On 1/23/12, Mashiat Sarker Shakkhar <shahriman_...@yahoo.com> wrote:
>
>
> Doesn't mach my copy of spec or the ref-code. BFRACTION is only present
> in B-pictures, not P. My copy of ref-code says:
>
> if(vc1_InterlacedField == pPosition->ePictureFormat)
> {
> if(TRUE == pSeqParams->RefDistFlag)
> {
> if( (TRUE == vc1_PictureTypeIsRef(pParams->ePictureType[0]))
> ||
> (TRUE == vc1_PictureTypeIsRef(pParams->ePictureType[1]))
> )
> {
>
> which translates to (in lavc):
>
> if (v->fcm == ILACE_FIELD)
> {
> if (v->refdist_flag)
> {
> if (s->pict_type != AV_PICTURE_TYPE_B ||
> s->pict_type != AV_PICTURE_TYPE_BI)
> {
> ....
>
Thats actually not the relevant part.
The problem with the old code is that BFRACTION is not read if
refdist_flag is 0, however in the spec/reference decoder those two
elements are completely independent.
All my patch does is change this, so that BFRACTION is read for
b-frames, even if refdist_flag is zero.
It does not change when refdist is read (on reference frames, so not
B/BI), and does not change when BFRACTION is read (on B frames, B/BI)
That part of the lavc code you paraphrased is still untouched, i just
de-coupled refdist and bfraction. I could re-format the patch slightly
so that its more obvious (and less things are changed)
I guess it just seemed convenient to link refdist and bfraction at the
time, because they use the same condition in inverse.
- Hendrik
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