I've been reversing LeapFrog handhelds for about 3 years now. The one thing I've always been insanely curious about is how the compressed voice codec on them works (all of their devices from 2008 and earlier minus the Didj used the same codec). I have tons of the source WAV files they converted into this format, but the format itself still confuses me. If anyone would like to look into them, here's a zip with a ton of sample files (alongside their sources):
Batman voices.zip

Edited August 19, 20241 yr by Blingus

Some small bits of info I've figured out on my own just from looking through them:
The first two bytes appear to be the compression level.
The second two bytes are unknown, but appear to be part of the header too
There's tons of instances of FF 0F in the data. Most of the files have C0 0F near where they end.

Just a shot in the dark here, but could LPC stand for linear predictive coding? That would make sense since LPC seems to mostly be a speech coding thing.

Yes, the compression format was primarily used for voices. Sound effects were done occasionally, but mostly for stuff that compressed well or when the cartridge didn't have any more space for A-Law audio data.