[FFmpeg-devel] [PATCH] avcodec: add Actimagine VX video decoder

[Paul B Mahol]

On Tue, Mar 16, 2021 at 8:22 AM Florian Nouwt <fnouwt2 at gmail.com> wrote:

> Alright, I'll just convert to rgb then. Both the windows codec and the ds
> decoder decode the subsampling by simply duplicating the u/v samples within
> a 2x2 block (no interpolation). Should I do that too? Or would
> interpolation be preferred? As far as I was able to see the windows codec
> takes the average of 2x2 blocks to create the subsampled data.
>

That is unacceptable non-solution.


>
> Op ma 15 mrt. 2021 23:35 schreef Hendrik Leppkes <h.leppkes at gmail.com>:
>
> > On Mon, Mar 15, 2021 at 10:55 PM Florian Nouwt <fnouwt2 at gmail.com>
> wrote:
> > >
> > > Now that I think about it, it might not be possible to an accurate
> > > straightforward conversion to regular yuv because of the subsampling.
> > The u
> > > and v cannot just linearly be scaled to line up with the required
> values
> > > for regular yuv. That would mean the output would have to be in rgb
> > format.
> > > It wouldn't really be an issue, but not the most elegant solution.
> > Wouldn't
> > > it be possible to support these alternative coefficients in libswscale
> or
> > > so? I suppose that would still give issues with applications that have
> > > their own conversion algorithms.
> > >
> >
> > I don't think a single game codec warrants creating an entirely new
> > pixel format for, unless it has a concrete independent definition and
> > is used outside of this codec as well.
> > Otherwise, the conversion logic looks rather straight forward and
> > relatively cheap, and should probably just output RGB (either packed
> > or planar, whichever is easier). It does remind me a bit of YCgCo, but
> > with different  formulas unfortunately.
> >
> > - Hendrik
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