[FFmpeg-devel] libavcodec/proresdec : add qmat dsp with SSE2, AVX2 simd

[Martin Vignali]

2017-10-07 18:16 GMT+02:00 Ronald S. Bultje <rsbultje at gmail.com>:

> Hi Martin,
>
> On Sat, Oct 7, 2017 at 11:49 AM, Martin Vignali <martin.vignali at gmail.com>
> wrote:
>
> > 2017-10-07 17:30 GMT+02:00 Ronald S. Bultje <rsbultje at gmail.com>:
> > > On Sat, Oct 7, 2017 at 10:22 AM, Martin Vignali <
> > martin.vignali at gmail.com>
> > > wrote:
> > > > Patch in attach add a new dsp
> > > > for manipulation of qmat
> > > >
> > > > for now, i move this code inside
> > > >
> > > > for (i = 0; i < 64; i++) {
> > > >         qmat_luma_scaled  [i] = ctx->qmat_luma  [i] * qscale;
> > > >         qmat_chroma_scaled[i] = ctx->qmat_chroma[i] * qscale;
> > > > }
> > > >
> > > > i add a special case for qscale == 1
> > > > and SSE2, AVX2 optimization
> > >
> > > This loop only executes once per slice. We typically do not
> SIMD-optimize
> > > at that level, because it won't give significant speed gains...
> >
> > Ok didn't know that.
> > I mostly follow, what there are already done, like in
> blockdsp.clear_block
> >
>
> Right, so consider that blockdsp is done per block (16x16 pixels), not per
> slice.
>
Ok on principle (only improve, a func which is called quite often)


>
> You could remove this entirely from the slice processing code by simply
> pre-calculating the values in the init function once for the whole stream,
> there's only 224 qscale values so it's 224*64*2 multiplications, which is
> (in the context of prores) virtually negligible.
>

Not sure, we can do that for prores decoder
the qmat seems to be set on the decode frame header func
(based on the header of the frame).

Martin