Specifications
CD-i FAQ 2000 Edition Revised February 21, 2001
Latest version and more CD-i info: http://www.icdia.org
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3.7 What's CD-i's disc structure?
Like with all official CD-standards, a CD-i disc is devided into tracks. A CD-i disc contains at least
one CD-i track, and my optionally contain additional CD-Audio tracks that may also be played on
a standard CD-Audio player. The CD-i track must be the first track on the disc, with the optional
CD-Audio tracks hereafter. An exception to this rule is defined in the 'CD-i Ready' format, which is
covered in more detail in section 5 (Disc types).
The first 166 sectors of the CD-i track are message sectors, followed by the Disc Label. Hereafter
come an additional 2250 message sectors. Message sectors contain a spoken message in CD-
Audio format, which informs users who put the disc in a regular CD-Audio player about the
possible damage to equipment or speakers when the disc is not taken out immediately. Usually, a
modern CD-Audio player will recognize the CD-i track as a data track and will not play it, so you
won't hear the message. It's only included for compatibility with older CD-Audio players. The Disc
Label contains some specified fields which offer a lot of information about the disc, such as the
title, creator, experiation date, but also the name of the CD-i application file that needs to be run
at startup. Most of those fields are not used by most CD-i players, but it allows for example for
CD-i players which show the name of a disc on the FTD-display or in the player shell.
Furthermore, the Disc Label contains the File Structure Volume Descriptor, which is loaded into
RAM at startup. This allows the system to find a certain file on a CD-i disc in only one stroke.
After these message sectors and Disc Label, the actual CD-i data starts.
3.8 What filesystem does CD-i use? Is it based on ISO-9660?
A true CD-i disc uses the OS-9 filesystem, which is not compatible with ISO-9660. It allows for
additional information about the files to be stored. This information is very Unix-like, and contains
data about execution or read permissions. The filenames can be up to 28 characters in lenght.
The system also provides for unlimited depth subdirectories to be used on the disc. Files can
contain upper and lower case characters, but files may not exist with excisting names in upper
and lower case (for example: when a file 'multimedia' is present, the file 'Multimedia' may not
exist).
Since CD-i uses a dedicated filesystem, it is not possible to see the filenames on a disc using a
regular computer with a CD-ROM drive. However, a CD-i filesystem driver has been written for
Windows 95/98, that allows you to access a CD-i disc in the same way as a CD-ROM. More
information about this driver can be found in section 9 of this FAQ: CD-i on other platforms.
Altough a CD-i disc is not ISO-9660, the Green Book defines that a CD-i player must be able to
read ISO-9660 discs, for example data from a CD-ROM disc. It is also possible to include a CD-i
application on a standard ISO-9660 CD-ROM disc to enable playback on a CD-i player. This is
defined in the CD-i Bridge format, as explained in further detail in section 5 of this FAQ: Disc
types.
3.9 How much RAM does CD-i incorporate?
The Green Book defines that a CD-i player should at least have 1 MB of Random Access
Memory. This memory is devided into two memory banks of 512 KB each. Each of these banks
contain one video image of CD-i's two video planes (see: 3.13 How does CD-i video work?)
Depending on the video encoding type, a picture takes up about 100 KB, leaving the remaining
memory for application programs, data, sound samples, and all other kinds of information.
All consumer CD-i players contain 1 MB of RAM by default, but when a Digital Video cartridge is
installed, additional memory is added. Besides the 512 KB of decoding RAM, the cartridge also
offers a full 1 MB of extra memory. When no Digital Video is displayed, the decoding RAM can
also be used for general purposes. This makes up for a total of 2,5 MB RAM in a CD-i player
equiped with a Digital Video cartridge, allowing content developers to use more RAM for more