[FFmpeg-soc] [PATCH] jpeg2k : support higher sample precision

[Michael Niedermayer]

On Wed, Jun 24, 2009 at 05:59:19PM +0000, Jai Menon wrote:
> On Wed, Jun 24, 2009 at 3:58 PM, Michael Niedermayer<michaelni at gmx.at> wrote:
> > On Wed, Jun 24, 2009 at 01:42:08PM +0000, Jai Menon wrote:
> >> On Wed, Jun 24, 2009 at 1:27 PM, Michael Niedermayer<michaelni at gmx.at> wrote:
> >> > On Sun, Jun 21, 2009 at 04:35:20PM +0000, Jai Menon wrote:
> > [...]
> >> > [...]
> >> >> @@ -806,6 +815,26 @@
> >> >>
> >> >>          line += s->picture.linesize[0];
> >> >>      }
> >> >> +    } else {
> >> >> +        for (; y < tile->comp[0].coord[1][1] - s->image_offset_y; y++) {
> >> >> +            uint16_t *dst;
> >> >> +            x = tile->comp[0].coord[0][0] - s->image_offset_x;
> >> >> +            dst = line + x * s->ncomponents * 2;
> >> >> +            for (; x < tile->comp[0].coord[0][1] - s->image_offset_x; x++) {
> >> >> +                for (compno = 0; compno < s->ncomponents; compno++) {
> >> >
> >> >> +                    *src[compno] = av_rescale(*src[compno], (1 << 16) - 1,
> >> >> +                                              (1 << s->cbps[compno]) - 1);
> >> >
> >> > av_rescale is too slow
> >>
> >> So just (*src[compno]/((1 << s->cbps[compno]) - 1)) * ((1 << 16) - 1) ?
> >
> > * is slow
> > / s slower
> >
> > "src" << C
> > it should be
> 
> <possibly dumb question ahead>
> 
> I understand that * and / are slower but how can I achieve the same
> effect with a single <<?

well, not the same but close enough IMHO
src<<C
or
(src<<C) + (src>>(16-C))
should be close enough, my point was mainly that av_rescale() is too slow
to be done per pixel and anything else is better

it also might be possible to merge the rescaling into some other previous
step

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If you think the mosad wants you dead since a long time then you are either
wrong or dead since a long time.
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