Audio synchronization between individual RTP audio streams

[Vitaliy Lazarev]

We have a system with one RX pipeline that is running on RPi4 and listening
to several UDP sources with different ports, and near 10 individual TXs.
All of the devices are located in the same room. TXs are sending their own
RTP stream over Wi-Fi to RX simultaneously + RTCP with SR and SDES. And
after some time due to network connection issues and other factors, these
TX audio streams are running out of audio sync (from 100ms to 1s audio lag).
We found a similar issue, and it says that if there is no RTCP connection
between RX and TXs, there will be no synchronization. But this issue is
about hosts that are not located in the same physical space.
Is RTCP usage can help to prevent audio lag between individual RTP streams
(maybe feedback with RRs)? Can it be solved only using RX side with some
manipulations with pipeline elements (rtpbin NTP/RTCP sync options), RTP
timestamps, or something?
Is this even possible to get a several milliseconds synchronization between
many RTP audio streams, that are located physically in one room?

Example of RX pipeline part:
gst-launch-1.0 -vvv audiomixer name=mixer ! autoaudiosink \
rtpbin name=rtpbin latency=200  \
udpsrc port=12500 caps="application/x-rtp, media=(string)audio,
payload=(int)96, clock-rate=(int)48000, encoding-name=(string)OPUS,
channels=2" ! rtpbin.recv_rtp_sink_0 \
rtpbin. ! rtpopusdepay ! opusdec ! mixer. \
udpsrc port=12501 ! rtpbin.recv_rtcp_sink_0 \
udpsrc port=12502 caps="application/x-rtp, media=(string)audio,
payload=(int)96, clock-rate=(int)48000, encoding-name=(string)OPUS,
channels=2" ! rtpbin.recv_rtp_sink_1 \
rtpbin. ! rtpopusdepay ! opusdec ! mixer. \
udpsrc port=12503 ! rtpbin.recv_rtcp_sink_1
___
Thank you,

*Vitaliy Lazarev*
Software Engineer,
notAnotherOne <http://notanotherone.com/>

E-mail: vlazarev at notanotherone.com
T: +7 911 296-73-93

-- 
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