Merge pull request #85 from mzgoddard/volume-effect

add and use VolumeEffect in AudioPlayer

src/AudioPlayer.js

@@ -1,5 +1,6 @@
-const PitchEffect = require('./effects/PitchEffect');
 const PanEffect = require('./effects/PanEffect');
+const PitchEffect = require('./effects/PitchEffect');
+const VolumeEffect = require('./effects/VolumeEffect');
 
 const SoundPlayer = require('./SoundPlayer');
 
@@ -17,9 +18,11 @@ class AudioPlayer {
         this.outputNode = this.audioEngine.audioContext.createGain();
 
         // Create the audio effects
-        const pitchEffect = new PitchEffect(this.audioEngine, this, null);
+        const volumeEffect = new VolumeEffect(this.audioEngine, this, null);
+        const pitchEffect = new PitchEffect(this.audioEngine, this, volumeEffect);
         const panEffect = new PanEffect(this.audioEngine, this, pitchEffect);
         this.effects = {
+            volume: volumeEffect,
             pitch: pitchEffect,
             pan: panEffect
         };
@@ -28,6 +31,7 @@ class AudioPlayer {
         // outputNode -> "pitchEffect" -> panEffect -> audioEngine.input
         panEffect.connect(this.audioEngine);
         pitchEffect.connect(panEffect);
+        volumeEffect.connect(pitchEffect);
 
         // reset effects to their default parameters
         this.clearEffects();
@@ -123,9 +127,6 @@ class AudioPlayer {
         for (const effectName in this.effects) {
             this.effects[effectName].clear();
         }
-
-        if (this.audioEngine === null) return;
-        this.outputNode.gain.setTargetAtTime(1.0, 0, this.audioEngine.DECAY_TIME);
     }
 
     /**
@@ -133,8 +134,7 @@ class AudioPlayer {
      * @param {number} value - the volume in range 0-100
      */
     setVolume (value) {
-        if (this.audioEngine === null) return;
-        this.outputNode.gain.setTargetAtTime(value / 100, 0, this.audioEngine.DECAY_TIME);
+        this.setEffect('volume', value);
     }
 
     /**
@@ -142,6 +142,7 @@ class AudioPlayer {
      * @param {object} target - target whose node to should be connected
      */
     connect (target) {
+        this.outputNode.disconnect();
         this.outputNode.connect(target.getInputNode());
     }
 
@@ -149,6 +150,7 @@ class AudioPlayer {
      * Clean up and disconnect audio nodes.
      */
     dispose () {
+        this.effects.volume.dispose();
         this.effects.pitch.dispose();
         this.effects.pan.dispose();
 

src/effects/Effect.js

@@ -38,7 +38,7 @@ class Effect {
      * @return {boolean} is the effect affecting the graph?
      */
     get _isPatch () {
-        return this.initialized;
+        return this.initialized && this.value !== this.DEFAULT_VALUE;
     }
 
     /**
@@ -46,7 +46,7 @@ class Effect {
      * @return {AudioNode} - audio node that is the input for this effect
      */
     getInputNode () {
-        if (this.initialized) {
+        if (this._isPatch) {
             return this.inputNode;
         }
         return this.target.getInputNode();
@@ -117,6 +117,10 @@ class Effect {
             return;
         }
 
+        if (this.outputNode !== null) {
+            this.outputNode.disconnect();
+        }
+
         let nextTarget = target;
         if (this._isPatch) {
             nextTarget = this;

src/effects/PanEffect.js

@@ -20,14 +20,6 @@ class PanEffect extends Effect {
         this.channelMerger = null;
     }
 
-    /**
-     * Should the effect be connected to the audio graph?
-     * @return {boolean} is the effect affecting the graph?
-     */
-    get _isPatch () {
-        return this.initialized && this.value !== 0;
-    }
-
     /**
      * Initialize the Effect.
      * Effects start out uninitialized. Then initialize when they are first set

src/effects/VolumeEffect.js

@@ -0,0 +1,54 @@
+const Effect = require('./Effect');
+
+/**
+ * Affect the volume of an effect chain.
+ */
+class VolumeEffect extends Effect {
+    /**
+     * Default value to set the Effect to when constructed and when clear'ed.
+     * @const {number}
+     */
+    get DEFAULT_VALUE () {
+        return 100;
+    }
+
+    /**
+     * Initialize the Effect.
+     * Effects start out uninitialized. Then initialize when they are first set
+     * with some value.
+     * @throws {Error} throws when left unimplemented
+     */
+    initialize () {
+        this.inputNode = this.audioEngine.audioContext.createGain();
+        this.outputNode = this.inputNode;
+
+        this.initialized = true;
+    }
+
+    /**
+     * Set the effects value.
+     * @private
+     * @param {number} value - new value to set effect to
+     */
+    _set (value) {
+        this.value = value;
+        // A gain of 1 is normal. Scale down scratch's volume value. Apply the
+        // change over a tiny period of time.
+        this.outputNode.gain.setTargetAtTime(value / 100, 0, this.audioEngine.DECAY_TIME);
+    }
+
+    /**
+     * Clean up and disconnect audio nodes.
+     */
+    dispose () {
+        this.outputNode.disconnect();
+
+        this.inputNode = null;
+        this.outputNode = null;
+        this.target = null;
+
+        this.initialized = false;
+    }
+}
+
+module.exports = VolumeEffect;