On Wed, Oct 25, 2023 at 9:03 PM Tomas Härdin <g...@haerdin.se> wrote:
> On Wed, 2023-10-25 at 21:00 +0200, Paul B Mahol wrote:
> > On Wed, Oct 25, 2023 at 8:39 PM Tomas Härdin <g...@haerdin.se> wrote:
> >
> > >
> > > > if (c) {
> > > > e[0] = 1 << 14;
> > > > e[1] = 0 << 14;
> > > > e[2] = v[1];
> > > > e[3] = v[0];
> > > > } else {
> > > > e[0] = v[0];
> > > > e[1] = v[1];
> > > > e[2] = 0 << 14;
> > > > e[3] = 1 << 14;
> > > > }
> > > >
> > > > if (invert2x2(e, d)) {
> > > > sum = UINT64_MAX;
> > > > goto next;
> > > > }
> > > >
> > >
> > > You can make use of the properties of e to simplify calculating the
> > > inverse. The determinant is always v[0]<<14, so you can just do if
> > > (!v[0]) continue; and skip the determinant check altogether.
> > >
> >
> > Even for real 2x2 matrix case? (Once one of rows is not 1, 0) ?
> > May added such cases later.
>
> You can just work the math out on paper. Inverse of
>
> 1 0
> v[1] v[0]
>
> is
>
> 1 0
> -v[1]/v[0] 1/v[0]
>
> not accounting for shifts.
>
But I want to add real 2x2 matrix with no 0 cell, with:
a, b
c, d
later. (even though gains are small, as encoded files use it rarely)
>
> Also RE: my other comments, you are right. I didn't take into account
> that MLP is lossless and that there may be off-by-one errors.
>
> And as I said on IRC you can formulate this as a least squares problem,
> then solve it using a linear system solve. This patch seems finds a
> solution that minimizes L1 rather than L2 though. Not sure what the
> implications of that are compressionwise. What happens if you replace
> FFABS() with a square for scoring?
>
It reduces size usually by less then 0.002 %
Linear system solver gives vectors to create equations for both channels at
same time?
>
> /Tomas
> _______________________________________________
> 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".
>
_______________________________________________
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".
