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diff --git a/dom/media/webaudio/blink/HRTFPanner.h b/dom/media/webaudio/blink/HRTFPanner.h
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+++ b/dom/media/webaudio/blink/HRTFPanner.h
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+/*
+ * Copyright (C) 2010, Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1.  Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2.  Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef HRTFPanner_h
+#define HRTFPanner_h
+
+#include "FFTConvolver.h"
+#include "DelayBuffer.h"
+#include "mozilla/MemoryReporting.h"
+
+namespace mozilla {
+class AudioBlock;
+} // namespace mozilla
+
+namespace WebCore {
+
+typedef nsTArray<float> AudioFloatArray;
+
+class HRTFDatabaseLoader;
+
+using mozilla::AudioBlock;
+
+class HRTFPanner {
+public:
+    HRTFPanner(float sampleRate, already_AddRefed<HRTFDatabaseLoader> databaseLoader);
+    ~HRTFPanner();
+
+    // chunk durations must be 128
+    void pan(double azimuth, double elevation, const AudioBlock* inputBus, AudioBlock* outputBus);
+    void reset();
+
+    size_t fftSize() const { return m_convolverL1.fftSize(); }
+
+    float sampleRate() const { return m_sampleRate; }
+
+    int maxTailFrames() const;
+
+    size_t sizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
+
+private:
+    // Given an azimuth angle in the range -180 -> +180, returns the corresponding azimuth index for the database,
+    // and azimuthBlend which is an interpolation value from 0 -> 1.
+    int calculateDesiredAzimuthIndexAndBlend(double azimuth, double& azimuthBlend);
+
+    RefPtr<HRTFDatabaseLoader> m_databaseLoader;
+
+    float m_sampleRate;
+
+    // We maintain two sets of convolvers for smooth cross-faded interpolations when
+    // then azimuth and elevation are dynamically changing.
+    // When the azimuth and elevation are not changing, we simply process with one of the two sets.
+    // Initially we use CrossfadeSelection1 corresponding to m_convolverL1 and m_convolverR1.
+    // Whenever the azimuth or elevation changes, a crossfade is initiated to transition
+    // to the new position. So if we're currently processing with CrossfadeSelection1, then
+    // we transition to CrossfadeSelection2 (and vice versa).
+    // If we're in the middle of a transition, then we wait until it is complete before
+    // initiating a new transition.
+
+    // Selects either the convolver set (m_convolverL1, m_convolverR1) or (m_convolverL2, m_convolverR2).
+    enum CrossfadeSelection {
+        CrossfadeSelection1,
+        CrossfadeSelection2
+    };
+
+    CrossfadeSelection m_crossfadeSelection;
+
+    // azimuth/elevation for CrossfadeSelection1.
+    int m_azimuthIndex1;
+    double m_elevation1;
+
+    // azimuth/elevation for CrossfadeSelection2.
+    int m_azimuthIndex2;
+    double m_elevation2;
+
+    // A crossfade value 0 <= m_crossfadeX <= 1.
+    float m_crossfadeX;
+
+    // Per-sample-frame crossfade value increment.
+    float m_crossfadeIncr;
+
+    FFTConvolver m_convolverL1;
+    FFTConvolver m_convolverR1;
+    FFTConvolver m_convolverL2;
+    FFTConvolver m_convolverR2;
+
+    mozilla::DelayBuffer m_delayLine;
+
+    AudioFloatArray m_tempL1;
+    AudioFloatArray m_tempR1;
+    AudioFloatArray m_tempL2;
+    AudioFloatArray m_tempR2;
+};
+
+} // namespace WebCore
+
+#endif // HRTFPanner_h