[Live-devel] redundant RTP stream setup question

[LANGLOIS Olivier PIS -EXT]

Hi,

I am working on a system having 2 redundant streamers. The slave streamer starts streaming when a failure is detected on the primary streamer. Players (VLC using live555 (v2014.05.27)) are notified of the change with SAP.

The problem is that for a very short period of time, there can be 2 different streams sent to the same multicast destination and this seems to make live555 to just close the stream instead of persisting trying to process RTP packets until the stream becomes clean.

I have quickly consulted rfc3550 and it appears to say that you should never have different streams sent at the same address. We will probably make sure that master and slave streams have different destinations even if most of the time there should not be both present simultaneously. I am reaching out the list just for seeking comments on my situation and also to check if it could be possible that live555 rtp client could eventually become more robust against this type of issue or if it is considered such a big misuse of RTP that is unlikely that this will never be looked at.

Here are VLC traces:

[0x8227190] main input debug: `sdp://v=0
o=- 22857 1 IN IP4 10.130.3.112
s=Stream Id 1
i=vspStreamer
c=IN IP4 239.10.10.50/255
t=0 0
a=type:broadcast
a=recvonly
m=video 6000 RTP/AVP 96
b=RR:0
a=rtpmap:96 H264/90000' successfully opened
[0x82da030] packetizer_h264 packetizer warning: waiting for SPS/PPS
[0x82da030] packetizer_h264 packetizer debug: found NAL_SPS (sps_id=0)
[0x82da030] packetizer_h264 packetizer debug: found NAL_PPS (pps_id=0 sps_id=0)
...
[0x821eb40] live555 demux debug: tk->rtpSource->hasBeenSynchronizedUsingRTCP()
[0x8227190] main input error: ES_OUT_RESET_PCR called
[0x8227190] main input warning: clock gap, unexpected stream discontinuity
[0x8227190] main input warning: feeding synchro with a new reference point trying to recover from clock gap
[0x821eb40] live555 demux debug: StreamClose
[0x8227190] main input debug: EOF reached
[0x8227190] main input debug: waiting decoder fifos to empty

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