Occasionally no audio between webrtcbin and chrome

[Olivier Crête]

Hi,
To debug this, I would check a couple things:
1. If you look at the SDP, are all the payload types unique across all media?2. Using Wireshark, can you use audio RTP packets (you should be able to identify them by their payload type).3. If GStreamer is actually not sending anything, can you check with GST_DEBUG=*SCHED*:9 how far down the audio packets go? Ie where are they dropped? Or maybe some thread is blocked?
Olivier
On Mon, 2020-07-20 at 15:15 -0500, Trey Hutcheson wrote:
> Gstreamer 1.16.2; arch linux.
> 
> Ok, this one is really weird. I've got a media server (written in rust, if that matters) that juggles multiple gstreamer pipelines, with webrtc being the central use case. Occasionally when a browser based peer (google chrome) joins, it receives no audio.
> The pipeline is pretty basic; an audiotestsrc emits a test tone, encoding as opus, to webrtcbin. The browser side should simply pipe the audio to the local speaker. About 50% of the time, after signalling and ice connectivity has been established, there is no audio. In the cases when there is no audio, I've looked at chrome://webrtc-internals, and the audio track for the browser peer is not receiving any samples; no audio level, audio energy, etc. 
> 
> So I've tested a variety of scenarios. If I restart the browser between each test, there is no change. If I restart my media server between each iteration, then I receive audio 100% of the time. I added an identity element after `rtpopuspay` to dump the data to the console, and the data is definitely there. I monitored udp traffic with wireshark; the number and size of packets to the browser is roughly the same when there is audio and when there is not. 
> 
> So then I turned up gstreamer logging to see if it gave me any insight, and viola! I now have audio 100% of the time. When I set GST_DEBUG to 4 or higher, I get audio on every test iteration. Anything below 3, and the browser emits audio only occasionally. 
> 
> Does anyone have insight on what might be going on here?
> 
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-- 
Olivier Crête
olivier.crete at collabora.com

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