[Libva] Add coefficients yuv to rgb conversion

[Gilles Chanteperdrix]

On Thu, Nov 05, 2015 at 02:13:29PM +0000, Emil Velikov wrote:
> 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.

Well, compiling/linking the GLSL shader happens only once at
initialization. The advantage I see with a GLSL shader is that it
looks more portable, OpenGL with GLSL is almost universally
available, whereas libva runs on Linux only.

-- 
					    Gilles.
https://click-hack.org