[gst-devel] long pauses during rtsp playback

[Marco Ballesio]

Hi,

On Sun, Oct 17, 2010 at 7:28 PM, Doug Crawford <dcraw101 at yahoo.com> wrote:

>
> I tried setting sync=true, but then I don't see any video image at all.


I suspect your video sink is discarding all the frames because they're
arriving too in late. If the element (and the framework) has been compile
with debug enabled, try
export GST_DEBUG=TIDmaiVideoSink:5 prior executing the pipeline and see
whether any output in that sense is given.


> I am
> guessing this is the root of the problem.  Is there any element that might
> fix or help synchronize the RTP timestamps?
>

This is a built-in design mechanism in GStreamer. See here:

http://cgit.freedesktop.org/gstreamer/gstreamer/tree/docs/design/part-qos.txt
(I guess you can safely skip to the GstBaseSink and buffer dropping
description).

A possibility would be to try and reduce the jitter buffer depth in the
rtspsrc element, but the default is normally good enough. Imo the video sink
element you're using needs some improvements. I'm not too fond it'll work,
but maybe you could try and replace it with v4l2sink. There are (scarce)
possibilities fdbevsink will work.


>
> I suspect the problem is in the TIDmaiVideoSink because if I run the
> gstreamer rtsp client on my Ubunutu box the video is very smooth (although
> it is delayed about 2 seconds which I believe is related to a latency
> parameter on the rtspsrc element).  I can only run the rtsp client on my
> ubuntu box using playbin2.


I share your idea about the video sink ;)


> If I try to compose the pipeline using
> inidividual elements like: "gst-launch rtspsrc
> location=rtsp://10.5.5.33/mpeg4/media.amp ! rtpmp4vdepay ! ffdec_mpeg4 !
> videoscale ! xvimagesink" then I get the following error:
> /GstPipeline:pipeline0/GstRTSPSrc:rtspsrc0/GstUDPSrc:udpsrc1: Internal data
> flow error.
> Additional debug info:
> gstbasesrc.c(2507): gst_base_src_loop ():
> /GstPipeline:pipeline0/GstRTSPSrc:rtspsrc0/GstUDPSrc:udpsrc1:
> streaming task paused, reason not-negotiated (-4)
>

mmhhh, you should put a few caps for indicating at least the payload type,
something like the examples in:

http://www.gstreamer.net/data/doc/gstreamer/head/gst-plugins-good-plugins/html/gst-plugins-good-plugins-gstrtpbin.html

for when the rtpbin is used as a source element.


>
> Is there any way to see exactly what playbin2 is using for its pipeline.
>

if you're interested in the pipeline structure, you can dump a dot file
(Google is your friend).


> There must be some other element that I am missing.  Also, if I try to play
> the video on my OMAP3EVM using playbin2 then I only see 1 frame and then
> the
> video pauses indefinitely.
>

another symptom of a bad latency handling in the sink.. If it's not the
case, _maybe_ adding a queue before the sink could help (I'm just wondering
whether it could be a deadlock).

Regards


> --
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> Sent from the GStreamer-devel mailing list archive at Nabble.com.
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