On Tue, May 14, 2019 at 10:37:03PM +1000, Peter Ross wrote:
> On Sun, May 12, 2019 at 01:24:56PM +0200, Reimar Döffinger wrote:
> > On 12.05.2019, at 08:12, Peter Ross <pr...@xvid.org> wrote:
> > > +static int read_mb_value(GetBitContext *gb)
> > > +{
> > > + int v = 1;
> > > + int size;
> > > +
> > > + do {
> > > + size = 0;
> > > + if (!get_bits1(gb))
> > > + break;
> > > + v++;
> > > + do {
> > > + if (!get_bits1(gb))
> > > + break;
> > > + v += 1 << size++;
> > > + } while (size < 8);
> > > + } while (size == 8);
> > > +
> > > + if (size)
> > > + v += get_bits(gb, size);
> > > +
> > > + return v;
> > > +}
> >
> > Maybe not worth it performance wise, but did you check if this could be
> > simplified?
> > For example the get_bits1 cases that end up with size 0 could return
> > directly.
> > Or it could peek ahead 9 bits in the bitstream and count the leading 1s to
> > get v and size without looping (i.e. loop only for the 9 bits of 1s
> > specifically).
> > Alternatively add a comment to clarify the encoding scheme it implements
> > (like 9 consecutive 1s is a prefix encoding an offset of 257 etc).
>
> thanks for these suggestions.
>
> replacing get_bits() with OPEN_READER/UPDATE_CACHE/SHOW_UBITS/etc results in a
> consistent 0.50 % speedup.
Not sure how readable that gets, I actually just meant taking
advantage of show_bits()
While nice, I am not sure speed is much of a consideration for vp4
really.
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
To unsubscribe, visit link above, or email
ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
