STREAMER Synchronizing multiple sources to a common receiver

[thiyagesh viswanathan]

Thank you for the quick response. I tested it out and it works very well. Though there are little latency variations. It remains < 30 ms most of the time.Though sometime it extends to more that 60 Frame rate is 15). The video playback is smooth.  I still have few questions though,

1.Will my situation improve even more if I sync pipeline clocks? 
2, Is there any way to calculate the relative latency between the streams from both sources? I am assuming that I have to create my own plugin. What methods does streamer allow to achieve what I want. Even better if there is an existing plugin which I can study. 
3. For the set_pipeline_latency() element, I just set the rtpbin latency in my pipeline to 500 ms. Is that fine? I mean I am not using c code for now. Just playing with the pipelines. 

Thanks in advance. 
> On May 10, 2016, at 2:59 AM, Sebastian Dröge <sebastian at centricular.com> wrote:
> 
> 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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