Moving onto sound.

I've spent the last two days digging into PCM sound for the Sega CD and Neo Geo CD.

Here's what I've found so far:

The Sega CD uses a signed bit 8 bit PCM format (7 data bits plus a sign bit). Sound Forge supports this format. The resulting PCM has to have the data aligned to even bytes (or each byte is duplicated once). The sample rate is variable.

The Neo Geo CD uses an 18500 KHZ 16 bit mono ADPCM format (similar to a Dialogic ADPCM vox format). MVS Tracker (http://www.neobitz.com/Pages/DevTools/MVSTracker.aspx) has an option to build the PCM roms for this. It can also generate the Sound (Z80) rom, but it plays to the end of a bank, rather than just a sample.

The Sound rom uses the following commands: (Using a byte written to 0x320000)
1 turns the sound off and reset the sound system.
2 plays the introduction song (the one that plays while the spinning NEOGEO letters)
3 turns the sound on and enables the processor to recieve commands.
4+ is Samples
0x7F stop ADPCM.
0x80+ are FM music tracks (at least using MVS Tracker).
0xFF Stops the FM Music.

I've added PCM sound support to the Neo Geo CD version, but still need to find a fix to play just a sample.