Low Latency On Udp Multicast Streaming

[Nicolas Dufresne]

Le samedi 07 décembre 2019 à 14:07 -0600, Osman Berk a écrit :
> Hello I am using gstreamer for low latency udp multicast streaming. I had
> problem with delay, which was around 1 second.
> 
> After I used rtph264pay instead of mpegtsmux the delay is gone. 
> 
> My question is why did this happen, is there a delay problem with mpegtsmux
> element, and can I add audio rtph264pay, if so how?

MPEG TS demuxer adds by default 700ms latency. This is the worst case
scenario to ensure we can produce valid timestamp. Of course, a muxer
could be configured to operate with much lower latency, but there is no
in-stream indication.

In future release of GStreamer, tsdemux (and tsparse) will have a
latency property that application that controls the muxer can use to
reduce the latency. You need strong knowledge of MPEG TS to know this
value of course.

With recent GStreamer version (e.g. 1.16), you can use the latency
tracer to get the reported and effective per element latency. I've
presented about that at the Gst Conf this year.

https://gstconf.ubicast.tv/permalink/v125d173da4d6ffimx2s/#start=1922


> 
> old transmitter:
> 
> src ! x264enc tune=zerolatency ! mpegtsmux ! udpsink host=234.1.1.1
> port=1234
> 
> old receiver:
> 
> gst-launch-1.0 udpsrc adress=234.1.1.1  port=1234 ! queue ! tsparse !
> tsdemux ! queue ! h264parse ! avdec_h264 ! queue ! videoconvert !

Using both tsparse and tsdemux seems redundant here. Just a note.

> xvimagesink
> 
> 
> 
> new receiver:
> 
> udpsrc adress=234.1.1.1 port=1234 caps="application/x-rtp,
> media=(string)video, clock-rate=(int)90000, payload=(int)96,
> encoding-name=(string)H264" ! rtph264depay ! avdec_h264 ! videoconvert !
> xvimagesink
> 
> 
> 
> --
> Sent from: http://gstreamer-devel.966125.n4.nabble.com/
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