Merge pull request #930 from ericrosenbaum/bugfix/loudness-performance

Only measure loudness once per step

src/blocks/scratch3_sensing.js

@@ -1,4 +1,5 @@
 const Cast = require('../util/cast');
+const Timer = require('../util/timer');
 
 class Scratch3SensingBlocks {
     constructor (runtime) {
@@ -14,6 +15,24 @@ class Scratch3SensingBlocks {
          */
         this._answer = '';
 
+        /**
+         * The timer utility.
+         * @type {Timer}
+         */
+        this._timer = new Timer();
+
+        /**
+         * The stored microphone loudness measurement.
+         * @type {number}
+         */
+        this._cachedLoudness = -1;
+
+        /**
+         * The time of the most recent microphone loudness measurement.
+         * @type {number}
+         */
+        this._cachedLoudnessTimestamp = 0;
+
         /**
          * The list of queued questions and respective `resolve` callbacks.
          * @type {!Array}
@@ -217,7 +236,17 @@ class Scratch3SensingBlocks {
 
     getLoudness () {
         if (typeof this.runtime.audioEngine === 'undefined') return -1;
-        return this.runtime.audioEngine.getLoudness();
+        if (this.runtime.currentStepTime === null) return -1;
+
+        // Only measure loudness once per step
+        const timeSinceLoudness = this._timer.time() - this._cachedLoudnessTimestamp;
+        if (timeSinceLoudness < this.runtime.currentStepTime) {
+            return this._cachedLoudness;
+        }
+
+        this._cachedLoudnessTimestamp = this._timer.time();
+        this._cachedLoudness = this.runtime.audioEngine.getLoudness();
+        return this._cachedLoudness;
     }
 
     getAttributeOf (args) {

test/unit/blocks_sensing.js

@@ -83,3 +83,43 @@ test('set drag mode', t => {
 
     t.end();
 });
+
+test('get loudness with caching', t => {
+    const rt = new Runtime();
+    const sensing = new Sensing(rt);
+
+    // It should report -1 when audio engine is not available.
+    t.strictEqual(sensing.getLoudness(), -1);
+
+    // Stub the audio engine with its getLoudness function, and set up different
+    // values to simulate it changing over time.
+    const firstLoudness = 1;
+    const secondLoudness = 2;
+    let simulatedLoudness = firstLoudness;
+    rt.audioEngine = {getLoudness: () => simulatedLoudness};
+
+    // It should report -1 when current step time is null.
+    t.strictEqual(sensing.getLoudness(), -1);
+
+    // Stub the current step time.
+    rt.currentStepTime = 1000 / 30;
+
+    // The first time it works, it should report the result from the stubbed audio engine.
+    t.strictEqual(sensing.getLoudness(), firstLoudness);
+
+    // Update the simulated loudness to a new value.
+    simulatedLoudness = secondLoudness;
+
+    // Simulate time passing by advancing the timer forward a little bit.
+    // After less than a step, it should still report cached loudness.
+    let simulatedTime = Date.now() + (rt.currentStepTime / 2);
+    sensing._timer = {time: () => simulatedTime};
+    t.strictEqual(sensing.getLoudness(), firstLoudness);
+
+    // Simulate more than a step passing. It should now request the value
+    // from the audio engine again.
+    simulatedTime += rt.currentStepTime;
+    t.strictEqual(sensing.getLoudness(), secondLoudness);
+
+    t.end();
+});