A DDP image (Disc Description Protocol image), also known as a DDPi, is a set of files used when replicating a CD or DVD. That set of files contains all of the data necessary to create a CD or DVD. In other words, whatever information your end user can see or hear when they pop a CD in for playback is contained in the DDP image (note: their CD does not contain the DDP image itself, but instead contains the data in a usable format). Pictures, audio, track titles, the order of tracks, etc. are all included.
Once a DDPi has been prepared, it is sent to a replication facility where a master copy is made, and the project is then replicated onto CD or DVD.
Why is DDP the preferred master upload format?
The DDP image is the industry standard and is preferred for several reasons:
1) It can be delivered electronically—much faster than mailing or delivering a CD/DVD in person.
2) A DDPi is more likely to produce CDs or DVDs with consistent results. If you were to burn a copy of your CD (identical to the end result) and send it to be replicated, physical defects would cause variations in your end result.
3) DDP images can be checked for accuracy to make sure the data received by your facility is an exact match of what you created. This option is not available for CDs or DVDs.
So why not create a DDPi and burn it onto a CD/DVD?
Electronic delivery of your DDPi reduces the likelihood that your facility will accidentally burn copies of the DDPi. A CD with your DDP file on it is not the master—it is used to create the master. The confusion comes when a facility employee mistakes your CD with the DDP file for the master itself and makes copies. You don’t want exact copies of your DDP image because your end user wouldn’t see or hear anything when using one of those copies in their computer or CD/DVD player. The DDP image CONTAINS all the data that will ultimately go on your CD or DVD, but not in the format your average user can access.