[Koying]

My (small) research contribution:

Thanks for your research.

VC-1
libwvm is a proprietary codec by Widevine, which is a Google company. Here is their webpage and contact information: http://www.widevine.com/contact.html
I think you're unlikely to get any source code, but hopefully they will answer a technical question.

Also, Cyanogen distributions ship with libwvm, so would it not be possible to use it for XBMC as well (if needed)?

They probably handle DRM as well. We cannot use it as such, because we have our own demuxer.

MP4 - Tegra3
Is it possible to turn on all available cores and only do software decoding (until the hardware decode works)?
Can you say what's causing the issue -- so maybe we could help track down a solution?

Actually, MP4 decoding works very fine in SW on tegra3. It's just for the sake of completeness.
It just says "coding method not supported" or equivalent. Not much hope on the decoding side, but it would be good to be able to differentiate the problematic ones to increase granularity.