From 04017096ddbbf1f93862f0832594eee4e4197020 Mon Sep 17 00:00:00 2001
From: Karl Tomlinson <karlt+@karlt.net>
Date: Fri, 25 Oct 2013 14:05:43 +1300
Subject: [PATCH] b=898291 skip HRTF panner processing when input has been null
 long enough for output to be null r=ehsan

--HG--
extra : transplant_source : %E4l%83zo%0E%08%14%FF%F7%9D%D6%8C%FD%A2%07a%2A%8Aq
---
 content/media/webaudio/PannerNode.cpp       | 37 ++++++++++++++++++---
 content/media/webaudio/blink/HRTFPanner.cpp | 21 +++++-------
 content/media/webaudio/blink/HRTFPanner.h   |  3 +-
 3 files changed, 42 insertions(+), 19 deletions(-)

diff --git a/content/media/webaudio/PannerNode.cpp b/content/media/webaudio/PannerNode.cpp
index 40a99e8af29..2d56af0fa4c 100644
--- a/content/media/webaudio/PannerNode.cpp
+++ b/content/media/webaudio/PannerNode.cpp
@@ -9,6 +9,7 @@
 #include "AudioNodeStream.h"
 #include "AudioListener.h"
 #include "AudioBufferSourceNode.h"
+#include "PlayingRefChangeHandler.h"
 #include "blink/HRTFPanner.h"
 #include "blink/HRTFDatabaseLoader.h"
 
@@ -58,6 +59,7 @@ public:
     // to some dummy values here.
     , mListenerDopplerFactor(0.)
     , mListenerSpeedOfSound(0.)
+    , mLeftOverData(INT_MIN)
   {
     // HRTFDatabaseLoader needs to be fetched on the main thread.
     TemporaryRef<HRTFDatabaseLoader> loader =
@@ -136,6 +138,35 @@ public:
                                  AudioChunk* aOutput,
                                  bool *aFinished) MOZ_OVERRIDE
   {
+    if (aInput.IsNull()) {
+      // mLeftOverData != INT_MIN means that the panning model was HRTF and a
+      // tail-time reference was added.  Even if the model is now equalpower,
+      // the reference will need to be removed.
+      if (mLeftOverData > 0) {
+        mLeftOverData -= WEBAUDIO_BLOCK_SIZE;
+      } else {
+        if (mLeftOverData != INT_MIN) {
+          mLeftOverData = INT_MIN;
+          mHRTFPanner->reset();
+
+          nsRefPtr<PlayingRefChangeHandler> refchanged =
+            new PlayingRefChangeHandler(aStream, PlayingRefChangeHandler::RELEASE);
+          aStream->Graph()->
+            DispatchToMainThreadAfterStreamStateUpdate(refchanged.forget());
+        }
+        *aOutput = aInput;
+        return;
+      }
+    } else if (mPanningModelFunction == &PannerNodeEngine::HRTFPanningFunction) {
+      if (mLeftOverData == INT_MIN) {
+        nsRefPtr<PlayingRefChangeHandler> refchanged =
+          new PlayingRefChangeHandler(aStream, PlayingRefChangeHandler::ADDREF);
+        aStream->Graph()->
+          DispatchToMainThreadAfterStreamStateUpdate(refchanged.forget());
+      }
+      mLeftOverData = mHRTFPanner->maxTailFrames();
+    }
+
     (this->*mPanningModelFunction)(aInput, aOutput);
   }
 
@@ -177,6 +208,7 @@ public:
   ThreeDPoint mListenerVelocity;
   double mListenerDopplerFactor;
   double mListenerSpeedOfSound;
+  int mLeftOverData;
 };
 
 PannerNode::PannerNode(AudioContext* aContext)
@@ -277,11 +309,6 @@ void
 PannerNodeEngine::EqualPowerPanningFunction(const AudioChunk& aInput,
                                             AudioChunk* aOutput)
 {
-  if (aInput.IsNull()) {
-    *aOutput = aInput;
-    return;
-  }
-
   float azimuth, elevation, gainL, gainR, normalizedAzimuth, distanceGain, coneGain;
   int inputChannels = aInput.mChannelData.Length();
 
diff --git a/content/media/webaudio/blink/HRTFPanner.cpp b/content/media/webaudio/blink/HRTFPanner.cpp
index d30e2fff812..8bc86b6ccfd 100644
--- a/content/media/webaudio/blink/HRTFPanner.cpp
+++ b/content/media/webaudio/blink/HRTFPanner.cpp
@@ -290,19 +290,16 @@ void HRTFPanner::pan(double desiredAzimuth, double elevation, const AudioChunk*
     }
 }
 
-double HRTFPanner::tailTime() const
+int HRTFPanner::maxTailFrames() const
 {
-    // Because HRTFPanner is implemented with a DelayKernel and a FFTConvolver, the tailTime of the HRTFPanner
-    // is the sum of the tailTime of the DelayKernel and the tailTime of the FFTConvolver, which is MaxDelayTimeSeconds
-    // and fftSize() / 2, respectively.
-    return MaxDelayTimeSeconds + (fftSize() / 2) / static_cast<double>(sampleRate());
-}
-
-double HRTFPanner::latencyTime() const
-{
-    // The latency of a FFTConvolver is also fftSize() / 2, and is in addition to its tailTime of the
-    // same value.
-    return (fftSize() / 2) / static_cast<double>(sampleRate());
+    // Although the ideal tail time would be the length of the impulse
+    // response, there is additional tail time from the approximations in the
+    // implementation.  Because HRTFPanner is implemented with a DelayKernel
+    // and a FFTConvolver, the tailTime of the HRTFPanner is the sum of the
+    // tailTime of the DelayKernel and the tailTime of the FFTConvolver.
+    // The FFTConvolver has a tail time of fftSize(), including latency of
+    // fftSize()/2.
+    return m_delayLineL.MaxDelayFrames() + fftSize();
 }
 
 } // namespace WebCore
diff --git a/content/media/webaudio/blink/HRTFPanner.h b/content/media/webaudio/blink/HRTFPanner.h
index b787dd88d2d..6c725a8a521 100644
--- a/content/media/webaudio/blink/HRTFPanner.h
+++ b/content/media/webaudio/blink/HRTFPanner.h
@@ -51,8 +51,7 @@ public:
 
     float sampleRate() const { return m_sampleRate; }
 
-    double tailTime() const;
-    double latencyTime() const;
+    int maxTailFrames() const;
 
 private:
     // Given an azimuth angle in the range -180 -> +180, returns the corresponding azimuth index for the database,