[FFmpeg-devel] [PATCH] Escape 124 (RPL) decoder

[Michael Niedermayer]

On Thu, Mar 27, 2008 at 10:18:37PM -0700, Eli Friedman wrote:
> On Thu, Mar 27, 2008 at 8:49 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
[...]
> >  [...]
> >  > +static uint32_t rice_decode(GetBitContext* gb) {
> >  > +    uint32_t more_bits, value;
> >  > +
> >  > +    more_bits = get_bits1(gb);
> >  > +    value = more_bits;
> >  > +    if (!more_bits)
> >  > +        return value;
> >  > +
> >  > +    more_bits = get_bits(gb, 3);
> >  > +    value += more_bits;
> >  > +    if (more_bits != (1 << 3) - 1)
> >  > +        return value;
> >  > +
> >  > +    more_bits = get_bits(gb, 7);
> >  > +    value += more_bits;
> >  > +    if (more_bits != (1 << 7) - 1)
> >  > +        return value;
> >  > +
> >  > +    more_bits = get_bits(gb, 12);
> >  > +    value += more_bits;
> >  > +    return value;
> >  > +}
> >
> >  This can be simplified, also why is it called rice?
> 
> The person who wrote up the bitstream description for this codec
> called it RICE_Decode; do you have a better suggestion?

vlc_decode(), not really the best name either but at least it is not outright
wrong.


> 
> >  Why this odd decode into these weird arrays and then copy into the frame
> >  with the above function? IMHO decode one superblock and then copy that into
> >  the frame.
> 
> Would you prefer the code to insert the macroblocks as it generates them?

Yes, or to hava a single superblock be build and then copied. The idea
here is that a superlock does fit in the L1 cache, a frame does not.


> 
> That'll mean I have to figure out how to keep around the previous
> frame... what's the preferred way to do that?  Decode into a private
> buffer and memcpy the result into the returned frame?

Just keep the previous AVFrame in the context.

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I wish the Xiph folks would stop pretending they've got something they
do not.  Somehow I fear this will remain a wish. -- M?ns Rullg?rd
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