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+/*
+ * Copyright (C) 2011 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.
+ * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
+ *     its contributors may be used to endorse or promote products derived
+ *     from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE 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 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 DynamicsCompressorKernel_h
+#define DynamicsCompressorKernel_h
+
+#include "nsTArray.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/UniquePtr.h"
+
+namespace WebCore {
+
+class DynamicsCompressorKernel {
+ public:
+  DynamicsCompressorKernel(float sampleRate, unsigned numberOfChannels);
+
+  void setNumberOfChannels(unsigned);
+
+  // Performs stereo-linked compression.
+  void process(float* sourceChannels[], float* destinationChannels[],
+               unsigned numberOfChannels, unsigned framesToProcess,
+
+               float dbThreshold, float dbKnee, float ratio, float attackTime,
+               float releaseTime, float preDelayTime, float dbPostGain,
+               float effectBlend,
+
+               float releaseZone1, float releaseZone2, float releaseZone3,
+               float releaseZone4);
+
+  void reset();
+
+  unsigned latencyFrames() const { return m_lastPreDelayFrames; }
+
+  float sampleRate() const { return m_sampleRate; }
+
+  float meteringGain() const { return m_meteringGain; }
+
+  size_t sizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
+
+ protected:
+  float m_sampleRate;
+
+  float m_detectorAverage;
+  float m_compressorGain;
+
+  // Metering
+  float m_meteringReleaseK;
+  float m_meteringGain;
+
+  // Lookahead section.
+  enum { MaxPreDelayFrames = 1024 };
+  enum { MaxPreDelayFramesMask = MaxPreDelayFrames - 1 };
+  enum {
+    DefaultPreDelayFrames = 256
+  };  // setPreDelayTime() will override this initial value
+  unsigned m_lastPreDelayFrames;
+  void setPreDelayTime(float);
+
+  nsTArray<mozilla::UniquePtr<float[]>> m_preDelayBuffers;
+  int m_preDelayReadIndex;
+  int m_preDelayWriteIndex;
+
+  float m_maxAttackCompressionDiffDb;
+
+  // Static compression curve.
+  float kneeCurve(float x, float k);
+  float saturate(float x, float k);
+  float slopeAt(float x, float k);
+  float kAtSlope(float desiredSlope);
+
+  float updateStaticCurveParameters(float dbThreshold, float dbKnee,
+                                    float ratio);
+
+  // Amount of input change in dB required for 1 dB of output change.
+  // This applies to the portion of the curve above m_kneeThresholdDb (see
+  // below).
+  float m_ratio;
+  float m_slope;  // Inverse ratio.
+
+  // The input to output change below the threshold is linear 1:1.
+  float m_linearThreshold;
+  float m_dbThreshold;
+
+  // m_dbKnee is the number of dB above the threshold before we enter the
+  // "ratio" portion of the curve. m_kneeThresholdDb = m_dbThreshold + m_dbKnee
+  // The portion between m_dbThreshold and m_kneeThresholdDb is the "soft knee"
+  // portion of the curve which transitions smoothly from the linear portion to
+  // the ratio portion.
+  float m_dbKnee;
+  float m_kneeThreshold;
+  float m_kneeThresholdDb;
+  float m_ykneeThresholdDb;
+
+  // Internal parameter for the knee portion of the curve.
+  float m_K;
+};
+
+}  // namespace WebCore
+
+#endif  // DynamicsCompressorKernel_h