splitmuxsink conver 'running time' to absolute time

[Sebastian Dröge]

On Fr, 2015-12-11 at 12:09 +0100, Rini van Zetten wrote:
> Hi Sebastian,
> 
> The goal is to have the (capture) timestamp of the sender.
> 
> I read http://gstreamer-devel.966125.n4.nabble.com/Synchronization-of
> -multiple-senders-using-rtpBin-td4674390.html
> and implemented this to sync the receiver and the sender.
> 
> But is it achievable to convert the splitmuxsink running time to the
> (NTP) time of capture on the sender ?

Not easily as the NTP time is only known inside rtpbin and the elements
containing it. After rtpbin those times will be converted to the same
time on the clock used by the pipeline.

I'm not sure what the easiest solution to this problem would be,
probably making sure that you share a clock between all devices (e.g.
by using the GStreamer NetClient, NTP or PTP clock) and use that on all
the pipelines together with a base_time of 0. Then all buffer
timestamps arriving in splitmuxsink would be exactly the clock time.

Alternatively you can do all the calculations that are done in rtpbin
yourself again (by looking at the RTCP sender reports from the signal)
and then convert timestamps back from the local clock to the NTP clock.
But that's going to be a bit complicated.


One could also consider adding some kind of GstMeta with the
corresponding NTP times inside rtpjitterbuffer on all the buffers that
it's going to output. But that will require changes in rtpjitterbuffer,
not sure if that's an option for you.

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

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