[Libva] Add coefficients yuv to rgb conversion

[Emil Velikov]

On 4 November 2015 at 00:54, Gilles Chanteperdrix
<gilles.chanteperdrix at xenomai.org> wrote:
> On Tue, Nov 03, 2015 at 04:56:14PM +0000, Lionel Landwerlin wrote:
>> Hi,
>>
>> Following your comments on the previous patch, here is an serie to add
>> support for coefficients passed down to the EUs for the vpp yuv to rgb
>> conversion path.
>
> Hi,
>
> sorry for intruding on the mailing list, but this is a topic on
> which I worked recently. First question is: I implemented yuv to rgb
> conversion using GLSL shaders (only for yuv420p, but this could be
> easily implemented for other pixel formats), and the code is
> relatively simple:
> https://git.click-hack.org/vplayer.git/tree/lib/yuv420p_frag.glsl
> What is the gain of using libva instead?
>
I'm no expert in the libva code so take this with a grain of salt.

For doing things the GLSL way - you have an extra GL context
creation/management not to mention the overhead of
parsing/compiling/linking etc the GLSL shader. While the result (from
a hardware's perspective/instructions emitted) may be almost
identical, doing things within i965 libva driver should be less
CPU/memory intensive.

Regards,
Emil