[FFmpeg-devel] [libav-devel] [RFC] M-bit to N-bit YUV conversions

[Oskar Arvidsson]

On Wednesday 24 August 2011 18.55.10 Ronald S. Bultje wrote:
> [...]
>
> Dither is all just because of ordered dither and I don't feel it's
> worth looking into. I've been planning to replace it with
> Atkinson-style dither (that's like f-s, which x264 uses) so let's just
> work towards that and be done with it.

Still, ordered dither would actually work as intended if only using simple 
shifting. Also, I think the underlying problem would be the same with any type 
of dither as what the current conversion method does is to increase the values 
- thus posing larger errors in e.g. error diffusion if not the "byte 
duplication" is reversed in one or another way.
 
> > b) Should we distinguish between limited and full range YUV?
> 
> Doesn't convertJpegRange already do that? Are you afraid that we
> become "out of range" when we scale between bitdepths with different
> ranges? (I admit I haven't looked much into that yet, i.e. don't know
> how to handle it yet.)

I'm not too worried about becoming out of range, but the fact that to my 
knowledge there's no distinction between limited and full range YUV in swscale 
at the moment - having different methods for these would require more work and 
would also mean we have to discuss user options etc.

Oskar

--
Oskar Arvidsson
+46 (0)701766451
oskar at irock.se