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81 lines
2.1 KiB
Markdown
81 lines
2.1 KiB
Markdown
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# Terminology
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### Client
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A GStreamer-based application
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### Browser
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A JS application that runs in the browser and uses built-in browser webrtc APIs
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### Peer
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Any webrtc-using application that can participate in a call
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### Signalling server
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Basic websockets server implemented in Python that manages the peers list and shovels data between peers
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# Overview
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This is a basic protocol for doing 1-1 audio+video calls between a gstreamer app and a JS app in a browser.
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# Peer registration and calling
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Peers must register with the signalling server before a call can be initiated. The server connection should stay open as long as the peer is available or in a call.
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This protocol builds upon https://github.com/shanet/WebRTC-Example/
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* Connect to the websocket server
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* Send `HELLO <uid>` where `<uid>` is a string which will uniquely identify this peer
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* Receive `HELLO`
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* Any other message starting with `ERROR` is an error.
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* To connect to a peer, send `SESSION <uid>` where `<uid>` identifies the peer to connect to, and receive `SESSION_OK`
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* All further messages will be forwarded to the peer
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* The call negotiation with the peer can be started by sending JSON encoded SDP and ICE
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* Closure of the server connection means the call has ended; either because the other peer ended it or went away
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* To end the call, disconnect from the server. You may reconnect again whenever you wish.
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# Negotiation
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Once a call has been setup with the signalling server, the peers must negotiate SDP and ICE candidates with each other.
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The calling side must create an SDP offer and send it to the peer as a JSON object:
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```json
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{
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"sdp": {
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"sdp": "o=- [....]",
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"type": "offer"
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}
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}
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```
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The callee must then reply with an answer:
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```json
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{
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"sdp": {
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"sdp": "o=- [....]",
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"type": "answer"
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}
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}
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```
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ICE candidates must be exchanged similarly by exchanging JSON objects:
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```json
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{
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"ice": {
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"candidate": ...,
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"sdpMLineIndex": ...,
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...
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}
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}
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```
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Note that the structure of these is the same as that specified by the WebRTC spec.
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