[XviD-devel] [BUG] DC thresholding

[Christoph Lampert]

Hi,

the way I see it from a quick glance, the routines tries to do the right
thing: 
It uses the "quant" parameter only for this check, whereas for
quantization, iQuant=pMB->quant is used. 

So, it seems it's just the call to decoder_mbintra() that is wrong,
passing current quant instead of previous, right? That should be quick to
fix. 

gruel





On Wed, 29 Oct 2003, Edouard Gomez wrote:
> Seen on the forum:
> http://www.xvid.org/modules.php?op=modload&name=phpBB2&file=viewtopic&t=1595&highlight=
> 
> <quote>
> According to ISO/IEC 14496-2 table 6-21, the QP is the quantization
> parameter of previous coded marcoblock, except for the first coded MB.
> 
> However, in XVID decoder.c, I found the following trouble:
> 
> if (quant < intra_dc_threshold) {
> int dc_size;
> int dc_dif;
> .................
> .................
> } else {
> start_coeff = 0;
> }
> 
> where quant = mb->quant, it's QP of current MB, not previous MB.
> So it does not consist with the standard.
> </quote>
> 
> I confirm  that devapi4 still  has this and  i've read the  standard, it
> seems he's right. Anyone with spare time to spend on this (I have not) ?
> 
> -- 
> Edouard Gomez
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