Webrtc audio

[Anthony Williams]

Hi,

We're trying to use webrtc for dynamic audio and video streams: we open
the webrtc connection and set up a data channel, then use that data
channel to request audio and video streams. We've currently got a video
stream working, but the audio stream is proving tricky.

The audio pipeline looks like this:

appsrc ! queue ! audioconvert ! audioresample ! queue ! opusenc !
rtpopuspay ! queue !
application/x-rtp,media=audio,encoding-name=OPUS,payload=97 ! sendrecv

Where sendrecv is the webrtcbin element.

The SDP sent to the browser looks like this:

v=0
o=- 9184785277063451528 0 IN IP4 0.0.0.0
s=-
t=0 0
a=ice-options:trickle
a=group:BUNDLE 0 audio0
m=application 9 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP4 0.0.0.0
a=setup:actpass
a=ice-ufrag:JISE4Q+H0eGZSMIaKcxpnnxXONQuXFHs
a=ice-pwd:UqqhM6p1eM0A6tlZh4mt2UQfdbjLEBz3
a=mid:0
a=sctp-port:5000
a=fingerprint:sha-256
D4:AF:66:6A:1E:C1:A6:35:14:D4:6D:CA:1F:71:F3:7E:90:19:E6:E8:30:CC:44:A5:31:BF:31:02:D0:71:8F:8B
m=audio 0 UDP/TLS/RTP/SAVPF 97
c=IN IP4 0.0.0.0
a=setup:actpass
a=ice-ufrag:JISE4Q+H0eGZSMIaKcxpnnxXONQuXFHs
a=ice-pwd:UqqhM6p1eM0A6tlZh4mt2UQfdbjLEBz3
a=bundle-only
a=rtcp-mux
a=rtcp-rsize
a=sendrecv
a=rtpmap:97 OPUS/48000
a=rtcp-fb:97 transport-cc
a=mid:audio0
a=fingerprint:sha-256
D4:AF:66:6A:1E:C1:A6:35:14:D4:6D:CA:1F:71:F3:7E:90:19:E6:E8:30:CC:44:A5:31:BF:31:02:D0:71:8F:8B

The browser then complains:

[1572:0520/090746.806032:ERROR:peer_connection.cc(6044)] Failed to set
remote audio description send parameters. (INVALID_PARAMETER)
[1572:0520/090746.806069:ERROR:peer_connection.cc(3054)] Failed to set
remote offer sdp: Failed to set remote audio description send parameters.
[1572:0520/090746.806146:ERROR:audio_rtp_receiver.cc(89)]
AudioRtpReceiver::OnSetVolume: No audio channel exists.
[1572:0520/090746.806218:ERROR:peer_connection.cc(2391)] CreateAnswer:
Session error code: ERROR_CONTENT. Session error description: Failed to
set remote audio description send parameters..

and the negotiation fails.

Has anyone seen anything like this before? Any ideas on what the problem
may be?

Thanks,

Anthony