Update to current webrtc library
This is from the upstream library commit id 3326535126e435f1ba647885ce43a8f0f3d317eb, corresponding to Chromium 88.0.4290.1.
This commit is contained in:
138
webrtc/modules/audio_processing/agc2/limiter_db_gain_curve.cc
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138
webrtc/modules/audio_processing/agc2/limiter_db_gain_curve.cc
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/*
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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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#include "modules/audio_processing/agc2/limiter_db_gain_curve.h"
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#include <cmath>
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#include "common_audio/include/audio_util.h"
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#include "modules/audio_processing/agc2/agc2_common.h"
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#include "rtc_base/checks.h"
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namespace webrtc {
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namespace {
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double ComputeKneeStart(double max_input_level_db,
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double knee_smoothness_db,
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double compression_ratio) {
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RTC_CHECK_LT((compression_ratio - 1.0) * knee_smoothness_db /
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(2.0 * compression_ratio),
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max_input_level_db);
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return -knee_smoothness_db / 2.0 -
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max_input_level_db / (compression_ratio - 1.0);
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}
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std::array<double, 3> ComputeKneeRegionPolynomial(double knee_start_dbfs,
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double knee_smoothness_db,
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double compression_ratio) {
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const double a = (1.0 - compression_ratio) /
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(2.0 * knee_smoothness_db * compression_ratio);
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const double b = 1.0 - 2.0 * a * knee_start_dbfs;
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const double c = a * knee_start_dbfs * knee_start_dbfs;
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return {{a, b, c}};
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}
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double ComputeLimiterD1(double max_input_level_db, double compression_ratio) {
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return (std::pow(10.0, -max_input_level_db / (20.0 * compression_ratio)) *
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(1.0 - compression_ratio) / compression_ratio) /
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kMaxAbsFloatS16Value;
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}
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constexpr double ComputeLimiterD2(double compression_ratio) {
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return (1.0 - 2.0 * compression_ratio) / compression_ratio;
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}
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double ComputeLimiterI2(double max_input_level_db,
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double compression_ratio,
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double gain_curve_limiter_i1) {
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RTC_CHECK_NE(gain_curve_limiter_i1, 0.f);
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return std::pow(10.0, -max_input_level_db / (20.0 * compression_ratio)) /
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gain_curve_limiter_i1 /
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std::pow(kMaxAbsFloatS16Value, gain_curve_limiter_i1 - 1);
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}
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} // namespace
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LimiterDbGainCurve::LimiterDbGainCurve()
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: max_input_level_linear_(DbfsToFloatS16(max_input_level_db_)),
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knee_start_dbfs_(ComputeKneeStart(max_input_level_db_,
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knee_smoothness_db_,
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compression_ratio_)),
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knee_start_linear_(DbfsToFloatS16(knee_start_dbfs_)),
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limiter_start_dbfs_(knee_start_dbfs_ + knee_smoothness_db_),
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limiter_start_linear_(DbfsToFloatS16(limiter_start_dbfs_)),
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knee_region_polynomial_(ComputeKneeRegionPolynomial(knee_start_dbfs_,
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knee_smoothness_db_,
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compression_ratio_)),
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gain_curve_limiter_d1_(
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ComputeLimiterD1(max_input_level_db_, compression_ratio_)),
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gain_curve_limiter_d2_(ComputeLimiterD2(compression_ratio_)),
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gain_curve_limiter_i1_(1.0 / compression_ratio_),
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gain_curve_limiter_i2_(ComputeLimiterI2(max_input_level_db_,
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compression_ratio_,
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gain_curve_limiter_i1_)) {
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static_assert(knee_smoothness_db_ > 0.0f, "");
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static_assert(compression_ratio_ > 1.0f, "");
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RTC_CHECK_GE(max_input_level_db_, knee_start_dbfs_ + knee_smoothness_db_);
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}
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constexpr double LimiterDbGainCurve::max_input_level_db_;
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constexpr double LimiterDbGainCurve::knee_smoothness_db_;
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constexpr double LimiterDbGainCurve::compression_ratio_;
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double LimiterDbGainCurve::GetOutputLevelDbfs(double input_level_dbfs) const {
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if (input_level_dbfs < knee_start_dbfs_) {
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return input_level_dbfs;
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} else if (input_level_dbfs < limiter_start_dbfs_) {
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return GetKneeRegionOutputLevelDbfs(input_level_dbfs);
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}
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return GetCompressorRegionOutputLevelDbfs(input_level_dbfs);
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}
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double LimiterDbGainCurve::GetGainLinear(double input_level_linear) const {
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if (input_level_linear < knee_start_linear_) {
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return 1.0;
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}
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return DbfsToFloatS16(
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GetOutputLevelDbfs(FloatS16ToDbfs(input_level_linear))) /
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input_level_linear;
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}
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// Computes the first derivative of GetGainLinear() in |x|.
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double LimiterDbGainCurve::GetGainFirstDerivativeLinear(double x) const {
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// Beyond-knee region only.
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RTC_CHECK_GE(x, limiter_start_linear_ - 1e-7 * kMaxAbsFloatS16Value);
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return gain_curve_limiter_d1_ *
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std::pow(x / kMaxAbsFloatS16Value, gain_curve_limiter_d2_);
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}
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// Computes the integral of GetGainLinear() in the range [x0, x1].
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double LimiterDbGainCurve::GetGainIntegralLinear(double x0, double x1) const {
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RTC_CHECK_LE(x0, x1); // Valid interval.
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RTC_CHECK_GE(x0, limiter_start_linear_); // Beyond-knee region only.
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auto limiter_integral = [this](const double& x) {
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return gain_curve_limiter_i2_ * std::pow(x, gain_curve_limiter_i1_);
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};
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return limiter_integral(x1) - limiter_integral(x0);
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}
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double LimiterDbGainCurve::GetKneeRegionOutputLevelDbfs(
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double input_level_dbfs) const {
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return knee_region_polynomial_[0] * input_level_dbfs * input_level_dbfs +
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knee_region_polynomial_[1] * input_level_dbfs +
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knee_region_polynomial_[2];
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}
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double LimiterDbGainCurve::GetCompressorRegionOutputLevelDbfs(
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double input_level_dbfs) const {
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return (input_level_dbfs - max_input_level_db_) / compression_ratio_;
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}
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} // namespace webrtc
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