MP3 CD

A compressed audio optical disc, MP3 CD, or MP3 CD-ROM or MP3 DVD is an optical disc (usually a CD-R, CD-RW, DVD-R or DVD-RW) that contains digital audio in the MP3 file format. Discs are written in the "Yellow Book" standard data format (used for CD-ROMs and DVD-ROMs), as opposed to the Red Book standard audio format (used for CD-DA audio CDs).

Even modern day formats such as recordable Blu-Ray discs have also come into play for this concept.

Compressed audio files are supported by many modern CD players as well as DVD players. Disc players are capable of playing compressed formats, such as MP3, the most commonly used format, as well as Ogg Vorbis, the proprietary Windows Media Audio and ATRAC.

Because of audio data compression, optical discs do not have to spin all of the time, potentially saving battery power; however, decompressing the audio takes more processor time. The audio is buffered in random-access memory, which also provides protection against skipping.

The number of files that a disc can hold depends on how the audio files are encoded and the length of the audio. A standard audio CD (74 minutes) can hold about 18 audio programs, a 650-MB data CD (equivalent to 74-minute audio CD) containing mid-quality (160-kb/s) audio files can hold approximately 9.5 hours of audio or about 138 audio tracks.

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