Add README.

Also fix help description from --receiveAudioTo.

README.md

@@ -0,0 +1,43 @@
+# minimal-webrtc-gstreamer
+
+GStreamer client for
+[minimal-webrtc][https://git.aweirdimagination.net/perelman/minimal-webrtc].
+Primarily intended for getting camera/microphone streams from a
+smartphone into arbitrary GStreamer pipelines, but should be useful
+generally as a GStreamer WebRTC example application.
+
+Example usage:
+```sh
+./minimal-webrtc-host.py --url "https://apps.aweirdimagination.net/camera/" --receiveAudio --receiveVideo any
+```
+Note that by default test video and audio patterns are sent.
+Use `--sendAudio false`/`--sendVideo false` to disable them.
+
+Running that command will output a URL both as text and as a QR code to
+give to the web browser to connect to.
+
+```
+usage: minimal-webrtc-host.py [-h] [--url URL] [--roomName ROOMNAME]
+                              [--sendAudio SENDAUDIO] [--sendVideo SENDVIDEO]
+                              [--receiveAudio] [--receiveVideo RECEIVEVIDEO]
+                              [--receiveAudioTo RECEIVEAUDIOTO]
+                              [--receiveVideoTo RECEIVEVIDEOTO]
+
+optional arguments:
+  -h, --help            show this help message and exit
+  --url URL             URL from minimal-webrtc
+  --roomName ROOMNAME   room name to host
+  --sendAudio SENDAUDIO
+                        GStreamer audio pipeline to send
+  --sendVideo SENDVIDEO
+                        GStreamer video pipeline to send
+  --receiveAudio        Enable receiving audio
+  --receiveVideo RECEIVEVIDEO
+                        Set video to receive ("screen", "environment",
+                        "facing", "true", "false")
+  --receiveAudioTo RECEIVEAUDIOTO
+                        "auto" or file path or device=DEVICE where DEVICE is a
+                        PulseAudio sink to send received audio to
+  --receiveVideoTo RECEIVEVIDEOTO
+                        "auto" or file path to send received video to
+```

minimal-webrtc-host.py

@@ -321,7 +321,9 @@ if __name__ == '__main__':
                         help='Set video to receive ("screen", '
                              + '"environment", "facing", "true", "false")')
     parser.add_argument('--receiveAudioTo', default=None,
-                        help='"auto" or file path to send received audio to')
+                        help='"auto" or file path or device=DEVICE '
+                             + 'where DEVICE is a PulseAudio sink '
+                             + 'to send received audio to ')
     parser.add_argument('--receiveVideoTo', default=None,
                         help='"auto" or file path to send received video to')
     args = parser.parse_args()