Large packet loss when estimated bandwidth is close to the lowest SVC layer

[vpalmisano]

Bug Report

When the estimated bandwidth is close to the lowest SVC layer, the allocated layer fluctuates between 0:0 and -1:-1. Concurrently, we observed large packet loss spikes at receiver side (80-100%) that didn't happen when using VP8/Simulcast in the same conditions. Analyzing the captured RTP packets, there are large seqno jumps that could explain the packet loss:

nopatch.pcapng.gz

The issue can be reproduced consuming 1 VP9 stream and calling transport.setMaxOutgoingBitrate(80000) (set a number close to the lowest encoded SVC layer).

[jmillan]

I plan to check this issue in the next days.

[jmillan]

It's been very complicate taking the time to check this lately. I can't say when I'm going to be able to check this.

Meson option ms_rtc_logger_rtp will print a log line for each RTP packet sent or dropped by mediasoup indicating the cause in case of drop, which would be a good way to troubleshot this. In case anyone is willing to dig further.

cd worker && MESON_ARGS="-Dms_rtc_logger_rtp=true" make