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Compact Disc Digital Audio

May 11, 2010

To make it simple, an audio CD (Compact Disc Digital Audio) is one that you buy from stores and contains only audio tracks. Audio CDs are compatible with most of current CD-drives, including your CD/DVD drive on your computer, and your car CD player. For little more details, this standard of Audio CDs is called the “Red Book“, which was first released in 1980 by Philips and Sony.

The audio tracks are uncompressed digital data (essentially WAV). This explains why you can’t fit 100 songs in an audio CD like an MP3 CD because the size of each track is big. Try to plug an audio CD into your computer CD/DVD drive, what you’d see are some files with the names similar to “track01.cda”. These are audio tracks, and you can’t just open them with your computer like any other computer file. A CDA file simply points to the location of the audio track on the CD. Also, you cannot copy these CDA files to another location with your computer. Why? because they contain no audio data, they are just the “pointer” files. The actual audio data is stored on the CD sectors and cannot be viewable on your computers.

An audio CD normally can hold up to 74 or 80 minutes of audio. So when you create an audio CD from some MP3 files, no matter how big or small your mp3 files are, the CD can only fit in up to 80 minutes of audio.

  • Pro: Compatibility. Audio CDs can be played on most CD players/drives.
  • Contra: Size limit. You can’t fit many songs into an audio CD.

Audio Spec

  • The frequency response: from 20 Hz to 20 kHz.
  • Bit rate = 44100 samples/s × 16 bit/sample × 2 channels = 1411.2 kbit/s (more than 10 MB per minute)
  • Sample values: range from -32768 to +32767.
  • On the disc, the data are stored in sectors of 2352 bytes each, read at 75 sectors/s.

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