first draft audio support

core/audio.js

@@ -0,0 +1,43 @@
+/*
+ * noVNC: HTML5 VNC client
+ * Copyright (C) 2020 The noVNC Authors
+ * Licensed under MPL 2.0 (see LICENSE.txt)
+ *
+ * See README.md for usage and integration instructions.
+ */
+
+export default class AudioBuffer {
+    constructor(codec) {
+        // instantiate a media source and audio buffer/queue
+        this._mediaSource = new MediaSource();
+        this._audioBuffer = null;
+        this._audioQ = [];
+
+        // create a hidden audio element
+        this._audio = document.createElement('audio');
+        this._audio.src = window.URL.createObjectURL(mediaSource);
+
+        // when data is queued, start playing
+        this._mediaSource.addEventListener('sourceopen', function(e) {
+            this._audio.play();
+            this._audioBuffer = mediaSource.addSourceBuffer(codec)
+            this._audioBuffer.addEventListener('update', function() {
+                if (this._audioQ.length > 0 && !this._audioBuffer.updating) {
+                    this._audioBuffer.appendBuffer(this._audioQ.shift())
+                }
+            })
+        }, false)
+    }
+
+    queueAudio(data) {
+        if (this._audioBuffer !== null) {
+            if (this._audioBuffer.updating || this._audioQ.length > 0) {
+                this._audioQ.push(data)
+            } else {
+                this._audioBuffer.appendBuffer(data)
+            }
+        }
+    }
+
+    close() {}  // intentionally left empty as no cleanup seems necessary
+}

core/rfb.js

@@ -499,6 +499,15 @@ export default class RFB extends EventTargetMixin {
         }
     }
 
+    enableAudio(sampleFormat, channels, frequency) {
+        RFB.messages.SetQEMUExtendedAudioFormat(this._sock, sampleFormat, channels, frequency)
+        RFB.messages.ToggleQEMUExtendedAudio(this._sock, true)
+    }
+
+    disableAudio() {
+        RFB.messages.ToggleQEMUExtendedAudio(this._sock, false)
+    }
+
     // ===== PRIVATE METHODS =====
 
     _connect() {
@@ -2039,6 +2048,25 @@ export default class RFB extends EventTargetMixin {
         return true;
     }
 
+    _handleQEMUExtAudioMsg() {
+        if (this._sock.rQwait("QEMU extended audio message", 3, 1)) { return false; }
+
+        this._sock.rQshift8(); // for now there is only a single submessage type 1
+        const operation = this._sock.rQshift16();
+
+        if (operation === 1) { // stream is starting
+            this._audioBuffer = new AudioBuffer('audio/webm; codecs="opus"') // TODO: This is obviously not the right value to use here
+        } else if (operation === 0) { // stream is stopping
+            this._audioBuffer.close()
+        } else {  // stream data
+            const length = this._sock.rQshift32();
+            const data = this._sock.rQshiftBytes(length);
+            this._audioBuffer.queueAudio(data)
+        }
+
+        return true;
+    }
+
     _handleXvpMsg() {
         if (this._sock.rQwait("XVP version and message", 3, 1)) { return false; }
         this._sock.rQskipBytes(1);  // Padding
@@ -2112,6 +2140,9 @@ export default class RFB extends EventTargetMixin {
 
             case 250:  // XVP
                 return this._handleXvpMsg();
+    
+            case 255: // Qemu extended audio message
+                return this._handleQEMUExtAudioMsg();
 
             default:
                 this._fail("Unexpected server message (type " + msgType + ")");
@@ -2549,6 +2580,16 @@ export default class RFB extends EventTargetMixin {
     }
 }
 
+// Audio sample formats
+RFB.sampleFormats = {
+    U8: 0,
+    S8: 1,
+    U16: 2,
+    S16: 3,
+    U32: 4,
+    S32: 5
+}
+
 // Class Methods
 RFB.messages = {
     keyEvent(sock, keysym, down) {
@@ -2570,6 +2611,48 @@ RFB.messages = {
         sock.flush();
     },
 
+    ToggleQEMUExtendedAudio(sock, enabled) {
+        const buff = sock._sQ;
+        const offset = sock._sQlen;
+
+        buff[offset] = 255;        // msg-type
+        buff[offset + 1] = 1;      // sub msg-type
+
+        buff[offset + 2] = 0;      // operation
+        if (enabled) {
+            buff[offset + 3] = 0;
+        } else {
+            buff[offset + 3] = 1;
+        }
+
+        sock._sQlen += 4;
+        sock.flush();
+    },
+
+    SetQEMUExtendedAudioFormat(sock, sampleFormat, channels, frequency) {
+        const buff = sock._sQ;
+        const offset = sock._sQlen;
+
+        buff[offset] = 255;     // msg type
+        buff[offset + 1] = 1;   // sub msg-type
+
+        buff[offset + 2] = 0;   // operation
+        buff[offset + 3] = 2;
+
+        buff[offset + 4] = sampleFormat;
+        buff[offset + 5] = channels;
+
+        const freq = toUnsigned32bit(frequency);
+
+        buff[offset + 6] = freq >> 24;
+        buff[offset + 7] = freq >> 16;
+        buff[offset + 8] = freq >> 8;
+        buff[offset + 9] = freq;
+
+        sock._sQlen += 10;
+        sock.flush()
+    },
+
     QEMUExtendedKeyEvent(sock, keysym, down, keycode) {
         function getRFBkeycode(xtScanCode) {
             const upperByte = (keycode >> 8);