Archive for June, 2006

VC-1: Some more progress

Friday, June 16th, 2006

Yesterday I’ve rewritten decoder using FFmpeg’s functions from h263 decoding. Now the code is simplier and decodes more I-frames correctly but the problem with AC prediction remains.
Here is the output of new decoder, the same scene:
Decoded frame from second version of decoder

VC-1: Something is showing up

Thursday, June 15th, 2006

Yesterday I’ve managed to beat more or less sane I-frame decoder.
It is not very good now but at least it works and produce something that could be recognized without lots of imagination:

One of decoded frames

VC-1: Middle layer problems

Wednesday, June 14th, 2006

Yesterday I’ve managed to hack FFmpeg bits of VC-1 decoder to actually parse and decode simple profile I-frames. Bits consumed are fine. But there is no sane picture yet. DC prediction is not good and AC coefficients also needs some operations, but at least they are decoded correctly.

VC-1: 8×8 transform

Saturday, June 3rd, 2006

OK, 8×8 transform is slightly optimized too.

This version gives 7x gain on PII and 15x on G4.

Here is vc1itrans.c file from VC-1 reference decoder with replaced transform.

See here
how to use VC-1 reference decoder in FFmpeg
and just replace one file in libvc1 with my version before compiling.

VC-1: 4×4 transform

Saturday, June 3rd, 2006

I was honoured to implement VC-1 decoder in course of Google Summer of Code.

I had almost no time to do anything this week but at least here is straightforward optimization of 4×4 transform.
Speed gain varies from 4 times (PII-266) to 7 times (PPC G4-1.42 GHz). My name is not Niedermayer and I’m not sure how to further optimize it / rewrite with MMX/AltiVec but it’s a good start. 8×8 transform will follow soon (I hope).

The test code is given below.