As a separate extension to the Yellow Book introduced in 1988 by Philips, Sony and Microsoft, the CD-ROM XA specification comprises the following:

  • Disc format including Q channel and sector structure using Mode 2 sectors
  • Data retrieval structure based on ISO 9660 including file interleaving which is not available for Mode 1 data
  • Audio encoding using ADPCM levels B and C
  • Video image encoding (i.e. stills)

While the original CD-ROM format is known as Mode 1, and CD-ROM XA is known as Mode 2. It is generally consider with the ISO 9660 logical format but designed to add better audio and video capabilities so that CD-ROM could more easily be used for multimedia applications. CD-ROM XA was abandoned as an independent multimedia format, but the physical format was used in the CD-I Bridge formats Photo CD and VideoCD plus Sony’s Playstation.