WebRTC seems broken in the latest stable ( 66.0.3359.139 )

[Carlos Rafael Giani]

I was trying out the new GStreamer WebRTC support with Chrome using the
example attached here: https://bugzilla.gnome.org/show_bug.cgi?id=795404

This used to work nicely. Then Chrome got updated, and it is broken now.
It seems to be related to the local SDP generation, which for unknown
reasons does not add media information (fmtp, codecs etc.)


The offered SDP was:

v=0
o=- 6737774140683290487 0 IN IP4 0.0.0.0
s=-
t=0 0
a=ice-options:trickle
m=video 9 UDP/TLS/RTP/SAVPF 96
c=IN IP4 0.0.0.0
a=setup:actpass
a=ice-ufrag:OV0FuLpDqfaRlh+R5b8MdSxkWY71MvP/
a=ice-pwd:QXu78KE3un/AKg/qHYK5QuOYjELjrq+x
a=sendrecv
a=rtcp-mux
a=rtcp-rsize
a=rtpmap:96 H264/90000
a=rtcp-fb:96 nack
a=rtcp-fb:96 nack pli
a=mid:video0
a=fingerprint:sha-256
C5:7E:81:04:B9:94:AA:18:19:B0:AD:E3:60:DE:0C:96:EE:3F:87:7D:CD:DA:F6:15:4E:DA:6A:EB:4E:EC:22:2C
a=fmtp:96 profile-level-id=42c029

The answer is:

v=0
o=- 994571196877641501 2 IN IP4 127.0.0.1
s=-
t=0 0
a=msid-semantic: WMS
m=video 9 UDP/TLS/RTP/SAVPF 0
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:EoFM
a=ice-pwd:5Tras0Gz0etpkQ/mmxzqnwpc
a=ice-options:trickle
a=fingerprint:sha-256
43:51:00:13:B1:27:8B:76:30:A4:78:04:0C:4E:51:23:69:91:B2:D2:E7:D6:64:C0:AA:20:36:93:47:13:AB:7F
a=setup:active
a=mid:video0
a=recvonly
a=rtcp-mux
a=rtcp-rsize

See? No rtpmap, no rtcp-fb etc.

Is this a known bug in the newest stable?

[Taylor Brandstetter]

We only support a "packetization mode" of 1, and the packetization-mode parameter defaults to 0, so the H264 format isn't accepted. It will work if you add "packetization-mode=1" to the fmtp line.

The behavior changed in M66 since we started taking packetization mode into account when negotiating codecs.

hta/magjed: Based on this bug, it sounds like the work is actually done to support packetization mode 0, but it's not being negotiated in SDP yet? Any reason why?

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[Carlos Rafael Giani]

Indeed, with packetization-mode=1 it works! What is odd though that I have version 66.0.3359.126 on the Android phone, it used to work there too, but even with packetization-mode=1, it does not work anymore. I'll try to get some logs from there.

[Harald Alvestrand]

When I left this in March, I had finished the setting of packetization mode 0 for the OpenH264 codec, but I hadn't done the wiring to connect this to the SDP negotiation.

I suppose it fell between some cracks.

[Carlos Rafael Giani]

Since I wrote this email, considerable amount of work has been done to enhance the GStreamer WebRTC support. It now works fine with Chrome and Firefox on desktop. However, Chrome on my Samsung S8 refuses to work with h.264 and a WebRTC stream coming from GStreamer.

Relevant GStreamer bug reports:

https://bugzilla.gnome.org/show_bug.cgi?id=795404
https://bugzilla.gnome.org/show_bug.cgi?id=795044

The version of Chrome on my S8 is 67.0.3396.87.

Are there known issues with WebRTC and Chrome 67 on Android 8?

On 2018-05-02 19:43, Taylor Brandstetter wrote: