ProPacker 2.1

General Information
A module packer created by Christian Estrup.

Technical Information

 * File Prefix/Extension
 * pp21

File format
Overall, a standard Protracker song is broken down from a standard 1024 byte pattern (4 channels * 64 notes * 4 bytes per note) into 4 patterns, one per audio channel. If any such one-channel pattern appears more than once in the song (e.g. repetitive drum patterns), it can now be de-duplicated. The size of the song can increase at this point, because instead of having one position list for all 4 channels (128 bytes), there are now 4 independent lists (128 * 4 = 512 bytes).

The next step is to take all notes in all patterns and build a unique list of notes. For example, the " --- 00000 " note ("no note") is very common. Assuming there are less than 65536 unique notes in the music, every note can be converted to a 16-bit index into a table of the 4-byte notes.