[XviD-devel] [In progress] devapi4 -- mpeg matrices
skal
skal at planet-d.net
Fri Nov 28 10:22:30 CET 2003
Hi GomGom and all,
On Fri, 2003-11-28 at 10:41, Edouard Gomez wrote:
> skal (skal at planet-d.net) wrote:
> > Sure, no pb. But beware:
> >
> > a) i'm not sure it's bug-free (especially the h263 (de)quant)
>
> Ok i integrated the C part of your code to XviD and i get a strange
> result with mpeg4 quantization (using your C code, not the reference
> one).
>
> ===============================================================================
> Test name: underworld-trailer
> Using cached first pass stats (hash - a1c5ab3ce4420b302dd41ee9886379ea)
>
> Results:
> xvid: Min PSNR y : 30,13 dB, u : 38,08 dB, v : 39,42 dB
> xvid: Average PSNR y : 38,72 dB, u : 42,98 dB, v : 45,27 dB
> xvid: Max PSNR y : 99,99 dB, u : 99,99 dB, v : 99,99 dB
> ===============================================================================
>
> I was getting 39.11 dB on average with the old code.
First things first: is dequantization (decoding) giving
exactly the same result?
> Before I go into deep debugging,
> id you sacrifice some precision step that we had in
> XviD ?
Partially, since it uses divide-by-multiply
[with variable fixed-point precision] instead of
the exact divide. Also: the bias are not the same
[Q/2 vs.(3*Q+2)/4, for intra]. What's the file size
difference?
But it might be a bug too.
> (if i remember correctly, you're also the author of the C quant
> code of xvid).
nope, i think it's Suxen_Drol
bye!
Skal
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