michael@0: /*
michael@0:  * Copyright (C) 2011 Google Inc. All rights reserved.
michael@0:  *
michael@0:  * Redistribution and use in source and binary forms, with or without
michael@0:  * modification, are permitted provided that the following conditions
michael@0:  * are met:
michael@0:  *
michael@0:  * 1.  Redistributions of source code must retain the above copyright
michael@0:  *     notice, this list of conditions and the following disclaimer.
michael@0:  * 2.  Redistributions in binary form must reproduce the above copyright
michael@0:  *     notice, this list of conditions and the following disclaimer in the
michael@0:  *     documentation and/or other materials provided with the distribution.
michael@0:  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
michael@0:  *     its contributors may be used to endorse or promote products derived
michael@0:  *     from this software without specific prior written permission.
michael@0:  *
michael@0:  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
michael@0:  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
michael@0:  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
michael@0:  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
michael@0:  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
michael@0:  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
michael@0:  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
michael@0:  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
michael@0:  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
michael@0:  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
michael@0:  */
michael@0: 
michael@0: #include "DynamicsCompressorKernel.h"
michael@0: 
michael@0: #include "DenormalDisabler.h"
michael@0: #include <algorithm>
michael@0: 
michael@0: #include "mozilla/FloatingPoint.h"
michael@0: #include "mozilla/Constants.h"
michael@0: #include "WebAudioUtils.h"
michael@0: 
michael@0: using namespace std;
michael@0: 
michael@0: using namespace mozilla::dom; // for WebAudioUtils
michael@0: using mozilla::IsInfinite;
michael@0: using mozilla::IsNaN;
michael@0: 
michael@0: namespace WebCore {
michael@0: 
michael@0: 
michael@0: // Metering hits peaks instantly, but releases this fast (in seconds).
michael@0: const float meteringReleaseTimeConstant = 0.325f;
michael@0: 
michael@0: const float uninitializedValue = -1;
michael@0: 
michael@0: DynamicsCompressorKernel::DynamicsCompressorKernel(float sampleRate, unsigned numberOfChannels)
michael@0:     : m_sampleRate(sampleRate)
michael@0:     , m_lastPreDelayFrames(DefaultPreDelayFrames)
michael@0:     , m_preDelayReadIndex(0)
michael@0:     , m_preDelayWriteIndex(DefaultPreDelayFrames)
michael@0:     , m_ratio(uninitializedValue)
michael@0:     , m_slope(uninitializedValue)
michael@0:     , m_linearThreshold(uninitializedValue)
michael@0:     , m_dbThreshold(uninitializedValue)
michael@0:     , m_dbKnee(uninitializedValue)
michael@0:     , m_kneeThreshold(uninitializedValue)
michael@0:     , m_kneeThresholdDb(uninitializedValue)
michael@0:     , m_ykneeThresholdDb(uninitializedValue)
michael@0:     , m_K(uninitializedValue)
michael@0: {
michael@0:     setNumberOfChannels(numberOfChannels);
michael@0: 
michael@0:     // Initializes most member variables
michael@0:     reset();
michael@0: 
michael@0:     m_meteringReleaseK =
michael@0:         static_cast<float>(WebAudioUtils::DiscreteTimeConstantForSampleRate(meteringReleaseTimeConstant, sampleRate));
michael@0: }
michael@0: 
michael@0: size_t DynamicsCompressorKernel::sizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
michael@0: {
michael@0:     size_t amount = 0;
michael@0:     amount += m_preDelayBuffers.SizeOfExcludingThis(aMallocSizeOf);
michael@0:     for (size_t i = 0; i < m_preDelayBuffers.Length(); i++) {
michael@0:         amount += m_preDelayBuffers[i].SizeOfExcludingThis(aMallocSizeOf);
michael@0:     }
michael@0: 
michael@0:     return amount;
michael@0: }
michael@0: 
michael@0: void DynamicsCompressorKernel::setNumberOfChannels(unsigned numberOfChannels)
michael@0: {
michael@0:     if (m_preDelayBuffers.Length() == numberOfChannels)
michael@0:         return;
michael@0: 
michael@0:     m_preDelayBuffers.Clear();
michael@0:     for (unsigned i = 0; i < numberOfChannels; ++i)
michael@0:         m_preDelayBuffers.AppendElement(new float[MaxPreDelayFrames]);
michael@0: }
michael@0: 
michael@0: void DynamicsCompressorKernel::setPreDelayTime(float preDelayTime)
michael@0: {
michael@0:     // Re-configure look-ahead section pre-delay if delay time has changed.
michael@0:     unsigned preDelayFrames = preDelayTime * sampleRate();
michael@0:     if (preDelayFrames > MaxPreDelayFrames - 1)
michael@0:         preDelayFrames = MaxPreDelayFrames - 1;
michael@0: 
michael@0:     if (m_lastPreDelayFrames != preDelayFrames) {
michael@0:         m_lastPreDelayFrames = preDelayFrames;
michael@0:         for (unsigned i = 0; i < m_preDelayBuffers.Length(); ++i)
michael@0:             memset(m_preDelayBuffers[i], 0, sizeof(float) * MaxPreDelayFrames);
michael@0: 
michael@0:         m_preDelayReadIndex = 0;
michael@0:         m_preDelayWriteIndex = preDelayFrames;
michael@0:     }
michael@0: }
michael@0: 
michael@0: // Exponential curve for the knee.
michael@0: // It is 1st derivative matched at m_linearThreshold and asymptotically approaches the value m_linearThreshold + 1 / k.
michael@0: float DynamicsCompressorKernel::kneeCurve(float x, float k)
michael@0: {
michael@0:     // Linear up to threshold.
michael@0:     if (x < m_linearThreshold)
michael@0:         return x;
michael@0: 
michael@0:     return m_linearThreshold + (1 - expf(-k * (x - m_linearThreshold))) / k;
michael@0: }
michael@0: 
michael@0: // Full compression curve with constant ratio after knee.
michael@0: float DynamicsCompressorKernel::saturate(float x, float k)
michael@0: {
michael@0:     float y;
michael@0: 
michael@0:     if (x < m_kneeThreshold)
michael@0:         y = kneeCurve(x, k);
michael@0:     else {
michael@0:         // Constant ratio after knee.
michael@0:         float xDb = WebAudioUtils::ConvertLinearToDecibels(x, -1000.0f);
michael@0:         float yDb = m_ykneeThresholdDb + m_slope * (xDb - m_kneeThresholdDb);
michael@0: 
michael@0:         y = WebAudioUtils::ConvertDecibelsToLinear(yDb);
michael@0:     }
michael@0: 
michael@0:     return y;
michael@0: }
michael@0: 
michael@0: // Approximate 1st derivative with input and output expressed in dB.
michael@0: // This slope is equal to the inverse of the compression "ratio".
michael@0: // In other words, a compression ratio of 20 would be a slope of 1/20.
michael@0: float DynamicsCompressorKernel::slopeAt(float x, float k)
michael@0: {
michael@0:     if (x < m_linearThreshold)
michael@0:         return 1;
michael@0: 
michael@0:     float x2 = x * 1.001;
michael@0: 
michael@0:     float xDb = WebAudioUtils::ConvertLinearToDecibels(x, -1000.0f);
michael@0:     float x2Db = WebAudioUtils::ConvertLinearToDecibels(x2, -1000.0f);
michael@0: 
michael@0:     float yDb = WebAudioUtils::ConvertLinearToDecibels(kneeCurve(x, k), -1000.0f);
michael@0:     float y2Db = WebAudioUtils::ConvertLinearToDecibels(kneeCurve(x2, k), -1000.0f);
michael@0: 
michael@0:     float m = (y2Db - yDb) / (x2Db - xDb);
michael@0: 
michael@0:     return m;
michael@0: }
michael@0: 
michael@0: float DynamicsCompressorKernel::kAtSlope(float desiredSlope)
michael@0: {
michael@0:     float xDb = m_dbThreshold + m_dbKnee;
michael@0:     float x = WebAudioUtils::ConvertDecibelsToLinear(xDb);
michael@0: 
michael@0:     // Approximate k given initial values.
michael@0:     float minK = 0.1;
michael@0:     float maxK = 10000;
michael@0:     float k = 5;
michael@0: 
michael@0:     for (int i = 0; i < 15; ++i) {
michael@0:         // A high value for k will more quickly asymptotically approach a slope of 0.
michael@0:         float slope = slopeAt(x, k);
michael@0: 
michael@0:         if (slope < desiredSlope) {
michael@0:             // k is too high.
michael@0:             maxK = k;
michael@0:         } else {
michael@0:             // k is too low.
michael@0:             minK = k;
michael@0:         }
michael@0: 
michael@0:         // Re-calculate based on geometric mean.
michael@0:         k = sqrtf(minK * maxK);
michael@0:     }
michael@0: 
michael@0:     return k;
michael@0: }
michael@0: 
michael@0: float DynamicsCompressorKernel::updateStaticCurveParameters(float dbThreshold, float dbKnee, float ratio)
michael@0: {
michael@0:     if (dbThreshold != m_dbThreshold || dbKnee != m_dbKnee || ratio != m_ratio) {
michael@0:         // Threshold and knee.
michael@0:         m_dbThreshold = dbThreshold;
michael@0:         m_linearThreshold = WebAudioUtils::ConvertDecibelsToLinear(dbThreshold);
michael@0:         m_dbKnee = dbKnee;
michael@0: 
michael@0:         // Compute knee parameters.
michael@0:         m_ratio = ratio;
michael@0:         m_slope = 1 / m_ratio;
michael@0: 
michael@0:         float k = kAtSlope(1 / m_ratio);
michael@0: 
michael@0:         m_kneeThresholdDb = dbThreshold + dbKnee;
michael@0:         m_kneeThreshold = WebAudioUtils::ConvertDecibelsToLinear(m_kneeThresholdDb);
michael@0: 
michael@0:         m_ykneeThresholdDb = WebAudioUtils::ConvertLinearToDecibels(kneeCurve(m_kneeThreshold, k), -1000.0f);
michael@0: 
michael@0:         m_K = k;
michael@0:     }
michael@0:     return m_K;
michael@0: }
michael@0: 
michael@0: void DynamicsCompressorKernel::process(float* sourceChannels[],
michael@0:                                        float* destinationChannels[],
michael@0:                                        unsigned numberOfChannels,
michael@0:                                        unsigned framesToProcess,
michael@0: 
michael@0:                                        float dbThreshold,
michael@0:                                        float dbKnee,
michael@0:                                        float ratio,
michael@0:                                        float attackTime,
michael@0:                                        float releaseTime,
michael@0:                                        float preDelayTime,
michael@0:                                        float dbPostGain,
michael@0:                                        float effectBlend, /* equal power crossfade */
michael@0: 
michael@0:                                        float releaseZone1,
michael@0:                                        float releaseZone2,
michael@0:                                        float releaseZone3,
michael@0:                                        float releaseZone4
michael@0:                                        )
michael@0: {
michael@0:     MOZ_ASSERT(m_preDelayBuffers.Length() == numberOfChannels);
michael@0: 
michael@0:     float sampleRate = this->sampleRate();
michael@0: 
michael@0:     float dryMix = 1 - effectBlend;
michael@0:     float wetMix = effectBlend;
michael@0: 
michael@0:     float k = updateStaticCurveParameters(dbThreshold, dbKnee, ratio);
michael@0: 
michael@0:     // Makeup gain.
michael@0:     float fullRangeGain = saturate(1, k);
michael@0:     float fullRangeMakeupGain = 1 / fullRangeGain;
michael@0: 
michael@0:     // Empirical/perceptual tuning.
michael@0:     fullRangeMakeupGain = powf(fullRangeMakeupGain, 0.6f);
michael@0: 
michael@0:     float masterLinearGain = WebAudioUtils::ConvertDecibelsToLinear(dbPostGain) * fullRangeMakeupGain;
michael@0: 
michael@0:     // Attack parameters.
michael@0:     attackTime = max(0.001f, attackTime);
michael@0:     float attackFrames = attackTime * sampleRate;
michael@0: 
michael@0:     // Release parameters.
michael@0:     float releaseFrames = sampleRate * releaseTime;
michael@0: 
michael@0:     // Detector release time.
michael@0:     float satReleaseTime = 0.0025f;
michael@0:     float satReleaseFrames = satReleaseTime * sampleRate;
michael@0: 
michael@0:     // Create a smooth function which passes through four points.
michael@0: 
michael@0:     // Polynomial of the form
michael@0:     // y = a + b*x + c*x^2 + d*x^3 + e*x^4;
michael@0: 
michael@0:     float y1 = releaseFrames * releaseZone1;
michael@0:     float y2 = releaseFrames * releaseZone2;
michael@0:     float y3 = releaseFrames * releaseZone3;
michael@0:     float y4 = releaseFrames * releaseZone4;
michael@0: 
michael@0:     // All of these coefficients were derived for 4th order polynomial curve fitting where the y values
michael@0:     // match the evenly spaced x values as follows: (y1 : x == 0, y2 : x == 1, y3 : x == 2, y4 : x == 3)
michael@0:     float kA = 0.9999999999999998f*y1 + 1.8432219684323923e-16f*y2 - 1.9373394351676423e-16f*y3 + 8.824516011816245e-18f*y4;
michael@0:     float kB = -1.5788320352845888f*y1 + 2.3305837032074286f*y2 - 0.9141194204840429f*y3 + 0.1623677525612032f*y4;
michael@0:     float kC = 0.5334142869106424f*y1 - 1.272736789213631f*y2 + 0.9258856042207512f*y3 - 0.18656310191776226f*y4;
michael@0:     float kD = 0.08783463138207234f*y1 - 0.1694162967925622f*y2 + 0.08588057951595272f*y3 - 0.00429891410546283f*y4;
michael@0:     float kE = -0.042416883008123074f*y1 + 0.1115693827987602f*y2 - 0.09764676325265872f*y3 + 0.028494263462021576f*y4;
michael@0: 
michael@0:     // x ranges from 0 -> 3       0    1    2   3
michael@0:     //                           -15  -10  -5   0db
michael@0: 
michael@0:     // y calculates adaptive release frames depending on the amount of compression.
michael@0: 
michael@0:     setPreDelayTime(preDelayTime);
michael@0: 
michael@0:     const int nDivisionFrames = 32;
michael@0: 
michael@0:     const int nDivisions = framesToProcess / nDivisionFrames;
michael@0: 
michael@0:     unsigned frameIndex = 0;
michael@0:     for (int i = 0; i < nDivisions; ++i) {
michael@0:         // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
michael@0:         // Calculate desired gain
michael@0:         // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
michael@0: 
michael@0:         // Fix gremlins.
michael@0:         if (IsNaN(m_detectorAverage))
michael@0:             m_detectorAverage = 1;
michael@0:         if (IsInfinite(m_detectorAverage))
michael@0:             m_detectorAverage = 1;
michael@0: 
michael@0:         float desiredGain = m_detectorAverage;
michael@0: 
michael@0:         // Pre-warp so we get desiredGain after sin() warp below.
michael@0:         float scaledDesiredGain = asinf(desiredGain) / (0.5f * M_PI);
michael@0: 
michael@0:         // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
michael@0:         // Deal with envelopes
michael@0:         // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
michael@0: 
michael@0:         // envelopeRate is the rate we slew from current compressor level to the desired level.
michael@0:         // The exact rate depends on if we're attacking or releasing and by how much.
michael@0:         float envelopeRate;
michael@0: 
michael@0:         bool isReleasing = scaledDesiredGain > m_compressorGain;
michael@0: 
michael@0:         // compressionDiffDb is the difference between current compression level and the desired level.
michael@0:         float compressionDiffDb = WebAudioUtils::ConvertLinearToDecibels(m_compressorGain / scaledDesiredGain, -1000.0f);
michael@0: 
michael@0:         if (isReleasing) {
michael@0:             // Release mode - compressionDiffDb should be negative dB
michael@0:             m_maxAttackCompressionDiffDb = -1;
michael@0: 
michael@0:             // Fix gremlins.
michael@0:             if (IsNaN(compressionDiffDb))
michael@0:                 compressionDiffDb = -1;
michael@0:             if (IsInfinite(compressionDiffDb))
michael@0:                 compressionDiffDb = -1;
michael@0: 
michael@0:             // Adaptive release - higher compression (lower compressionDiffDb)  releases faster.
michael@0: 
michael@0:             // Contain within range: -12 -> 0 then scale to go from 0 -> 3
michael@0:             float x = compressionDiffDb;
michael@0:             x = max(-12.0f, x);
michael@0:             x = min(0.0f, x);
michael@0:             x = 0.25f * (x + 12);
michael@0: 
michael@0:             // Compute adaptive release curve using 4th order polynomial.
michael@0:             // Normal values for the polynomial coefficients would create a monotonically increasing function.
michael@0:             float x2 = x * x;
michael@0:             float x3 = x2 * x;
michael@0:             float x4 = x2 * x2;
michael@0:             float releaseFrames = kA + kB * x + kC * x2 + kD * x3 + kE * x4;
michael@0: 
michael@0: #define kSpacingDb 5
michael@0:             float dbPerFrame = kSpacingDb / releaseFrames;
michael@0: 
michael@0:             envelopeRate = WebAudioUtils::ConvertDecibelsToLinear(dbPerFrame);
michael@0:         } else {
michael@0:             // Attack mode - compressionDiffDb should be positive dB
michael@0: 
michael@0:             // Fix gremlins.
michael@0:             if (IsNaN(compressionDiffDb))
michael@0:                 compressionDiffDb = 1;
michael@0:             if (IsInfinite(compressionDiffDb))
michael@0:                 compressionDiffDb = 1;
michael@0: 
michael@0:             // As long as we're still in attack mode, use a rate based off
michael@0:             // the largest compressionDiffDb we've encountered so far.
michael@0:             if (m_maxAttackCompressionDiffDb == -1 || m_maxAttackCompressionDiffDb < compressionDiffDb)
michael@0:                 m_maxAttackCompressionDiffDb = compressionDiffDb;
michael@0: 
michael@0:             float effAttenDiffDb = max(0.5f, m_maxAttackCompressionDiffDb);
michael@0: 
michael@0:             float x = 0.25f / effAttenDiffDb;
michael@0:             envelopeRate = 1 - powf(x, 1 / attackFrames);
michael@0:         }
michael@0: 
michael@0:         // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
michael@0:         // Inner loop - calculate shaped power average - apply compression.
michael@0:         // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
michael@0: 
michael@0:         {
michael@0:             int preDelayReadIndex = m_preDelayReadIndex;
michael@0:             int preDelayWriteIndex = m_preDelayWriteIndex;
michael@0:             float detectorAverage = m_detectorAverage;
michael@0:             float compressorGain = m_compressorGain;
michael@0: 
michael@0:             int loopFrames = nDivisionFrames;
michael@0:             while (loopFrames--) {
michael@0:                 float compressorInput = 0;
michael@0: 
michael@0:                 // Predelay signal, computing compression amount from un-delayed version.
michael@0:                 for (unsigned i = 0; i < numberOfChannels; ++i) {
michael@0:                     float* delayBuffer = m_preDelayBuffers[i];
michael@0:                     float undelayedSource = sourceChannels[i][frameIndex];
michael@0:                     delayBuffer[preDelayWriteIndex] = undelayedSource;
michael@0: 
michael@0:                     float absUndelayedSource = undelayedSource > 0 ? undelayedSource : -undelayedSource;
michael@0:                     if (compressorInput < absUndelayedSource)
michael@0:                         compressorInput = absUndelayedSource;
michael@0:                 }
michael@0: 
michael@0:                 // Calculate shaped power on undelayed input.
michael@0: 
michael@0:                 float scaledInput = compressorInput;
michael@0:                 float absInput = scaledInput > 0 ? scaledInput : -scaledInput;
michael@0: 
michael@0:                 // Put through shaping curve.
michael@0:                 // This is linear up to the threshold, then enters a "knee" portion followed by the "ratio" portion.
michael@0:                 // The transition from the threshold to the knee is smooth (1st derivative matched).
michael@0:                 // The transition from the knee to the ratio portion is smooth (1st derivative matched).
michael@0:                 float shapedInput = saturate(absInput, k);
michael@0: 
michael@0:                 float attenuation = absInput <= 0.0001f ? 1 : shapedInput / absInput;
michael@0: 
michael@0:                 float attenuationDb = -WebAudioUtils::ConvertLinearToDecibels(attenuation, -1000.0f);
michael@0:                 attenuationDb = max(2.0f, attenuationDb);
michael@0: 
michael@0:                 float dbPerFrame = attenuationDb / satReleaseFrames;
michael@0: 
michael@0:                 float satReleaseRate = WebAudioUtils::ConvertDecibelsToLinear(dbPerFrame) - 1;
michael@0: 
michael@0:                 bool isRelease = (attenuation > detectorAverage);
michael@0:                 float rate = isRelease ? satReleaseRate : 1;
michael@0: 
michael@0:                 detectorAverage += (attenuation - detectorAverage) * rate;
michael@0:                 detectorAverage = min(1.0f, detectorAverage);
michael@0: 
michael@0:                 // Fix gremlins.
michael@0:                 if (IsNaN(detectorAverage))
michael@0:                     detectorAverage = 1;
michael@0:                 if (IsInfinite(detectorAverage))
michael@0:                     detectorAverage = 1;
michael@0: 
michael@0:                 // Exponential approach to desired gain.
michael@0:                 if (envelopeRate < 1) {
michael@0:                     // Attack - reduce gain to desired.
michael@0:                     compressorGain += (scaledDesiredGain - compressorGain) * envelopeRate;
michael@0:                 } else {
michael@0:                     // Release - exponentially increase gain to 1.0
michael@0:                     compressorGain *= envelopeRate;
michael@0:                     compressorGain = min(1.0f, compressorGain);
michael@0:                 }
michael@0: 
michael@0:                 // Warp pre-compression gain to smooth out sharp exponential transition points.
michael@0:                 float postWarpCompressorGain = sinf(0.5f * M_PI * compressorGain);
michael@0: 
michael@0:                 // Calculate total gain using master gain and effect blend.
michael@0:                 float totalGain = dryMix + wetMix * masterLinearGain * postWarpCompressorGain;
michael@0: 
michael@0:                 // Calculate metering.
michael@0:                 float dbRealGain = 20 * log10(postWarpCompressorGain);
michael@0:                 if (dbRealGain < m_meteringGain)
michael@0:                     m_meteringGain = dbRealGain;
michael@0:                 else
michael@0:                     m_meteringGain += (dbRealGain - m_meteringGain) * m_meteringReleaseK;
michael@0: 
michael@0:                 // Apply final gain.
michael@0:                 for (unsigned i = 0; i < numberOfChannels; ++i) {
michael@0:                     float* delayBuffer = m_preDelayBuffers[i];
michael@0:                     destinationChannels[i][frameIndex] = delayBuffer[preDelayReadIndex] * totalGain;
michael@0:                 }
michael@0: 
michael@0:                 frameIndex++;
michael@0:                 preDelayReadIndex = (preDelayReadIndex + 1) & MaxPreDelayFramesMask;
michael@0:                 preDelayWriteIndex = (preDelayWriteIndex + 1) & MaxPreDelayFramesMask;
michael@0:             }
michael@0: 
michael@0:             // Locals back to member variables.
michael@0:             m_preDelayReadIndex = preDelayReadIndex;
michael@0:             m_preDelayWriteIndex = preDelayWriteIndex;
michael@0:             m_detectorAverage = DenormalDisabler::flushDenormalFloatToZero(detectorAverage);
michael@0:             m_compressorGain = DenormalDisabler::flushDenormalFloatToZero(compressorGain);
michael@0:         }
michael@0:     }
michael@0: }
michael@0: 
michael@0: void DynamicsCompressorKernel::reset()
michael@0: {
michael@0:     m_detectorAverage = 0;
michael@0:     m_compressorGain = 1;
michael@0:     m_meteringGain = 1;
michael@0: 
michael@0:     // Predelay section.
michael@0:     for (unsigned i = 0; i < m_preDelayBuffers.Length(); ++i)
michael@0:         memset(m_preDelayBuffers[i], 0, sizeof(float) * MaxPreDelayFrames);
michael@0: 
michael@0:     m_preDelayReadIndex = 0;
michael@0:     m_preDelayWriteIndex = DefaultPreDelayFrames;
michael@0: 
michael@0:     m_maxAttackCompressionDiffDb = -1; // uninitialized state
michael@0: }
michael@0: 
michael@0: } // namespace WebCore