Pipeline stalling for no apparent reason?

[Florian Echtler]

Hello everyone,

I have a rather complex streaming pipeline that's constructed/managed from a 
Python script [1]. There are 2 (or more) clients that send MPEG transport 
streams over UDP to the pipeline, which then sends a "remixed" version of those 
streams back.

One issue I'm having now is that the pipeline works just as intended if the 
clients connect/start sending sequentially with 1-2 seconds of gap between, but 
if 2 or more clients already are sending when the pipeline launches, then it 
gets stuck in PAUSED state. (This started happening once I added the audio 
mixing branch to the pipeline.)

Weirdly enough, I checked the debug graph output and it seems to be 1:1 
identical, so exactly the same elements get created and linked in both cases 
(see attachments).

I already checked the output with GST_DEBUG=4 and couldn't find any concrete 
reason for why this happens. I assume it's some sort of race condition related 
to how the SSRC and transport stream demuxer pads get added, but I'm at a bit of 
a loss about how to debug this...

Any suggestions highly appreciated!

Best, Florian

[1] https://github.com/floe/surface-streams/blob/master/scripts/gst-mixer.py
-- 
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