[Mesa-dev] [PATCH 2/3] radeonsi: add sampling of 4:2:2 subsampled textures

[Grigori Goronzy]

On 29.08.2014 12:31, Andy Furniss wrote:
>> As for that 4:2:2 "doesn't work", AFAICT it absolutely does, but
>> there is no linear interpolation for chroma, so quality isn't ideal.
>> This seems to be a hardware restriction, unfortunately.
> 
> Hmm, we may have to disagree on the definition of working here :-)
> 
> Of course I don't understand the hardware - but are you saying that
> because the chrome needs horizontal interpolation you have to have
> vertical interpolation too?
>

No, I just observed that there is no linear interpolation horizontally.
I.e. the exact same chroma value is used for two pixels of the same block.

> 
> Tests were 1:1 vertical scale.
> 
> With weave shader a test pattern rgbymc 422 chroma looked much like it
> would if I had used ffmpeg to convert to it 420 (ie none of those at all
> rendered). On real video it bled between fields, so my use case of
> feeding it to a TV to deinterlace would fail - luma was OK.
>

Hmm - where can I find this test pattern?

I just made a simple test pattern myself: http://i.imgur.com/hsLFBxy.png
I displayed it in mpv with the following command line:
> mpv --vo=vdpau --vf=format=uyvy422 422-chroma.png

I clearly see separate chroma for each line, but chroma cositing seems
to be a bit off, i.e. chroma is shifted downwards by about half a pixel.
That doesn't happen with forced progressive mode. So this is most
probably it.

Grigori

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: OpenPGP digital signature
URL: <http://lists.freedesktop.org/archives/mesa-dev/attachments/20140829/34cd2a5c/attachment.sig>