Random delay and sync for audio for rtsp?

[Peter Maersk-Moller]

Hi Tim.

Please see replies in-line.

On Thu, Nov 27, 2014 at 9:33 AM, Tim Müller <tim at centricular.com> wrote:

> > I am wondering if rtspsrc currently, in 1.4.4 used in uridecodebin and
> > playbin, is unable to sync audio and video correctly if the stream is
> > live as opposed to VoD? Anybody who knows?
>
> This is with UDP being used as transport?
>

Not only UDP. Both UDP and TCP.


> > WARNING: from
> > element
> /GstPipeline:pipeline0/GstAutoVideoSink:autovideosink0/GstXvImageSink:autovideosink0-actual-sink-xvimage:
> A lot of buffers are being dropped.
> > Additional debug info:
> > gstbasesink.c(2789): gst_base_sink_is_too_late
> > ():
> /GstPipeline:pipeline0/GstAutoVideoSink:autovideosink0/GstXvImageSink:autovideosink0-actual-sink-xvimage:
> > There may be a timestamping problem, or this computer is too slow.
> >
> >
> > And as result the video window is only updated very slowly with new
> > frames. Now the computer is hardly doing anything, so it is not slow.
> > I'd rather suspect there is a timing issue.
>
> This is often an indication that some element(s) in the pipeline don't
> handle the latency query correctly, or there are elements that don't
> advertise the correct amount of latency.
>

So what can I do about it? The pipeline is rather simple

    gst-launch-1.0 -v uridecodebin uri=rtspt://SOMETHING/something
name=decoder ! autovideosink decoder ! autoaudiosink

Ok, admittedly, the actual pipeline that eventually is constructed by the
bin is far from simple, but that is outside my control.
Anything I can do to debug or trace the error?

That aside (being slow/latency report problem) it seems that gstreamer (at
least in some cases) can't sync a live stream correctly. Do you agree that
may be the case? In my case I stream from FMLE over the Wowza server
(taking a flash stream and making it available for rtsp). Is there a way we
can construct a simpler test case? I'm not familiar with the GStreamer
rtsp-server. Perhaps we reproduce the fault with that? I can also make the
Live rtsp stream from the Wowza server available if somebody is interested
in checking out the stream, but in that case please email me to set it up
as I have to start FMLE to make it work.

Cheers
Peter Maersk-Moller
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