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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 THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_DYNAMICS_COMPRESSOR_KERNEL_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_DYNAMICS_COMPRESSOR_KERNEL_H_
#include <memory>
#include "third_party/blink/renderer/platform/audio/audio_array.h"
#include "third_party/blink/renderer/platform/platform_export.h"
#include "third_party/blink/renderer/platform/wtf/allocator.h"
#include "third_party/blink/renderer/platform/wtf/noncopyable.h"
#include "third_party/blink/renderer/platform/wtf/vector.h"
namespace blink {
class PLATFORM_EXPORT DynamicsCompressorKernel {
DISALLOW_NEW();
WTF_MAKE_NONCOPYABLE(DynamicsCompressorKernel);
public:
DynamicsCompressorKernel(float sample_rate, unsigned number_of_channels);
void SetNumberOfChannels(unsigned);
// Performs stereo-linked compression.
void Process(const float* source_channels[],
float* destination_channels[],
unsigned number_of_channels,
unsigned frames_to_process,
float db_threshold,
float db_knee,
float ratio,
float attack_time,
float release_time,
float pre_delay_time,
float db_post_gain,
float effect_blend,
float release_zone1,
float release_zone2,
float release_zone3,
float release_zone4);
void Reset();
unsigned LatencyFrames() const { return last_pre_delay_frames_; }
float SampleRate() const { return sample_rate_; }
float MeteringGain() const { return metering_gain_; }
double TailTime() const;
protected:
float sample_rate_;
float detector_average_;
float compressor_gain_;
// Metering
float metering_release_k_;
float metering_gain_;
// Lookahead section.
enum { kMaxPreDelayFrames = 1024 };
enum { kMaxPreDelayFramesMask = kMaxPreDelayFrames - 1 };
enum {
kDefaultPreDelayFrames = 256
}; // setPreDelayTime() will override this initial value
unsigned last_pre_delay_frames_;
void SetPreDelayTime(float);
Vector<std::unique_ptr<AudioFloatArray>> pre_delay_buffers_;
int pre_delay_read_index_;
int pre_delay_write_index_;
float max_attack_compression_diff_db_;
// Static compression curve.
float KneeCurve(float x, float k);
float Saturate(float x, float k);
float SlopeAt(float x, float k);
float KAtSlope(float desired_slope);
float UpdateStaticCurveParameters(float db_threshold,
float db_knee,
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 ratio_;
float slope_; // Inverse ratio.
// The input to output change below the threshold is linear 1:1.
float linear_threshold_;
float db_threshold_;
// 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 db_knee_;
float knee_threshold_;
float knee_threshold_db_;
float yknee_threshold_db_;
// Internal parameter for the knee portion of the curve.
float knee_;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_DYNAMICS_COMPRESSOR_KERNEL_H_
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