The CD-Bridge Disc specification defines a way to put additional information in a CD-ROM / XA track in order to allow the track to be played on a CD-I player. The result is a disc that can be played on both a CD-I player connected to a TV set and on a CD-ROM / XA player connected to a computer. Bridge Discs may also be played on other XA compatible devices (KARAOKE player, Photo CD player, 3DO, etc.) if the data contains the necessary application software.
An example of the above is the Photo-CD disc (Bridge Disc) described on Page 23. The Photo-CD disc is playable on CD-I players, computers using a CD-ROM / XA drive or driver, and on Kodak Photo CD Players.
It should be noted that being able to play a Bridge Disc on an application specific device does not necessarily mean that you can play all types of Bridge Discs on this device. For example a Photo CD player can play Photo CD's which are Bridge Discs. However, a Photo CD player can not play KARAOKE CD's which are also Bridge Discs. Both of these types of discs are Bridge Discs by definition. They just can't be played on each others application specific device.
A CD-Bridge Disc must conform to all the requirements of both the CD-I and CD-ROM / XA specifications.
Technical Information about the CD-Bridge Disc:
The CD-I and CD-ROM / XA standards define volume descriptors that point to where the directory structure starts. The volume descriptors for CD-I and CD-ROM / XA are different and both need to be included on a CD-Bridge disc. The CD-I standard (Green Book) specifies a volume descriptor located at ATime 00 minutes, 02 seconds, 16 frames, and 0 byte offset. The CD-ROM / XA standard specifies a volume descriptor located at ATime 00 minutes, 02 seconds, 16 frames and a 1024 byte offset. Because of the offset, both volume descriptors can be written in the sector (at 00 minutes, 02 seconds, 16 frames) and not interfere with each other.
On a CD-I disc (not a Bridge disc) the CD-I track is NOT included in the disc Table of Contents (TOC). This was done to protect some audio players from playing the CD-I data as audio and possibly damaging the speakers. The Bridge Disc track is included in the TOC and is listed as a CD-ROM / XA track. This was done so that XA drives as well as CD-I players can access the data.
The sector layouts for the CD-Bridge disc are identical to CD-ROM / XA and CD/I.
Sector Layout for CD-I, CD-ROM / XA, and CD-Bridge Discs:
