CD sector contents

• A standard 74 min. CD contains 333,000 blocks or sectors.
• Each sector is 2,352 bytes, and contains 2,048 bytes of PC (mode 1) data, 2,336 bytes of PSX/VCD (mode 2) data, or 2,352 bytes of audio.
• The difference between sector size and data content are the header information and the error-correcting codes, that are big for data (high precision required), small for VCD (standard for video) and none for audio.
• If extracting the disc in raw format (standard for creating images) always extract 2,352 bytes per sector, not 2,048/2,336/2,352 bytes depending on data type (basically, extracting the whole sector). This fact has two main consequences:
  • Recording data CDs at very high speed (40×) can be done without losing information. However, as audio CDs do not contain a third layer of error-correcting codes, recording these at high speed may result in more unrecoverable errors or 'clicks' in the audio.
  • On a 74 minute CD, one can fit larger images using raw mode, up to 333,000 × 2,352 = 783,216,000 bytes (~747 MiB). This is the upper limit for raw images created on a 74 min or ~650 MiB Red Book CD. The 14.8% increase is due to the discarding of error correction data