[gst-devel] ffdec and QoS

Arnout Vandecappelle arnout at mind.be
Wed Jun 10 10:14:24 CEST 2009

On Tuesday 09 June 2009 19:48:07 Edward Hervey wrote:
> On Tue, 2009-06-09 at 19:18 +0200, Arnout Vandecappelle wrote:
> >  I have a pipeline like this:
> > souphttpsrc location=... do-timestamp=true ! mpeg4videoparse !
> > ffdec_mpeg4 ! \
> >  videoscale ! fakesink sync=true qos=true
> The problem with such a pipeline... is that due to the absence of
> queues, you will only have one-frame-duration in order to do:
>   * get more data from the httpsrc
>   * parse the video data
>   * decode it
>   * scale it
> If you were to put some queues before/after the decoder (even with very
> low limits), you'll have a dedicated thread for decoding... allowing you
> to always provide at least X buffers for display.

 Adding queues won't help, since it only adds to the latency... This pipeline 
was the result of starting from a playbin2 and stripping things down in order 
to localize the problem.

 By the way, "you will only have one-frame-duration": if decoding latency is 
longer than one frame, basetransform will _always_ drop, because every frame 
will arrive in the scale element after the next frame has arrived in the 


Arnout Vandecappelle                               arnout at mind be
Senior Embedded Software Architect                 +32-16-286540
Essensium/Mind                                     http://www.mind.be
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