating audio/video playback interruptions).
In addition to that, the Blu-ray disc specification was extended with BD-J (Blu-ray Disc Java) support in 2007, which has been a requirement for players since then. BD-J allows Blu-ray Disc players to run interactive programs based on the Java programming language, enabling features like picture in picture, saving some information in local storage and Internet-access.
Since it is based on Java’s “middleware” solution, it requires the Java code to be converted to run on a wide variety of (not specified) hardware platforms. Unlike CD-i, the BD-J system does not define the operating system and CPU architecture, and therefore has much more limited capabilities for interactive programming compared to CD-i.
In terms of video quality, CD-i (with the optional Digital Video Cartridge installed) is capable of up to 30 fps video in 16.7 million colors in up to 384x280 (non-interlaced only, 280p) resolution according to the MPEG-1 standard, and the system could display still images in up to full-PAL 768x560 resolution. The basic version of Blu-ray Disc can play video in full-HD 1920x1080 (interlaced 1080i and non-interlaced 1080p) resolution according to the MPEG-2, MPEG-4/AVC and VC-1 standards.
1.13 What is the official CD-i logo?
The official CD-i logo is the Compact Disc trademark with the word Interactive in a box in negative color beneath it. This logo may only be used on software or hardware products that comply 100% to the CD-i specification (see above: What is the Green Book?). The word Interactive may alternatively be white on a negative or positive surface. The logo may never be displayed smaller than 9 millimeters wide.
In addition to the standard CD-i logo, Philips also created a marketing logo for CD-i, which is the one you can see below. This logo may only be used by Philips, but in some cases Philips allowed other manufacturers to carry it too. It may never function as a replacement for the system logo, i.e. when it is used on hardware or software products, it must be accompanied by the system logo.
1.14 What is the correct way of writing CD-i?
Originally, Philips stated that CD-I is the correct way of referring to the system. However, since many people unfamiliar with the system pronounced this as CD-One, they changed it into CD-i (with the lower case 'i') around 1992. All other ways of writing the name (CDi, CDI, Cd-i, etc.) are wrong and should not be used.