[FFmpeg-devel] LIBMPEG2_BITSTREAM_READER vs. golomb.h

[Michael Niedermayer]

On Mon, Jul 14, 2008 at 04:28:03AM +0100, M?ns Rullg?rd wrote:
> Michael Niedermayer <michaelni at gmx.at> writes:
> 
> > On Mon, Jul 14, 2008 at 12:02:47AM +0100, M?ns Rullg?rd wrote:
> >> I just spent some time bug-hunting, only to discover that the
> >> exp-golomb functions in golomb.h do not work with
> >> LIBMPEG2_BITSTREAM_READER.  This is because they rely on more than the
> >> promised 17 bits to be available after an UPDATE_CACHE() call.
> >> 
> >> To avoid future mishaps, I was thinking of adding a preprocessor check
> >> to golomb.h (I'm too lazy to try to make it work). 
> >
> > try:
> > @@ -64,10 +63,12 @@
> >
> >          return ff_ue_golomb_vlc_code[buf];
> >      }else{
> > -        log= 2*av_log2(buf) - 31;
> > -        buf>>= log;
> > +        log= 31 - av_log2(buf);
> 
> Doesn't this still assume that the 1 bit is somewhere in the bit
> cache?  That won't be the case if there are more than 16 leading
> zeros.

Which syntax element of H.264 may have more than 16 leading zeros?


[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Good people do not need laws to tell them to act responsibly, while bad
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