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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_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_DYNAMICS_COMPRESSOR_H_
#include <array>
#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/allocator.h"
#include "third_party/blink/renderer/platform/wtf/vector.h"
namespace blink {
class AudioBus;
// DynamicsCompressor implements a flexible audio dynamics compression effect
// such as is commonly used in musical production and game audio. It lowers the
// volume of the loudest parts of the signal and raises the volume of the
// softest parts, making the sound richer, fuller, and more controlled.
class PLATFORM_EXPORT DynamicsCompressor final {
USING_FAST_MALLOC(DynamicsCompressor);
public:
enum {
kParamThreshold,
kParamKnee,
kParamRatio,
kParamAttack,
kParamRelease,
kParamReduction,
kParamLast
};
DynamicsCompressor(float sample_rate, unsigned number_of_channels);
DynamicsCompressor(const DynamicsCompressor&) = delete;
DynamicsCompressor& operator=(const DynamicsCompressor&) = delete;
// Performs stereo-linked compression.
void Process(const AudioBus* source_bus,
AudioBus* destination_bus,
unsigned frames_to_process);
void Reset();
void SetNumberOfChannels(unsigned);
void SetParameterValue(unsigned parameter_id, float value);
float ParameterValue(unsigned parameter_id) const;
float SampleRate() const;
float Nyquist() const;
double TailTime() const;
double LatencyTime() const;
bool RequiresTailProcessing() const;
protected:
void InitializeParameters();
void SetPreDelayTime(float);
// Static compression curve.
float KneeCurve(float x, float k) const;
float Saturate(float x, float k) const;
float KAtSlope(float desired_slope) const;
float UpdateStaticCurveParameters(float db_threshold,
float db_knee,
float ratio);
unsigned number_of_channels_;
// parameters_ holds the tweakable compressor parameters.
std::array<float, kParamLast> parameters_;
float sample_rate_;
std::unique_ptr<const float*[]> source_channels_;
std::unique_ptr<float*[]> destination_channels_;
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_ = kDefaultPreDelayFrames;
Vector<std::unique_ptr<AudioFloatArray>> pre_delay_buffers_;
int pre_delay_read_index_ = 0;
int pre_delay_write_index_ = kDefaultPreDelayFrames;
float db_max_attack_compression_diff_;
// Amount of input change in dB required for 1 dB of output change.
// This applies to the portion of the curve above db_knee_threshold_ (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_;
// db_knee_ is the number of dB above the threshold before we enter the
// "ratio" portion of the curve.
// db_knee_threshold_ = db_threshold_ + db_knee_
// The portion between db_threshold_ and db_knee_threshold_ 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 db_knee_threshold_;
float db_yknee_threshold_;
// Internal parameter for the knee portion of the curve.
float knee_;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_DYNAMICS_COMPRESSOR_H_
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