[FFmpeg-devel] [PATCH] v3: lavu/pixdesc: favour formats where depth and subsampling exactly match

[Philip Langdale]

On Thu, 15 Sep 2022 23:25:54 +0200
Michael Niedermayer <michael at niedermayer.cc> wrote:

> > +
> > +        if (dst_desc->log2_chroma_h < src_desc->log2_chroma_h) {
> > +            loss |= FF_LOSS_EXCESS_RESOLUTION;
> > +            score -= 32 << (src_desc->log2_chroma_h -
> > dst_desc->log2_chroma_h);
> > +        }  
> 
> with 16bit 4:2:0 
> to
> 14bit 4:2:0
> vs.
> 16bit 4:4:4
> 
> more data is preserved in the later but the 420->444 would have a
> loss of 64 i think and 16->14 i think 8. I didnt try this just
> reading the code so i may be missing something but i think the code
> would favor the lower bitdepth That may be unexpected

Yep. Another edge case :-)

I've posted a v4 that adjusts the excess resolution penalty to avoid
this.

Maybe I've got it right this time.

Thanks,

--phil