[Mesa-dev] Status of external image with yuv format support in Mesa

[Pohjolainen, Topi]

On Tue, Jul 29, 2014 at 05:10:09PM -0400, enpeng xu wrote:
>    Hi Topi,
> 
>    On mesa mailing list,I saw you posted some patches for supporting
>    OES_external_image externsion, you also added yuv buffer format support,
>    it's really useful, but looks like just part of codes merged into mesa,
>    can you let me know why? what's the status of your patch?

There the yuv support dealt specifically with formats NV12 and YV12 where
where luminance and chroma components are located in separate planes. In terms
of i965 this meant sampling of multiple texture images per one sampler, and
imposing a few difficulties. First, the i965 backend would need to be
augmented to support multiple surfaces per sampler. Second, the program would
need to be augmented with additional instructions converting YUV samples into
RGB equivalent. Neither is trivial to implement or to maintain, and impose
addtional constraints to the maximum number of textures to be supported and to
the number of available hardware registers for the rest of the program.

Hence people were more inclined to an implementation that would be based on
latest native hardware support. For example, there is now possibility
to sample YUV formats with one hardware surface as long as Y is in its own
plane and UV is packed in another.
Unfortunately in the end priorities got shifted and I dropped the ball.

Thanks,
Topi