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