[vlc-devel] [PATCH] transcode: Fix multithreaded encoding

[Rafaël Carré]

On Mon, 8 Nov 2010 17:42:22 +0200
Ilkka Ollakka <ileoo at videolan.org> wrote:

> On Mon, Nov 08, 2010 at 04:34:29PM +0100, Rafaël Carré wrote:
> > Le 08/11/2010 15:59, Rafaël Carré a écrit :
> 
> > >      id->p_encoder->i_threads = p_sys->i_threads;
> > >+    /* We pass down the number of desired threads to the encoder
> > >(avcodec/x264)
> > >+     * But why would we want to run encoder asynchronously to the
> > >decoder ?? */
> > >+    p_sys->i_threads = 0;
> 
> > Note, this patch is functionally equivalent to removing all the
> > "if(thread >= 1)" code and EncoderThread().
> 
> Like mentioned in IRC, I'm more in favor of removing if(thread > 0 )
> and EncoderThread() alltogether, as it would clean up the code. It's
> unlikely anyway that someone would fix current threading code in
> transcode.
> 
> > I just thought this smaller patch would help looking at the issue :)

I benchmarked this patch:

time cvlc --ignore-config --no-media-library --no-ffmpeg-hw --no-audio
--no-sout-audio --stop-time=10 big_buck_bunny_1080p_h264.mov --sout
"#transcode{vcodec=h264,threads=4,venc=x264{preset=slow,trellis=2},vb=2000}:std{access=file,dst=$HOME/out.ts}"
vlc://quit

gives:
 90,26s user 1,02s system 234% cpu 38,927 total	  with HEAD
113,34s user 0,54s system 242% cpu 46,971 total   with the patch

on i3, 4 cores @ 2.93GHz 

-- 
✍ Rafaël Carré ☺
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