[FFmpeg-devel] [PATCH][RFC] avcodec: disallow hwaccel with frame threads

[wm4]

On Wed, 20 Jan 2016 00:42:18 +0000
Andy Furniss <adf.lists at gmail.com> wrote:

> Hendrik Leppkes wrote:
> 
> >>> I do not agree that it should be a warning. As outlined in the
> >>> commit message and this thread, there are serious flaws with
> >>> frame threading and hwaccel.  
> >>
> >> I'm fine with it being an error, but since it is an API change, it
> >> should follow the usual deprecation period to allow downstream
> >> users time to fix it. Meanwhile it can be a warning so that people
> >> notice the problem.  
> >
> > Its fundamentally broken, and making it a warning would re-introduce
> > known crashes. So no.  
> 
> So are the flaws in ffmpeg or particular drivers?
> 
> It does seem a shame perf wise, I've been testing my AMD UVD decode
> recently and for 500 UHD frames in a really high bitrate h264 file it's
> like -
> 
> ffmpeg threaded = 16 sec.
> 
> ffmpeg single thread = 20 sec.

With or without hwaccel?

> 
> gstreamer vaapi 14 sec.
> 
> gstreamer omx 10 sec.
> 
> the omx is a faster as the others do nv12 -> I420 on cpu (AFAICT)
> 
> Maybe -threads 1 hurts perf by limiting the format conversion as well?
> 
> Is there a way to get whatever the h/w spits out (nv12) directly? Trying
> to ask for nv12 seemed to get a double conversion.

Both vdpau and vaapi can retrieve image data as nv12.