bcec8b0b21
This is from the upstream library commit id 3326535126e435f1ba647885ce43a8f0f3d317eb, corresponding to Chromium 88.0.4290.1.
77 lines
3.0 KiB
C++
77 lines
3.0 KiB
C++
/*
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* Copyright (c) 2018 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef MODULES_AUDIO_PROCESSING_AGC2_LIMITER_DB_GAIN_CURVE_H_
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#define MODULES_AUDIO_PROCESSING_AGC2_LIMITER_DB_GAIN_CURVE_H_
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#include <array>
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#include "modules/audio_processing/agc2/agc2_testing_common.h"
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namespace webrtc {
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// A class for computing a limiter gain curve (in dB scale) given a set of
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// hard-coded parameters (namely, kLimiterDbGainCurveMaxInputLevelDbFs,
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// kLimiterDbGainCurveKneeSmoothnessDb, and
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// kLimiterDbGainCurveCompressionRatio). The generated curve consists of four
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// regions: identity (linear), knee (quadratic polynomial), compression
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// (linear), saturation (linear). The aforementioned constants are used to shape
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// the different regions.
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class LimiterDbGainCurve {
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public:
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LimiterDbGainCurve();
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double max_input_level_db() const { return max_input_level_db_; }
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double max_input_level_linear() const { return max_input_level_linear_; }
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double knee_start_linear() const { return knee_start_linear_; }
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double limiter_start_linear() const { return limiter_start_linear_; }
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// These methods can be marked 'constexpr' in C++ 14.
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double GetOutputLevelDbfs(double input_level_dbfs) const;
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double GetGainLinear(double input_level_linear) const;
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double GetGainFirstDerivativeLinear(double x) const;
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double GetGainIntegralLinear(double x0, double x1) const;
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private:
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double GetKneeRegionOutputLevelDbfs(double input_level_dbfs) const;
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double GetCompressorRegionOutputLevelDbfs(double input_level_dbfs) const;
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static constexpr double max_input_level_db_ = test::kLimiterMaxInputLevelDbFs;
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static constexpr double knee_smoothness_db_ = test::kLimiterKneeSmoothnessDb;
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static constexpr double compression_ratio_ = test::kLimiterCompressionRatio;
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const double max_input_level_linear_;
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// Do not modify signal with level <= knee_start_dbfs_.
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const double knee_start_dbfs_;
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const double knee_start_linear_;
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// The upper end of the knee region, which is between knee_start_dbfs_ and
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// limiter_start_dbfs_.
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const double limiter_start_dbfs_;
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const double limiter_start_linear_;
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// Coefficients {a, b, c} of the knee region polynomial
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// ax^2 + bx + c in the DB scale.
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const std::array<double, 3> knee_region_polynomial_;
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// Parameters for the computation of the first derivative of GetGainLinear().
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const double gain_curve_limiter_d1_;
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const double gain_curve_limiter_d2_;
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// Parameters for the computation of the integral of GetGainLinear().
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const double gain_curve_limiter_i1_;
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const double gain_curve_limiter_i2_;
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};
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} // namespace webrtc
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#endif // MODULES_AUDIO_PROCESSING_AGC2_LIMITER_DB_GAIN_CURVE_H_
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