Nearly everything. We support hundreds of codecs and formats, including all of the most common ones.
It’s actually probably more helpful to talk about the formats we don’t support, since that’s a manageable list. At the moment, there are only a few:
ER AAC LD (Error Resiliant, Low-Delay variant of AAC)
Avid Meridien Uncompressed
REDCODE Video File (.r3d)
Other than these codecs, which we hope to support soon, we can handle just about anything.