Added dummy audio/video track if no media access

Signed-off-by: James Ketrenos <james_eikona@ketrenos.com>

client/src/MediaControl.js

@@ -392,6 +392,9 @@ const MediaAgent = ({setPeers}) => {
         * attach it to an <audio> or <video> tag if they give us access. */
       console.log("media-agent - Requesting access to local audio / video inputs");
   
+      /* See Dummy Tracks for more ideas...
+      https://blog.mozilla.org/webrtc/warm-up-with-replacetrack/
+      */
       navigator.getUserMedia = (navigator.getUserMedia ||
         navigator.webkitGetUserMedia ||
         navigator.mozGetUserMedia ||
@@ -399,15 +402,39 @@ const MediaAgent = ({setPeers}) => {
   
       return navigator.mediaDevices
       .getUserMedia({audio: true, video: true})
+      .then((media) => {
+        return {
+          media: media,
+          audio: true,
+          video: true
+        };
+      })
       .catch((error) => {
-        console.log(`media-agent - Access granted to audio and video ` +
+        console.log(`media-agent - Access to audio and video ` +
           `failed. Trying just audio.`);
         return navigator.mediaDevices
         .getUserMedia({ audio: true, video: false })
+        .then((media) => {
+          return {
+            media: media,
+            audio: true,
+            video: false
+          };
         })
-      .then((media) => { /* user accepted access to a/v */
+        .catch((error) => {
+          console.log(`media-agent - Access to audio ` +
+            `failed.`);
+          return {
+            media: undefined,
+            audio: false,
+            video: false
+          };
+        });
+      })
+      .then((context) => { /* user accepted access to a/v */
+        if (context.video) {
           console.log("media-agent - Access granted to audio/video");
-        media.getVideoTracks().forEach((track) => {
+          context.media.getVideoTracks().forEach((track) => {
             track.applyConstraints({
               "video": {
                 "width": {
@@ -421,8 +448,46 @@ const MediaAgent = ({setPeers}) => {
               }
             });
           });
+          return context.media;
+        }
 
-        return media;
+        const black = ({ width = 640, height = 480 } = {}) => {
+          const canvas = Object.assign(document.createElement("canvas"), {
+            width, height
+          });
+          canvas.getContext('2d').fillRect(0, 0, width, height);
+          const stream = canvas.captureStream();
+          return Object.assign(stream.getVideoTracks()[0], {
+            enabled: true
+          });
+        }
+
+        const silence = () => {
+          const ctx = new AudioContext(), oscillator = ctx.createOscillator();
+          const dst = oscillator.connect(ctx.createMediaStreamDestination());
+          oscillator.start();
+          return Object.assign(dst.stream.getAudioTracks()[0], {
+            enabled: true
+          });
+        }
+
+        if (context.audio) {
+          console.log("media-agent - Access granted to audio");
+
+          let black = ({ width = 640, height = 480 } = {}) => {
+            let canvas = Object.assign(document.createElement("canvas"), {
+              width, height
+            });
+            canvas.getContext('2d').fillRect(0, 0, width, height);
+            let stream = canvas.captureStream();
+            return Object.assign(stream.getVideoTracks()[0], {
+              enabled: true
+            });
+          }
+          return new MediaStream([context.media, black()]);
+        }
+
+        return new MediaStream([black(), silence()]);
       });
     };