WebRTC with data channel only?

[Matthew Waters]

Data channel only can work, but a lot of the data channel cases only
work with master at the moment.  Backporting some of the required
commits fixes to 1.16 is not easy.

e.g. here is a validate scenario that only opens a data channel and
sends some data:
https://gitlab.freedesktop.org/gstreamer/gst-examples/-/blob/master/webrtc/check/validate/scenarios/send_data_channel_string.scenario

On 18/7/20 12:09 am, William Gerecke wrote:
> I'm still having this problem first posted in March.  I'm using
> GStreamer webrtcbin to send data over a WebRTC data channel and all is
> working well!  The only problem is for the data channel to be
> established I also need to specify a dummy audio stream as follows:
>
> pipe1 = gst_parse_launch("webrtcbin  name=sendrecv "
>  "audiotestsrc is-live=true  ! audioconvert ! audioresample ! queue !
> opusenc  ! rtpopuspay ! "
>  "queue ! " RTP_CAPS_OPUS "97 ! sendrecv. ", &error);
>
> When I try webrtcbin by itself or with a fakesrc instead of an audio
> source I can still create the data channel as below without errors but
> I never get the "on-open" callback like I do when an audio source is
> present.
>
> g_signal_emit_by_name(webrtc1, "create-data-channel", "channel", NULL,
> &send_channel);
> if (send_channel) {
>   g_print("Created data channel\n");
>   connect_data_channel_signals(send_channel, session);
> }
>
> So in short - can webrtcbin be configured to work with only data
> channels, and if so, what am I missing?
>
> Bill
>
> On Tue, Mar 31, 2020 at 11:30 AM Bill G <foatus at hotmail.com
> <mailto:foatus at hotmail.com>> wrote:
>
>     Hello,
>
>     I'm trying to get a webrtcbin running which has data channels only
>     (i.e. no audio, no video.)  I started with the working sendrecv
>     example and got to the point where I had a working data-channel
>     with audio only.  When I remove audio the data channels fail to
>     connect - one data channel is created by GStreamer code, another
>     intiated on the browser side. 
>
>     I found and example (link below) for only receiving streams in
>     which the gst_parse_launch() was removed and one-way transceivers
>     manually added.  I read that without a audio/video sink pad
>     connected the transceivers need to be manually created.  Maybe
>     this is also related to data channels not functioning?
>
>     https://github.com/centricular/gstwebrtc-demos/compare/master...a-morales:figure-out-transceivers?expand=1
>
>     So, I'm assuming there is something preventing these data-channels
>     from getting established, and asking how to get past it?  This is
>     with everything running on one machine, Windows and GStreamer
>     1.16.  Thanks in advance!
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>
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