[Freeswitch-dev] Question about RTP marker

Peter Olsson peter.olsson at visionutveckling.se
Tue Jul 3 18:39:53 MSD 2012

When I've been debugging RTP streams in Wireshark, I've noticed that Whireshark will get "everything wrong" when the timestamp changes (is reset). For instance, if I call a conference, by the time I get into the conference, the RTP timestamps will start over, and FS will send the marker bit By that time Wireshark will report strange figures for jitter etc.

After some Googling I've found that the meaning of the RTP marker is to indicate "the beginning of a talkspurt". Which is not very clear to me... :)

So my question is - is RTP marker really enough when starting a "new RTP stream" (not really new, but since the timestamps are reset we can think of it like that) - according to what I've been able to find, maybe the SSRC should also be changed?

I have created a patch that will change the SSRC when a reset like this occurs, and after that Wireshark detects my audio streams without problems (though, it will detect more streams), but no strange jitter figures etc. are reported.

The reason I started digging into this was because a PBX I was connecting to lost about the first second of audio after connecting to the conference, after also changing the SSRC the problem seems resolved.

I could make a RTP_BUG setting for this, but I'm not really sure if I should really care - that's why I'm asking here, if anyone has more knowledge about this?


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