[MEncoder-users] Mencoder and vdpau decoding

[Reimar Döffinger]

On Thu, Mar 19, 2009 at 10:44:33AM +0100, Robert Ramiega wrote:
> On Wed, Mar 18, 2009 at 08:01:08PM -0700, RC wrote:
> > On Wed, 18 Mar 2009 19:46:52 +0100
> > Robert Ramiega <jedi at plukwa.net> wrote:
> > 
> > >  For some time mplayer can use vdpau to accelerate decoding and
> > >  displaying of h264 among others. Now is there posibility to use this
> > >  in the decoding phase of mencoder? 
> > 
> > It wouldn't make much sense to do so.  The speed-up will in fact be
> > minimal.  Moving uncompressed video from a the GPU to system RAM isn't
> > free...
> 
>  Good point. I did not thought about that. Still this might gave some 1-2%
> of speedup and sometimes fixes or patches improve things by that factor 

Actually decoding can still be a good deal faster, the question is if
decoding speed is relevant compared to encoding.

>  Anyhow thanks to roo_ on #mplayer i found solution. My slow encodes where
> caused by some stuck almost year old libx264.so =o( Now encodes are like 3x
> faster (preliminary tests)

Given that it probably isn't with your encoder options.

> > Video encoders that run entirely on video-card GPUs are more promising,
> > but offer terrible quality and little speed improvement right now.
> 
>  You mean that say it's possible to encode video on Nvidia 8600M GT? Didn't
> know that.

Well, as he said at a horrible quality. If you make x264 use the same
bad quality you get about the same speed. Only advantage might be that
you could encode one video on the CPU and another on the GPU, but I
expect that at least CUDA is still as unusable for that use case as ever
(it really likes waiting actively for the GPU, i.e. using up 100% CPU
doing nothing but waiting for the GPU to finish, and working arounf that
problem is a pain and does not work all that well).