[vlc-devel] [PATCH] vout: opengl: add NV12/NV12 support

[Rémi Denis-Courmont]

Le dimanche 4 décembre 2016, 11:13:43 Thomas Guillem a écrit :
> > I have not had time to read my OpenGL paper book, so I can't comment on
> > the OpenGL aspects. But I think that the file is getting much too big,
> > but I don't like meaningless splits with tight dependencies between files
> > either :/
> > 
> > I would though think that chroma conversion belongs in a separate
> > conversion plugin. It might not be feasible without an opaque OpenGL
> > texture chroma type however.
> > 
> > Also, NV12 specifically is a hardware decoder output format. For sure, it
> > needs to be supported eventually... But does it really make sense at this
> > point, that the OpenGL output does not support pass-through, so the NV12
> > will be copied anyway. If copied, then conversion to I420 can be done on
> > the fly for free in SIMD. IIRC, Laurent even implemented that for x86
> > already.
> 
> Not really free, there is an extra memcpy when doing NV12 -> I420.

NV12->NV12 would need a copy in vlc_va_Extract() or equivalent, AFAIR. It 
wouldn't make sense for a software decoder to output NV12.

So why would there be an extra memcpy()? The SIMD code should copy and convert 
at the same time. Conversion from NV12 to I420 is really trivial.

IMO, this shader is vain until we have pass-through from hardware decoder to 
OpenGL. And by then, we should have a less monolithic OpenGL code base, so to 
speak.

P.S.: also patch title is wrong

-- 
Rémi Denis-Courmont
http://www.remlab.net/