[Live-devel] RTSP Server grey frames

[Ross Finlayson]

> We try to use live555 testOnDemandRTSPServer example with some modification to stream "low-latency" live video together with hardware HEVC encoder. Almost everything works fine inside the local network and we are able to playback video via VLC player. However, our goal is to transmit video over mobile network (4G/LTE) which is not always one hundred percent stable. According to measurements there is about 0,01% dropped frames from all requested frames by using RTP over UDP protocol.

Congratulations.  That’s a remarkably low packet loss rate.


> We try to find a cause and solution how to minimize/eliminate corrupted grey frames inside the video

I recommend that you reconfigure your encoder so that each key frame is encoded as a sequence of ’slice’ NAL units, rather than as a single NAL unit.

People often have trouble streaming H.264/H.265 video with extremely large key frames, if each key frame gets encoded as a single NAL-unit.  The problem with this is that these NAL units get sent as a (very long) sequence of RTP packets - and if even one of these RTP packets gets lost, then the whole NAL (key frame in this case) will get discarded by the receiver; see
	http://lists.live555.com/pipermail/live-devel/2011-December/014190.html
	http://lists.live555.com/pipermail/live-devel/2012-August/015615.html
	http://lists.live555.com/pipermail/live-devel/2013-May/016994.html
	http://lists.live555.com/pipermail/live-devel/2014-June/018426.html
	http://lists.live555.com/pipermail/live-devel/2014-June/018432.html
	http://lists.live555.com/pipermail/live-devel/2014-June/018433.html
	http://lists.live555.com/pipermail/live-devel/2014-June/018434.html
	http://lists.live555.com/pipermail/live-devel/2015-March/019135.html
	http://lists.live555.com/pipermail/live-devel/2015-April/019228.html
For streaming, it’s better to encode large key frames as a sequence of ‘slice’ NAL units.

Ross Finlayson
Live Networks, Inc.
http://www.live555.com/