If you want to support just the ones that are hardware accelerated, then you can only support the formats that the 940 binary supports.
I've had a quick look through the code, and it seems the 940 binary supports the following formats (I'm assuming 'D' at the end means 'Decode' and 'E' means 'Encode', and so removed and placed into seperate section appropriately)
Decoders:
MP4 -
MP4_DIVX3 - These three are kinda obvious
H263 -
MJP - Motion JPEG?
WMV - Interesting! Maybe we could patch this in without licensing issues
MP1 - MPEG Audio Stream, Layer I
MP2 - MPEG-1 Audio Layer II
MP3 - MPEG-1 Audio Layer III
Encoders (not really interesting, as we have no source to encode from)
MP4
MJP
and of course, anything based on the above should work also, if you get it into the appropriate format for the decoder...
I wonder if the audio player uses the hardware mpeg decoders?