rtp timestamping

asked 2020-05-28 10:14:07 +0000


I've been looking at a transport protocol (SRT) preserving RTP headers. RTP isn't a supported scheme for the sample app I'm using (srt-live-transmit) but I can define the chunk size and decode a transport stream after conversion to and back form SRT.

My setup is a server running the app taking in an RTP stream (defined as udp with a chunk size of 1328 to get the app to work) that's flipped into an SRT stream, send over a LAN to a receiving server running the app to flip it back to udp:// I can then use a transport stream analyser on the recieving server looking at rtp:// to decode the stream.

My input stream has 3 sequence errors in it which appear in the output stream but when comparing the packets I see that while the SSRC is the same, the sequence numbers and timestamps have changed.

Reading the RFC I have interpreted that the app is working as a 'translator' preserving the SSRC and the timestamps are different as they are derived from the sampling clock at the sender, which would be different when sending from srt-live-transmit to the transport stream analyser application.

I've not done much work with these protocols to this level of detail before. Could anyone help confirm or deny this please?



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