Pipeline simultanous starting time

Sebastian Dröge sebastian at centricular.com
Thu Dec 8 10:04:14 UTC 2016


On Wed, 2016-12-07 at 13:03 -0800, LC wrote:
> Thank! 
> As i need rtspsrc synchronization since first frame, i am switching to
> Sebastian Doge advise of using just one pipeline.
> Currently i am really confused because even if my ip cameras support
> https://tools.ietf.org/html/rfc6051, in Gstreamer is no support for that.
> But without that one, there is no way to synchronise since first frame.
> Anyway i am going to investigate if i have that extention header in RTP
> packets and if yes , than will setup that one pipeline with additional ntp
> parameters. As I understood piepline base time should be changed for that
> one pipeline. I also don't know why.

Adding support for RFC6051 to rtpjitterbuffer is not too difficult
really. You just have to a) pass the RTP header extension mapping from
the SDP to the jitterbuffer, and b) use the extension header from the
packets exactly the same way as the NTP time from the RTCP packets is
used currently.

However if you don't see the extension header mapping in the SDP of
your RTSP cameras, it's very unlikely that they send it. And if they
do, it would be in a non-standard way.

> As a last chance i will try to synchronize 2 separate pipelines. 

That's not going to make anything easier, you still have exactly the
same problem. What you're missing at this point is information from the
cameras about how to synchronize streams, without that you can't
implement any synchronization in no matter what way.

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