[Bug 797280] webrtcbin: video pixelated

[GStreamer (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=797280

--- Comment #19 from Dmitriy <degtyaryov at gmail.com> ---
I was on vacation, so it was not possible to experiment.

I tried to configure the linux kernel, but that did not change anything.

Made more convenient output of data on packet loss from get-stats.

Video pixelated immediately after the first loss. Next, the packet lost counter
increases by about 100 per second. This goes on for a few minutes. Then the
video is restored and the packet lost counter stops increasing. After a few
seconds, everything repeats.

Changing net.core.rmem_max gives nothing.
sysctl -w net.core.rmem_max=16777216

I compared the data from the get-stats with the data from /proc/net/udp.

# cat /proc/net/udp | grep ':DDED'
  sl  local_address rem_address   st tx_queue rx_queue tr tm->when retrnsmt  
uid  timeout inode ref pointer drops
 1060: 8201A8C0:DDED 00000000:0000 07 00000000:00000000 00:00000000 00000000 
1000        0 1202334542 2 000000009ee2ba36 10603

>From get-stats:
Inbound RTP Stats:
        ssrc: 1183057958
        fir-count: 0
        pli-count: 0
        nack-count: 0
        packets-received: 791085
        bytes-received: 917999656
        jitter: 1
        packets-lost: 98057


/proc/net/udp in 10 times less. Packet lost counter increases by about 100 per
second, but value drops in /proc/net/udp changes extremely rarely, no
correlation.

All of the above said about CPU Intel Core i5-2300 and chrome <-> gstreamer
without vaapi.
On CPU Intel Core i7-7500U in /proc/net/udp always 0, but after ~10 minute
video pixelated, get-stats show packets-lost ~ 100 in sec and /proc/net/udp
everything is 0.

Why ~20 sec no packet drops and then packet lost regularly?

The chrome graphics show that it does not send huge frames. Nack PLI not
working. Why decodebin not send event GstForceKeyUnit?
How to make it work?

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