The format is {'sdp': {'sdp': <sdp>, 'type': <sdptype>}} The multiparty-sendrecv demo already uses this format.
JS code runs on the browser and uses the browser's webrtc implementation. C code uses gstreamer's webrtc implementation, for which you need the following repositories: https://github.com/ystreet/gstreamer/tree/promise https://github.com/ystreet/gst-plugins-bad/tree/webrtc You can build these with either Autotools gst-uninstalled: https://arunraghavan.net/2014/07/quick-start-guide-to-gst-uninstalled-1-x/ Or with Meson gst-build: https://cgit.freedesktop.org/gstreamer/gst-build/