rtsp source synchronisation

[Liene Cirule]

Many thanks for the response.

I posted my answers to mailing list. :)

Sure, I have no problems to make some code, but it's necessary to
understand what kind of components should i set there. And do I have to run
some unix deamon to get reference clock for all my devices. Or it's not
strictly necessary.

On Mon, Nov 28, 2016 at 11:32 PM, Sebastian Dröge <sebastian at centricular.com
> wrote:

> On Tue, 2016-11-22 at 06:27 -0800, LC wrote:
> > Hei, hei!
> >
> > I am testing rtsp stream synchronization abilities.
> > My use case is like this : 2 rtsp live streams in 2 filesinks.
> >
> > I am not going to use any mux element to get done synchronization inside
> > that element. Otherwise i need to demux to get each frame from each
> specific
> > rtspsrc to specific filesink.
>
> What are your RTSP senders? GStreamer based or something else? If
> something else, what kind features does that software stack give you,
> what kind of configuration related to synchronization and time can you
> do?
>
> > I am testing with this pipeline and want to get first frame synchronised
> but
> > i can't find the correct way. Here is that pipeline: gst-launch-1.0 -e
> > rtspsrc rfc7273-sync=true ntp-time-source=running-time
> > location=some/media.smp ! rtph264depay ! h264parse ! mp4mux ! filesink
> > location=file115.mp4 rtspsrc rfc7273-sync=true
> ntp-time-source=running-time
> > location=some/media2.smp ! rtph264depay ! h264parse ! mp4mux ! filesink
> > location=file145.mp4
>
> In what way do you want the two files to be synchronized? They should
> start with exactly the same frame, or ...?
>
> > I also noticed comment on rfc7273-sync feature : "(requires clock and
> offset
> > to be provided)". And how can i share it, where to specify it ?
>
> RFC7273 requires the RTSP senders to a) use a known clock (e.g. a
> NTP/PTP, GPS, etc clock) and b) to put the information about this clock
> (which one it is) and how the media relates to it (i.e. an offset
> between the clock epoch and the RTP timestamp) into the SDP.
>
> If that is given, then you can make use of the RFC7273 feature on the
> receiver side to get accurate synchronization based on that clock and
> when the media was captured according to that clock.
>
> Otherwise you might still have some other options (e.g. if you know
> that the senders are synchronized to a specific NTP clock and advertise
> this in their RTCP packets), but nothing standardized or simple that
> works without configuration. It completely depends on your setup then.
>
> --
> Sebastian Dröge, Centricular Ltd · http://www.centricular.com
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> gstreamer-devel at lists.freedesktop.org
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>
>
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