Pipeline not prerolling when tee has more than one src-pad

[Sebastian Dröge]

On So, 2014-12-28 at 21:39 +0100, Jannis wrote:
> Hi list,
> 
> I'm using gstreamer-1.2.4 and create a videostream with this pipeline:
> 
> gst-launch-1.0 videotestsrc !
> video/x-raw,width=640,height=360,pixel-aspect-ratio=1/1,framerate=25/1 !
> timeoverlay ! clockoverlay deltay=50 ! vp8enc threads=2 deadline=35000 !
> matroskamux streamable=true ! gdppay ! tcpserversink host=127.0.0.1
> port=5000
> 
> When I display it using:
> 
> gst-launch-1.0 tcpclientsrc host=127.0.0.1 port=5000 ! gdpdepay ! tee
> name=stream ! decodebin ! videoconvert ! ximagesink
> 
> everything is fine and the image is displayed. When I append another
> element getting its data from the tee element:
> 
> gst-launch-1.0 tcpclientsrc host=127.0.0.1 port=5000 ! gdpdepay ! tee
> name=stream ! decodebin ! videoconvert ! ximagesink stream. ! fakesink
> 
> the pipeline gets stuck in the PREROLLING state. Adding queues after the
> tee and "stream.":
> 
> gst-launch-1.0 tcpclientsrc host=127.0.0.1 port=5000 ! gdpdepay ! tee
> name=stream ! queue ! decodebin ! videoconvert ! ximagesink stream. !
> queue ! fakesink
> 
> doesn't help, too.

Adding queues is definitely necessary here, without you can't expect it
to work at all.

When you run it with queues, does it help if you make the limits of the
queues bigger? Also you should see from the debug logs if at the end one
of the queues is full and the other empty. In that case the queue limits
were too small.
Also the async setting on the sinks could make a difference here. One
potential problem could be that the decoder drops quite some data in the
beginning (until the first keyframe) while the fakesink already consumed
a buffer and waits for the ximagesink to preroll... which then never
happens because at some point the queue before the fakesink is full.

-- 
Sebastian Dröge, Centricular Ltd · http://www.centricular.com
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