[FFmpeg-devel] [PATCH] bink: perform scan order permutation of quantization matrices in read_dct_coeffs()

[Peter Ross]

On Sun, Feb 13, 2011 at 07:41:32AM +0100, Kostya wrote:
> On Sun, Feb 13, 2011 at 02:32:58PM +1100, Peter Ross wrote:
> > This fixes visual glitches in Bink version 'b' files, as the quantization tables
> > were not being permutated.
> > ---
> >  libavcodec/bink.c     |    4 +-
> >  libavcodec/binkdata.h |  618 ++++++++++++++++++++++++-------------------------
> >  2 files changed, 303 insertions(+), 319 deletions(-)
> > 
> > diff --git a/libavcodec/bink.c b/libavcodec/bink.c
> > index 928bf53..5ebf98c 100644
> > --- a/libavcodec/bink.c
> > +++ b/libavcodec/bink.c
> > @@ -678,8 +678,8 @@ static int read_dct_coeffs(GetBitContext *gb, DCTELEM block[64], const uint8_t *
> >  
> >      block[0] = (block[0] * quant[0]) >> 11;
> >      for (i = 0; i < coef_count; i++) {
> > -        int idx = coef_idx[i];
> > -        block[scan[idx]] = (block[scan[idx]] * quant[idx]) >> 11;
> > +        int idx = scan[coef_idx[i]];
> > +        block[idx] = (block[idx] * quant[idx]) >> 11;
> >      }
> 
> 1) permutation depends on DCT type selected. Maybe in future Jason will
> fullfill his promise and write optimised DCT for Bink and it will require
> different permutation. Then decoder will be broken.

True. My oops, the critical lines should therefore be:

        int idx = coef_idx[i];
        block[scan[idx]] = (block[scan[idx]] * quant[bink_scan[idx]]) >> 11;

> 2) you generate bink-b tables anyway so you can permutate them during creation
> unlike static data we have for latter Bink versions.

Ok, for now. We'll need to revisit this when the Bink encoder is committed.

-- Peter
(A907 E02F A6E5 0CD2 34CD 20D2 6760 79C5 AC40 DD6B)
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