CD-XA Disc Formats
The CD-XA media driver provides access to devices that support CD-ROM/XA discs. CD-XA (Compact Disc-Extended Architecture) refers to a storage format that accommodates interleaved storage of audio, video and standard file system data. CD-XA data is stored in a file system format on the discs, and playback control is managed by the CD-XA media device in cooperation with the amplifier-mixer device.
CD-XA takes advantage of a special ADPCM audio compression mechanism that not only yields a low data rate but also enables more audio data to be stored on a disc than that allowed by a CD-DA disc. ADPCM (Adaptive Delta Pulse Code Modulation) is an audio compression technique that allows up to a 16 to 1 compression of audio data.
By compressing the audio data (in some cases to 1/16 the size of CD-DA data) it now becomes possible to record multiple audio tracks on a single disc. With CD-XA level C, recorded in stereo, it is possible to interleave 8 different audio tracks on a single disc. With CD-XA level C, recorded in mono, this number climbs to 16 different tracks on a single disc.
The following table summarizes the different compression levels available with CD-XA and compares them to CD-DA.
┌──────────┬───────────┬──────────┬─────┬──────────┬───────────────┬──────────┐ │Type │Audio │Video │File │Data Rate │One Sec of │Spec │ │ │ │ │Sys │per Sec │Audio Data │ │ ├──────────┼───────────┼──────────┼─────┼──────────┼───────────────┼──────────┤ │CD-DA │16-bit PCM │No │No │172KB │Stereo: 172KB │Red Book │ │ │at 44.1 kHz│ │ │ │ │ │ ├──────────┼───────────┼──────────┼─────┼──────────┼───────────────┼──────────┤ │CD-DA+G │16-bit PCM │288 x 192 │No │172KB │Stereo: 172KB │Red Book │ │ │at 44.1 kHz│CLUT4 │ │ │ │ │ ├──────────┼───────────┼──────────┼─────┼──────────┼───────────────┼──────────┤ │CD-ROM │No │No │Yes │150KB │N/A │High │ │ │ │ │ │ │ │Sierra, │ │ │ │ │ │ │ │ISO 9660, │ │ │ │ │ │ │ │Yellow │ │ │ │ │ │ │ │Book │ ├──────────┼───────────┼──────────┼─────┼──────────┼───────────────┼──────────┤ │CD-XA │4-bit ADPCM│320 x 200 │Yes │150KB │Mono: 18.75KB │Green Book│ │Level B │at 37.8 kHz│640 x 480 │ │ │Stereo: 37.5KB │ │ │ │ │CLUT1, │ │ │ │ │ │ │ │4 or 8 │ │ │ │ │ ├──────────┼───────────┼──────────┼─────┼──────────┼───────────────┼──────────┤ │CD-XA │4-bit ADPCM│320 x 200 │Yes │150KB │Mono: 9.4KB │Green Book│ │Level C │at 18.9 kHz│640 x 480 │ │ │Stereo: 18.75KB│ │ │ │ │CLUT1, │ │ │ │ │ │ │ │4 or 8 │ │ │ │ │ └──────────┴───────────┴──────────┴─────┴──────────┴───────────────┴──────────┘