Now that I'm getting the hang of IDA here is another crappy codec I added: Konami XMD (Xbox)
This also seems inspired by XA/PS-ADPCM, only one filter but resets ADPCM output every few samples (potentially better sound?). Guess somebody was bored, since Xbox had a bunch of standard codecs.
I didn't have IDA Pro at hand to decompile the .xbe so it's based on xmddecode.dll from some russian Silent Hill tools.