STREAMER Synchronizing multiple sources to a common receiver

[Sebastian Dröge]

On Sa, 2016-05-07 at 14:25 -0400, thiyagesh viswanathan wrote:
> 
> Questions I want to be answered:
> 1.Is my pipeline structure correct? 

Yes, the properties on rtpbin not so much though.

Use ntp-time-source=ntp (or unix). These two are going to use your
system clock, the setting you used will use the pipeline clock. The
pipeline clock is not going to be synchronized between all your
devices.

You might want to use rtcp-sync-send-time=false if both senders of you
have different latencies (camera, encoder, etc).

You might have to adjust the receiver pipeline latency to be high
enough for both senders. See gst_pipeline_set_latency().

ntp-sync=true and buffer-mode=synced are correct for your case.


Independent of that you need to ensure that RTCP between sender and
receiver is actually working, and synchronization will only be correct
after the first RTCP packet is received at the receiver. By default
after about 5 seconds. It can happen immediately if you set
rtp-profile=avpf on the rtpbin (well, not immediately but at some point
in the first second).

> 2.I am not modifying the pipeline clocks at all. Just assuming that
> the pipeline clocks of senders and receivers will be

If your system clocks are synchronized via NTP, then that's indeed not
necessarily needed.

> 3.synchronized once we sync the devices through NTP. Is this
> assumption correct?

> 4.Should I have just one rtpbin or separate rtpbin for each sender?

You can have one rtpbin for multiple sessions, and those sessions are
then all synced together. If you use multiple rtpbins instead, there
won't be any inter-session synchronization happening inside rtpbin.

> 5.Should i USE RTPJITTERBUFFER? if yes, should the mode be synced? 

rtpbin contains an rtpjitterbuffer already. Don't put a separate on
into your pipeline, otherwise you have two and the behaviour is not
very well then.


Does this all work better then? What is the behaviour you're seeing
now? Also does using one sender at a time result in smooth playback?

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

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