Single stream audio/video in Chrome WebRTC without ssrc tags

Question

Is single stream audio (or video) via Chrome's WebRTC possible when you strip a=ssrc lines from the SDP?

I have tried filtering out a=ssrc lines (with the code below), but single stream audio did not work. I tried also single stream video and renaming instead of removing lines with the same result. I modify both offer and answer SDPs. Interestingly, this filtering works when you try sending SDPs with both audio & video - audio (only) will work in such scenario. However I had issues with re-negotiation in such scenario in our app, so this is probably not a valid solution.

You can see minimum example with the single stream audio / video in this repo: https://github.com/Tev-work/webrtc-audio-demo .

If it is possible, can you please provide minimal example of code with working audio? Preferably using the repo above, what should the modifySdp function (in public/client.js ) do?

Currently it modifies sdp with this code:

sdp = sdp.replace(/a=ssrc/g, 'a=xssrc');
sdp = sdp.replace(/a=msid-semantic/g, 'a=xmsid-semantic');
sdp = sdp.replace(/a=mid/g, 'a=xmid');
sdp = sdp.replace(/a=group:BUNDLE/g, 'a=xgroup:BUNDLE');

If it is not possible, do you know whether such limitation has been officialy stated somewhere (please link it), or it just at some point became unworkable? It seems like it was working before (around M29, see comments here https://bugs.chromium.org/p/webrtc/issues/detail?id=1941 - no mention that this was not supposed to be working).

Motivation: We are sometimes sending SDPs via SIP PBXs, which sometimes filter out SSRC lines. Supporting multiple streams in such situations is obviously out of question (maybe with some server side hacking streams?), but supporting at least audio-only for such scenarios would be useful for us.

Answer 1

that should still be possible, even though there are some side-effects like (legacy) getStats not recognizing the stream, see (this bug)[ https://bugs.chromium.org/p/webrtc/issues/detail?id=3342] .

What you are attempting is to remove the a=ssrc lines before calling setLocalDescription. This is probably not going to work. If you want to simulate the scenario try removing them before calling setRemoteDescription with the SDP.