Complete mp3 web worker

js/SoundManager.js

@@ -54,7 +54,6 @@ function SoundManager(core) {
     this.maxBinLin = 0;
 
     // For concatenating our files
-    this.leftToLoad = 0;
     this.tmpBuffer = null;
     this.tmpBuild = null;
     this.onLoadCallback = null;
@@ -76,11 +75,7 @@ function SoundManager(core) {
     }
     
     this.mp3Worker = new Worker(core.settings.defaults.mp3WorkerPath + 'mp3-worker.js');
-    this.mp3Worker.addEventListener('message', function(e) {
-      console.log('Worker said: ', e.data);
-    }, false);
-    
-    this.mp3Worker.postMessage("Hello world");
+    this.mp3Worker.addEventListener('message', this.workerFinished.bind(this), false);
 
     window.addEventListener('touchend', function() {
         // create empty buffer
@@ -201,23 +196,73 @@ SoundManager.prototype.loadBuffer = function(song, callback) {
     if(callback) {
         this.onLoadCallback = callback;
     }
+    if(song.sound.byteLength == 0) {
+        // Someone went forward then immediately back then forward again
+        // Either way, the sound is still loading. It'll come back when it's ready
+        return;
+    }
+    var transferrables = [song.sound];
     if(song.buildup) {
-        this.loadAudioFile(song, true);
+        transferrables.push(song.buildup);
     }
-    this.loadAudioFile(song, false);
+    this.mp3Worker.postMessage(song, transferrables);
 };
 
-SoundManager.prototype.loadAudioFile = function(song, isBuild) {
-    var asset = AV.Asset.fromBuffer(isBuild ? song.buildup : song.sound);
-    asset.on("error", function(err) {
-        console.log(err);
-    });
-    asset.decodeToBuffer(function(buffer) {
-        console.log(asset.format);
-        console.log(buffer.length);
-        var channels = asset.format.channelsPerFrame;
+SoundManager.prototype.workerFinished = function(event) {
+    var result = event.data;
+    
+    // restore our old ArrayBuffers TODO race
+    var song = this.restoreBuffers(result.song);
+    
+    // Something else started loading after we started
+    if(this.song != song) {
+        console.log("Song changed before we could play it, user is impatient!");
+        return;
+    }
+
+    if(song.buildup) {
+        this.tmpBuild = this.trimMP3(this.audioBufFromRaw(result.build), song.forceTrim, song.noTrim);
+    }
+    this.tmpBuffer = this.trimMP3(this.audioBufFromRaw(result.loop), song.forceTrim, song.noTrim);
+    this.onSongLoad(song);
+}
+
+// We pass our ArrayBuffers away, so we need to put them back
+// We must iterate all the songs in case the player has moved on in the meantime
+ SoundManager.prototype.restoreBuffers = function(newSong) {
+     var songs = this.core.resourceManager.allSongs;
+     for(var i = 0; i < songs.length; i++) {
+         var oldSong = songs[i];
+         var same = true;
+         for(var attr in oldSong) {
+            if(oldSong.hasOwnProperty(attr) && attr != "buildup" && attr != "sound") {
+                var oldV = oldSong[attr];
+                var newV = newSong[attr];
+                if(oldV != newV) {
+                    // Equality checks break for NaN, and isNaN coerces args to Number, which we don't want
+                    if(!( (oldV != oldV) && (newV != newV) )) {
+                        same = false;
+                        break;
+                    }
+                }
+            }
+         }
+         if(same) {
+             oldSong.sound = newSong.sound;
+             oldSong.buildup = newSong.buildup;
+             return oldSong;
+         }
+     }
+     console.log("Oh no! Original song has been lost!");
+     return null;
+ }
+
+// Converts interleaved PCM to Web Audio API friendly format
+SoundManager.prototype.audioBufFromRaw = function(sound) {
+    var buffer = sound.array;
+    var channels = sound.channels;
     var samples = buffer.length/channels;
-        var audioBuf = this.context.createBuffer(channels, samples, asset.format.sampleRate);
+    var audioBuf = this.context.createBuffer(channels, samples, sound.sampleRate);
     var audioChans = [];
     for(var i = 0; i < channels; i++) {
         audioChans.push(audioBuf.getChannelData(i));
@@ -225,38 +270,10 @@ SoundManager.prototype.loadAudioFile = function(song, isBuild) {
     for(var i = 0; i < buffer.length; i++) {
         audioChans[i % channels][Math.round(i/channels)] = buffer[i];
     }
-        (this.getAudioCallback(song, isBuild))(audioBuf);
-    }.bind(this));
-};
-
-/* decodeAudioData nukes our original MP3 array, but we want to keep it around
-  for memory saving purposes, so we must duplicate it locally here */
-SoundManager.prototype.getAudioCallback = function(song, isBuild) {
-    var current = isBuild ? song.buildup : song.sound;
-    var copy = current.slice(0);
-    return function(buffer) {
-        // before the race condition check or we might lose data
-        if(isBuild) {
-            song.buildup = copy;
-        } else {
-            song.sound = copy;
-        }
-        // race condition prevention
-        if(this.song != song) {
-            return;
-        }
-        if(isBuild) {
-            this.tmpBuild = this.trimMP3(buffer, song.forceTrim, song.noTrim);
-        } else {
-            this.tmpBuffer = this.trimMP3(buffer, song.forceTrim, song.noTrim);
-        }
-        this.onSongLoad(song);
-    }.bind(this);
-};
+    return audioBuf;
+}
 
 SoundManager.prototype.onSongLoad = function(song) {
-    // if this fails, we need to wait for the other part to load
-    if(this.tmpBuffer && (!song.buildup || this.tmpBuild)) {
     if(song.buildup) {
         this.buffer = this.concatenateAudioBuffers(this.tmpBuild, this.tmpBuffer);
         this.loopStart = this.tmpBuild.duration;
@@ -271,7 +288,6 @@ SoundManager.prototype.onSongLoad = function(song) {
         this.onLoadCallback();
         this.onLoadCallback = null;
     }
-    }
 };
 
 // because MP3 is bad, we nuke silence

js/mp3/mp3-worker.js

@@ -1,5 +1,50 @@
 importScripts('aurora.js', 'mp3.js');
 
+var decodeBuffer = function(source, callback) {
+    var asset = AV.Asset.fromBuffer(source);
+    asset.on("error", function(err) {
+        console.log(err);
+    });
+    
+    asset.decodeToBuffer(function(buffer) {
+        var result = {array: buffer,
+                      sampleRate: asset.format.sampleRate,
+                      channels: asset.format.channelsPerFrame}
+        callback(result);
+    });
+}
+
+var finish = function(result, transferrables) {
+    transferrables.push(result.loop.array.buffer);
+    if(result.song.buildup) {
+        transferrables.push(result.build.array.buffer);
+        transferrables.push(result.song.buildup);
+    }
+    self.postMessage(result, transferrables);
+}
+
 self.addEventListener('message', function(e) {
-  self.postMessage(e.data);
+    var song = e.data;
+    
+    var result = {song: song, build: null, loop: null};
+    var transferrables = [result.song.sound];
+    
+    if(song.buildup) {
+        decodeBuffer(song.buildup, function(sound) {
+            result.build = sound;
+            // Song is finished too
+            if(result.loop) {
+                finish(result, transferrables);
+            }
+        });
+    }
+    
+    decodeBuffer(song.sound, function(sound) {
+        result.loop = sound;
+        // Either there was no build, or it's already loaded
+        if(!song.buildup || (song.buildup && result.build)) {
+            finish(result, transferrables);
+        }
+    });
+
 }, false);