Make FEC and PLP non-default (#1372)

I considered it might be useful to have something exposed that allows the end-user to set these if they want, but our current code doesn't allow for that. It'll remain an internal feature for the time being.

src/client/voice/opus/BaseOpusEngine.js

@@ -1,20 +1,25 @@
 class BaseOpus {
-  constructor(player) {
-    this.player = player;
-
+  /**
+   * @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)
+   */
+  constructor(options = {}) {
     this.ctl = {
       FEC: 4012,
       PLP: 4014,
     };
+
+    this.options = options;
   }
 
   init() {
     try {
-      // Enable FEC (forward error correction)
-      this.setFEC(true);
+      // Set FEC (forward error correction)
+      if (this.options.fec) this.setFEC(this.options.fec);
 
-      // Set PLP (expected packet loss percentage) to 15%
-      this.setPLP(0.15);
+      // Set PLP (expected packet loss percentage)
+      if (this.options.plp) this.setPLP(this.options.plp);
     } catch (err) {
       // Opus engine likely has no support for libopus CTL
     }

src/client/voice/opus/OpusEngineList.js

@@ -5,9 +5,9 @@ const list = [
 
 let opusEngineFound;
 
-function fetch(Encoder) {
+function fetch(Encoder, engineOptions) {
   try {
-    return new Encoder();
+    return new Encoder(engineOptions);
   } catch (err) {
     return null;
   }
@@ -17,9 +17,9 @@ exports.add = encoder => {
   list.push(encoder);
 };
 
-exports.fetch = () => {
+exports.fetch = engineOptions => {
   for (const encoder of list) {
-    const fetched = fetch(encoder);
+    const fetched = fetch(encoder, engineOptions);
     if (fetched) return fetched;
   }
   return null;