[MPlayer-dev-eng] [PATCH] autoq support for control()

[Juan J. Sierralta P.]

On Mon, 2002-02-11 at 00:47, Michael Niedermayer wrote:

> > 	Did you see MPEG files generated by ffmpeg on Windows Media, MTV or
> > Java Media Studio before your simple idct ? It`s the same problem when
> no, but they should show the same stripes...

	No. Acumulations error especially on chroma component. I think this
could be recreated using the other IDCT on ffmpeg, that`s why I
suggested to put your IDCT code by default. In that way we have both
DCT/IDCT of quality to avoid users saying the encoder is wrong because
the shity player they use is the hyper fast IDCT.

> > we use a bad DCT.
> no its not, the dct can be inaccurate, it might increase filesize but there 
> will be no accumulated errors
> for example the c dct had wrongly permutated scaling factors (that certainly 

	Had or has ?
	
> caused significantly more differences than the a correct aan dct) and it was

	The problem of AAN is sometimes his strength, the idea of folding
the last multiplications with the quantization can be hard to implement
and make things dificult when you have multiple DCT implementations.
That's why I said weeks ago that if we could have a common set of
IDCT/DCT in C,MMX,XMMX, etc it would be easier and maybe faster to avoid
diferent quant matrixes and coef permutation.
	BTW. Why SSE couldn't help on DCT/IDCT ? How much time is spent on MMX
DCT scaling things ? Because AFAIK one of the advantges of SSE/SSE2 is
the SIMD on floats.
 
> visible on i-frames but the problem dissapeard after a few p-frames instead 
> of getting worse and the decoder doesnt use te dct so there are no 
> differences between decoders ...

	Agree on that idea, when I put the first MMX DCT on ffmpeg I take some
that weren't accurate and gave me acumulations errors. This is going to
an holy war. Just to make clear, let`s review on Arpi's TODO I agree
with him that maybe the bitstream writer could be optimized first. Then
I think the MB skip could give good results.


-- 
Juanjo sin .sig :(