KB19: CD-ROM/XA - Modes and Forms

When burning CDs - this does not apply to DVDs - there are two modes which are used for burning:

Data is written with error correction. Used for burning data discs. 2048-byte sectors.
Data is written without error correction. Used for burning audio discs. 2336-byte sectors.

This has two consequences: Since Mode-2 does not need any disc space for error correction information, it allows you to store more data.

Example: If you have uncompressed audio tracks (WAV files) which have a size of 800MiB in total (approx. 80 minutes), you can burn them as audio disc, but not as data disc. If these 800MB would have to be burned to disc plus error correction information, there would not be enough space on a typical CD-R. So you can burn 807,5MiB of audio data (without error correction) to an 80min/700MB CD-R, but only 703.1MiB data as data disc.

Since Mode-2 does not have any error correction, it also is not possible to verify a burned audio disc. For a reading device, there is no way to find out whether or not data has been read correctly from a disc. It cannot be guaranteed, that an audio disc you burn is free of errors. Since it contains only audio data though, minor errors are usually not noticable (which would be a problem for data, like executable applications).

Additionally to those modes, there also is CD-ROM/XA (eXtended Architecture). This is written as Mode-2, and may be Form-1 (error correction) or Form-2 (no error correction). This option has been created for CD-i, which is not widely used.

Further reading