[gst-devel] ffdec and QoS

Wim Taymans wim.taymans at gmail.com
Wed Jun 10 10:33:07 CEST 2009

On Wed, 2009-06-10 at 10:15 +0200, Arnout Vandecappelle wrote:
> On Tuesday 09 June 2009 19:50:29 Wim Taymans wrote:
> > >  The core of the problem, I think, is that the QoS handling doesn't take
> > > into account pipeline latency.  It just assumes that throughput =
> > > 1/latency and doesn't seem to take into account that data can be buffered
> > > in the pipeline.
> >
> > QoS does take latency into account (or else RTSP or RTP streams would
> > never play). It's probably that ffmpeg totally does not specify its
> > latency and thus it seems that buffers are simply arriving too late.
> > Adding a meaningful reply to the LATENCY query in ffmpeg will likely
> > solve this.
>  Sounds good.  How does ffmpeg know the latency, though?  It buffers one 
> frame, but since the framerate is unknown you can't convert this to time, can 
> you?

The thing is that the latency query will be done when the sink prerolls,
which means that the decoder has at least decoded and pushed 1 buffer.
You could use the info you got from decoding this buffer to answer to
the latency query.


>  Regards,
>  Arnout

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