DDP (Disc Description Protocol) is a protocol that was created in the late ’80s by Boon Kelly and Doug Carson that is used for the final delivery of masters to CD manufacturers/duplicators. The DDP files consist of standard-format metadata that describes the data that will be duplicated on CD, sort of like a cue sheet for the CD. Information includes the name of the track file, artist name, track and index number, start and play time, ISRC, and other information. A DDP image holds the project’s audio information as a single stereo audio file.
One advantage to using DDP files for submitting masters to duplication is that DDP is delivered using CD-ROMs instead of audio CDs; CD-ROMs have better error correction than audio CDs, so the data is more robust.