support audio

static/js/grab-canvas.js

@@ -46,6 +46,16 @@
         throw new Error("Element don't habe video track")
     }
 
+    const canvasAudioTracks = canvasStream.getAudioTracks()
+    if(canvasAudioTracks.length > 0){
+        const AudioContext = window.AudioContext || window.webkitAudioContext;
+        if(AudioContext){
+            const audioContext = new AudioContext();
+            audioContext.createMediaStreamTrackSource(canvasAudioTracks[0])
+                .connect(audioContext.destination)
+        }
+    }
+
     const offer = await conn.createOffer();
     await conn.setLocalDescription(offer);