#12 Rudimentary PCM sample data compression

[yki]

There should be some kind of a simple sample data compression facility to be able to fit any song on a normal 720 kB floppy, even if it uses the whole 1024 kB of sample memory. Lossless or lossy, for example "quantized deltas", 4 bits per 8-bit sample, or ADPCM style or something.

Maybe even compress 12-bit samples packed as 8-bit ADPCM, which would be nice, because then we could better utilize the OPL4's 12-bit PCM capability.