Mailinglist Archive: radeonhd (365 mails)

[Yang Zhao <yang@xxxxxxxxxx>]

2009/3/4 Matthias Hopf <mhopf@xxxxxxx>:
> On Mar 03, 09 18:03:22 -0800, Yang Zhao wrote:
> > The texture sampler for CbCr used to be configured to use bilinear
> > interpolation when upscaling. This results in a smoothing of the
> > chroma channels, and is perceived as being blurry when a lot of sharp
> > changes in colour is present. Simply flip the bits to use
> > nearest-point interpolation instead.
>
> Yang, I wouldn't change that. AFAIU color subsampling in the normal
> YCb'Cr' color spaces is defined to be interpolative. If it does look to
> blurry, there could be a different bug. Also, with nearest-neighbor
> interpolation at least I always stumble over hard edges at smooth
> surfaces, especially if they are red.

Does MPEG/BT.601/BT.709 define an upscaling method for chroma when
decoding, or is that up to each decoder implement as they see fit? I
failed to find any secondary source information on this, and acquiring
specs myself is a PITA.

In any case, I was purely going by user feedback and comparing results
to the mplayer software converter: http://yangman.ca/r600_xvtest/

The blurring is very, very subtle, and, frankly, neither bilinear nor
nearest-point produces very good results for images with a lot of file
detail. On the other hand, bilinear clearly does lose a lot of detail,
and it comes down to a question of whether we want sharp images with
some red artifacts, or slightly fuzzy images with less said artifacts.

Alternatively, we try bicubic filtering with the shader. (Actually, I
think I'll try that for kicks anyway.)

-- 
Yang Zhao
http://yangman.ca
-- 
To unsubscribe, e-mail: radeonhd+unsubscribe@xxxxxxxxxxxx
For additional commands, e-mail: radeonhd+help@xxxxxxxxxxxx