[MPlayer-users] Disable colospace conversion

[Carl Eugen Hoyos]

Andy Furniss <adf.lists <at> gmail.com> writes:

> Umar Qureshey wrote:
> > I am trying to figure out what the CPU load is when 
> decoding an H.264 stream but without the colorspace 
> conversion.

As explained by Andy, use -vo null
Additionally, I believe you will need -nosound -benchmark

> > Is there a way in mplayer to just decode a file and 
> > not do colorspace conversion?
> 
> CSC is normally done by the -vo so normally hardware 
> (gpu) eg. -vo xv or gl or vdpau but may be done by 
> cpu eg -vo x11.

This is at least very misleading.
You are right that vos internally (can) do some 
colourspace conversion but - at least imo - that is 
irrelevant (since it should happen on the GPU) as 
long as we are talking about software OpenGL.
But this conversion only takes a small number of 
colour spaces as input (often only YV12) and the 
problem is to provide YV12. Avoiding this conversion 
can mean a large performance gain, see prores with 
-vo gl_nosw vs xv or gl.

> So I suppose -vo null will do what you want but some 
> of the difference in cpu usage you see may not be CSC 
> but because you are avoiding really displaying which 
> may (depending on -vo implementation details) show 
> extra cpu use when waiting to vsync with the display.

I am not convinced about your reasoning but -vo null 
can definitely be used to test "playing" (decoding) 
performance without colour space conversion.

> I assume -vo null will also avoid a mem copy as well.

This is not generally correct, the memcopy isn't always 
needed for actual playback either (direct rendering).

If this is about yuv420p -> rgb15 (or 16) on arm, then, 
yes such a patch would be very welcome on ffmpeg-devel;-)

Carl Eugen