Specifications

CD-i FAQ 2000 Edition Revised February 21, 2001

Latest version and more CD-i info: http://www.icdia.org

complex programs, additional audio samples, or faster transition of pictures that are stored in

RAM and need not to be loaded from the disc again.

The additional 1 MB of RAM in the Digital Video cartridge is not defined in the Green Book, nor in

the Digital Video extension, but since it is a standard part of every Digital Video equiped CD-i

player (from Philips and other manufacturers), a content developer that designs an application for

a Digital Video equiped CD-i player can be fairly sure that this extra memory is available.

3.10 What's the CSD?

Every CD-i player has a piece of non-volatile storage memory (NV-RAM) that is at least 8 KB in

size. This memory is kept when the player is turned off. Although this doesn't seem much, it

allows for powerfull storage options, such as games scores, test results, names, prefered

language settings, etc. The NV-RAM is also used by the system to store the CSD.

When a CD-i player is turned on, the CD-RTOS kernel is initialized. One of the startup routines

includes the creation of the CSD, which stands for Configuration Status Descriptor. The CSD

contains information about a certain CD-i system, such as the amount of NV-RAM available,

which kind of pointing device is connected, the version of CD-RTOS used, but also wether a

floppy disk drive is available, if a printer is connected, etc. All of these variables are stored per

device type on one line of the CSD, which are defined in the Green Book. Each of these

devicetype settings are called DSD, which stands for Device Status Descriptor (and not Direct

Stream Digital as for Super Audio-CD!). Each time the player is turned on or reset (which

happens when you eject a disc or exit from a program), the CSD is recopiled. Any newly attached

devices will therefore only be recognized and initialized after a reset.

The CSD can be read by an application program to gather information about a certain CD-i

player. For example to load a PAL or NTSC optimized version of the program, to offer storage

capabilities when a disk drive is available, to know the seek times of the CD drive, or to know the

size of the NV-RAM to show the correct usage percentages when displaying the used space of a

certain file. The CSD is stored in an ASCII file called 'csd'.

3.11 What kind of CD-drive is used in a CD-i player?

A CD-i player contains a CD-drive that runs at normal or single speed, to allow for the correct

timing when retreiving realtime data. Speeding up this drive speed would result in the requirement

of extra buffer RAM to store audio and video, which would make the CD-i player much more

complex. Furthermore, playing time of realtime data would be decreased when a disc would be

played at a higher speed.

CD-i discs are normal CDs, based on the physical definitions as laid down in the Red Book for

CD-Audio. It not a special kind of high-denisty CD, such a GD-ROM from the Sega Dreamcast,

nor does it use a differently colored reflection layer like Sony Playstation.

The CD-drive in a CD-i player is physically able to read all normal CD-types, but not high density

formats like DVD.

3.12 How does CD-i audio work?

A Base Case CD-i player should be able to decode standard PCM audio as specified for CD-

Audio, as well as a dedicated audio coding scheme called ADPCM, or Adaptive Delta Pulse Code

Modulation. The difference with PCM is that audio is not stored individually per time segment, but

that only the difference (delta) from the previous sample is recorded. This allows for a significant

decrease in the used storage space on the disc, and hence in the datastream being read from the

disc. When normal PCM CD-Audio would be used (which occupies all succesive sectors), this

would not leave room for video or animations to be read without interrupting the audio playback.