Audio bitrate support (#1439)

* Audio bitrate support

Note: not implemented for VoiceBroadcasts

* Fix default args, auto bitrate

* Late night typos are the best

* Changes bitrate to kbps for VoiceChannel stuff

* Add methods to manipulate bitrate while encoding

src/client/voice/opus/BaseOpusEngine.js

@@ -4,21 +4,38 @@
  */
 class BaseOpus {
   /**
-   * @param {Object} [options] The options to apply to the Opus engine
-   * @param {boolean} [options.fec] Whether to enable forward error correction (defaults to false)
-   * @param {number} [options.plp] The expected packet loss percentage (0-1 inclusive, defaults to 0)
+   * @param {Object} [options] The options to apply to the Opus engine.
+   * @param {number} [options.bitrate=48] The desired bitrate (kbps).
+   * @param {boolean} [options.fec=false] Whether to enable forward error correction.
+   * @param {number} [options.plp=0] The expected packet loss percentage.
    */
-  constructor(options = {}) {
+  constructor({ bitrate = 48, fec = false, plp = 0 } = {}) {
     this.ctl = {
+      BITRATE: 4002,
       FEC: 4012,
       PLP: 4014,
     };
 
-    this.options = options;
+    this.samplingRate = 48000;
+    this.channels = 2;
+
+    /**
+     * The desired bitrate (kbps)
+     * @type {number}
+     */
+    this.bitrate = bitrate;
+
+    /**
+     * Miscellaneous Opus options
+     * @type {Object}
+     */
+    this.options = { fec, plp };
   }
 
   init() {
     try {
+      this.setBitrate(this.bitrate);
+
       // Set FEC (forward error correction)
       if (this.options.fec) this.setFEC(this.options.fec);
 

src/client/voice/opus/NodeOpusEngine.js

@@ -10,10 +10,14 @@ class NodeOpusEngine extends OpusEngine {
     } catch (err) {
       throw err;
     }
-    this.encoder = new opus.OpusEncoder(48000, 2);
+    this.encoder = new opus.OpusEncoder(this.samplingRate, this.channels);
     super.init();
   }
 
+  setBitrate(bitrate) {
+    this.encoder.applyEncoderCTL(this.ctl.BITRATE, Math.min(128, Math.max(16, bitrate)) * 1000);
+  }
+
   setFEC(enabled) {
     this.encoder.applyEncoderCTL(this.ctl.FEC, enabled ? 1 : 0);
   }

src/client/voice/opus/OpusEngineList.js

@@ -5,8 +5,6 @@ const list = [
   require('./OpusScriptEngine'),
 ];
 
-let opusEngineFound;
-
 function fetch(Encoder, engineOptions) {
   try {
     return new Encoder(engineOptions);
@@ -27,10 +25,6 @@ exports.fetch = engineOptions => {
     const fetched = fetch(encoder, engineOptions);
     if (fetched) return fetched;
   }
-  return null;
-};
 
-exports.guaranteeOpusEngine = () => {
-  if (typeof opusEngineFound === 'undefined') opusEngineFound = Boolean(exports.fetch());
-  if (!opusEngineFound) throw new Error('OPUS_ENGINE_MISSING');
+  throw new Error('OPUS_ENGINE_MISSING');
 };

src/client/voice/opus/OpusScriptEngine.js

@@ -10,10 +10,14 @@ class OpusScriptEngine extends OpusEngine {
     } catch (err) {
       throw err;
     }
-    this.encoder = new OpusScript(48000, 2);
+    this.encoder = new OpusScript(this.samplingRate, this.channels);
     super.init();
   }
 
+  setBitrate(bitrate) {
+    this.encoder.encoderCTL(this.ctl.BITRATE, Math.min(128, Math.max(16, bitrate)) * 1000);
+  }
+
   setFEC(enabled) {
     this.encoder.encoderCTL(this.ctl.FEC, enabled ? 1 : 0);
   }