Bug 916285 - Make OscillatorNode handle negative frequencies. r=karlt

--HG-- extra : rebase_source : 8db864efa7d7fcfc02d6c66b8b0f050180968ac9
shellylin · Dec 2, 2014 · 9d479b3 · 9d479b3
1 parent dc3fa97
commit 9d479b3
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Showing 3 changed files with 56 additions and 5 deletions.
diff --git a/dom/media/webaudio/OscillatorNode.cpp b/dom/media/webaudio/OscillatorNode.cpp
@@ -142,8 +142,10 @@ class OscillatorNodeEngine : public AudioNodeEngine
   void IncrementPhase()
   {
     mPhase += mPhaseIncrement;
-    if (mPhase > mPhaseWrap) {
-      mPhase -= mPhaseWrap;
+    if (mPhase > 2 * M_PI) {
+      mPhase -= 2 * M_PI;
+    } else if (mPhase < -2 * M_PI) {
+      mPhase += 2 * M_PI;
     }
   }
 
@@ -171,11 +173,10 @@ class OscillatorNodeEngine : public AudioNodeEngine
       detune = mDetune.GetValueAtTime(ticks, count);
     }
 
-    float signalPeriod = mSource->SampleRate() / mFinalFrequency;
     mFinalFrequency = frequency * pow(2., detune / 1200.);
+    float signalPeriod = mSource->SampleRate() / mFinalFrequency;
     mRecomputeParameters = false;
 
-    mPhaseWrap = 2 * M_PI;
     mPhaseIncrement = 2 * M_PI / signalPeriod;
   }
 
@@ -367,7 +368,6 @@ class OscillatorNodeEngine : public AudioNodeEngine
   float mPhase;
   float mFinalFrequency;
   float mPhaseIncrement;
-  float mPhaseWrap;
   bool mRecomputeParameters;
   nsRefPtr<ThreadSharedFloatArrayBufferList> mCustom;
   uint32_t mCustomLength;

diff --git a/dom/media/webaudio/test/mochitest.ini b/dom/media/webaudio/test/mochitest.ini
@@ -126,6 +126,7 @@ skip-if = (toolkit == 'gonk' && !debug)
 [test_offlineDestinationChannelCountMore.html]
 [test_oscillatorNode.html]
 [test_oscillatorNode2.html]
+[test_oscillatorNodeNegativeFrequency.html]
 [test_oscillatorNodePassThrough.html]
 [test_oscillatorNodeStart.html]
 [test_oscillatorTypeChange.html]

diff --git a/dom/media/webaudio/test/test_oscillatorNodeNegativeFrequency.html b/dom/media/webaudio/test/test_oscillatorNodeNegativeFrequency.html
@@ -0,0 +1,50 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test the OscillatorNode when the frequency is negative</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="webaudio.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+addLoadEvent(function() {
+
+  var types = ["sine",
+               "square",
+               "sawtooth",
+               "triangle"];
+
+  var finished = 0;
+  function finish() {
+    if (++finished == types.length) {
+      SimpleTest.finish();
+    }
+  }
+
+  types.forEach(function(t) {
+    var context = new OfflineAudioContext(1, 256, 44100);
+    var osc = context.createOscillator();
+
+    osc.frequency.value = -440;
+    osc.type = t;
+
+    osc.connect(context.destination);
+    osc.start();
+    context.startRendering().then(function(buffer) {
+      var samples = buffer.getChannelData(0);
+      // This samples the wave form in the middle of the first period, the value
+      // should be negative.
+      ok(samples[Math.floor(44100 / 440 / 4)] < 0., "Phase should be inverted when using a " + t + " waveform");
+      finish();
+    });
+  });
+});
+
+</script>
+</pre>
+</body>
+</html>