compact disc read only memory extended architecture (CD-ROM/XA)
The CD-ROM/XA is based on the well-known CD-ROM and extends the CD-ROM specifications with regard to simultaneously usable files, such as audio and computer data stored in interleaved form, interleaving. The CD-ROM/XA format allows the simultaneous use of different types of information. This format is also called Mode 2 format.
There are XA-type format versions for audio and video, and for two data formats. Both data formats correspond to each other in the synchronization (12 bytes) and in the header with 4 bytes of address information. However, they differ in the 8- byte subheaders.
The subheader contains the submode information and an encoding information. The sub- mode ensures the assignment of a file to the corresponding channel; the encoding information activates different audio quality levels. The data format of the CD-ROM/XA is logically identical to the CD-ROM format. It contains after the 2 KB long data set the 4 bytes for error detection and the 276 bytes for error correction.
Compressed audio data is transmitted in the sub-mode 1 format, and four different audio classes can be set in the coding information byte. These classes differ in terms of quality and playing time.
Class A corresponds to audio CD quality with 44.1 kHzsampling rate and a bandwidth of 20 kHz. Class B offers good music quality with 17 kHz bandwidth at a sampling rate of 37.8 kHz, with a playing time of 592 minutes in mono mode and 296 minutes in stereo. Class C has voice quality with a bandwidth of 8.5 kHz. The playing time is doubled compared to class B.
In terms of data storage, 75 sectors with 2,304 bytes each are available per second, which amounts to 172,800 bytes of information per second.