On Wednesday 04 May 2005 02:03, Timothy Miller wrote: > Ummm... anyone want to tell me the math that goes into the last MPEG > decoding stage just before YUV to RGB conversion? :)
That's motion compensation it seems, and the step before that is the iDCT. The article at http://www.cs.princeton.edu/research/techreps/TR-516-96 has an overview of MPEG-2 decoding in its introduction. There are probably better references, but it seems that the last step before conversion essentially takes a bunch of frames, and a set of motion vectors and error data, and then pieces a frame together by copying blocks from the source frames, shifting them according to the motion vector, adding the error data, and pasting them into the target frame. In practice, I suppose we'd have to support the XvMC extension to be able to claim hardware accelerated MPEG playback (http://www.xfree86.org/~mvojkovi/XvMC_API.txt). Lourens
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