Video (SDP) will only play if it is started after gstreamer sink or VLC is started

[Nicolas Dufresne]

Le vendredi 26 février 2021 à 07:05 -0600, msousa a écrit :
> Hi
> I am streaming sdp from a test board, this is my .sdp file
> 
> v=0
> o=IP4 10.0.0.1
> m=video 5500 RTP/AVP 96
> c=IN IP4 10.0.0.1
> s= 
> a=rtpmap:96 H264/90000
> 
> This displays fine if the video stream (it is a test pattern from a test
> brd) is started after the gstreamer receive line or VLC is started. If the
> stream is already going, gstreamer doesn't show anything or the VLC screen
> remains blank, whichever of the two are tried. The stream can run
> continuously.
> 
> This is my gstreamer receiving line:
> $ gst-launch-1.0 -e -v udpsrc port=5500 caps = "application/x-rtp,
> media=(string)video, clock-rate=(int)90000, encoding-name=(string)H264,
> payload=(int)96" ! rtph264depay ! decodebin ! videoconvert ! fpsdisplaysink
> sync=false
> 
> 
> If the stream is already started, there is no display.
> 
> This is the gstreamer broadcast line from the test brd:
> # gst-launch-1.0 -e videotestsrc ! video/x-raw, width=640, height=480,
> framerate =30/1 ! omxh264enc ! rtph264pay ! udpsink host=10.0.0.2 port=5500

I bet your OMX encoder is using open GOP by default, which means it only
produces key frame once. Try and setup the interval. Another change I would do
is "config-interval=-1", this way, if you encoder does not resent the headers,
rtph264pay will do that for you. You need both a keyframes and stream headers to
start from already running RTP H264 stream.

> 
> I use VLC as my proof-of-concept before attempting gstreamer, but in this
> case I thought I might be able to get it to work with gstreamer first, but
> no. Either way, neither of them work.
> 
> Any suggestions would be appreciated.
> Thanks...
> 
> 
> 
> --
> Sent from: http://gstreamer-devel.966125.n4.nabble.com/
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