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/*
* Copyright (c) 2018 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "modules/audio_processing/agc2/interpolated_gain_curve.h"
#include <algorithm>
#include <iterator>
#include "absl/strings/string_view.h"
#include "modules/audio_processing/agc2/agc2_common.h"
#include "modules/audio_processing/logging/apm_data_dumper.h"
#include "rtc_base/checks.h"
#include "rtc_base/strings/string_builder.h"
namespace webrtc {
constexpr std::array<float, kInterpolatedGainCurveTotalPoints>
InterpolatedGainCurve::approximation_params_x_;
constexpr std::array<float, kInterpolatedGainCurveTotalPoints>
InterpolatedGainCurve::approximation_params_m_;
constexpr std::array<float, kInterpolatedGainCurveTotalPoints>
InterpolatedGainCurve::approximation_params_q_;
InterpolatedGainCurve::InterpolatedGainCurve(
ApmDataDumper* apm_data_dumper,
absl::string_view histogram_name_prefix)
: region_logger_(
(StringBuilder("WebRTC.Audio.")
<< histogram_name_prefix << ".FixedDigitalGainCurveRegion.Identity")
.str(),
(StringBuilder("WebRTC.Audio.")
<< histogram_name_prefix << ".FixedDigitalGainCurveRegion.Knee")
.str(),
(StringBuilder("WebRTC.Audio.")
<< histogram_name_prefix << ".FixedDigitalGainCurveRegion.Limiter")
.str(),
(StringBuilder("WebRTC.Audio.")
<< histogram_name_prefix
<< ".FixedDigitalGainCurveRegion.Saturation")
.str()),
apm_data_dumper_(apm_data_dumper) {}
InterpolatedGainCurve::~InterpolatedGainCurve() {
if (stats_.available) {
RTC_DCHECK(apm_data_dumper_);
apm_data_dumper_->DumpRaw("agc2_interp_gain_curve_lookups_identity",
stats_.look_ups_identity_region);
apm_data_dumper_->DumpRaw("agc2_interp_gain_curve_lookups_knee",
stats_.look_ups_knee_region);
apm_data_dumper_->DumpRaw("agc2_interp_gain_curve_lookups_limiter",
stats_.look_ups_limiter_region);
apm_data_dumper_->DumpRaw("agc2_interp_gain_curve_lookups_saturation",
stats_.look_ups_saturation_region);
region_logger_.LogRegionStats(stats_);
}
}
InterpolatedGainCurve::RegionLogger::RegionLogger(
absl::string_view identity_histogram_name,
absl::string_view knee_histogram_name,
absl::string_view limiter_histogram_name,
absl::string_view saturation_histogram_name)
: identity_histogram(
metrics::HistogramFactoryGetCounts(identity_histogram_name,
1,
10000,
50)),
knee_histogram(metrics::HistogramFactoryGetCounts(knee_histogram_name,
1,
10000,
50)),
limiter_histogram(
metrics::HistogramFactoryGetCounts(limiter_histogram_name,
1,
10000,
50)),
saturation_histogram(
metrics::HistogramFactoryGetCounts(saturation_histogram_name,
1,
10000,
50)) {}
InterpolatedGainCurve::RegionLogger::~RegionLogger() = default;
void InterpolatedGainCurve::RegionLogger::LogRegionStats(
const InterpolatedGainCurve::Stats& stats) const {
using Region = InterpolatedGainCurve::GainCurveRegion;
const int duration_s =
stats.region_duration_frames / (1000 / kFrameDurationMs);
switch (stats.region) {
case Region::kIdentity: {
if (identity_histogram) {
metrics::HistogramAdd(identity_histogram, duration_s);
}
break;
}
case Region::kKnee: {
if (knee_histogram) {
metrics::HistogramAdd(knee_histogram, duration_s);
}
break;
}
case Region::kLimiter: {
if (limiter_histogram) {
metrics::HistogramAdd(limiter_histogram, duration_s);
}
break;
}
case Region::kSaturation: {
if (saturation_histogram) {
metrics::HistogramAdd(saturation_histogram, duration_s);
}
break;
}
default: {
RTC_DCHECK_NOTREACHED();
}
}
}
void InterpolatedGainCurve::UpdateStats(float input_level) const {
stats_.available = true;
GainCurveRegion region;
if (input_level < approximation_params_x_[0]) {
stats_.look_ups_identity_region++;
region = GainCurveRegion::kIdentity;
} else if (input_level <
approximation_params_x_[kInterpolatedGainCurveKneePoints - 1]) {
stats_.look_ups_knee_region++;
region = GainCurveRegion::kKnee;
} else if (input_level < kMaxInputLevelLinear) {
stats_.look_ups_limiter_region++;
region = GainCurveRegion::kLimiter;
} else {
stats_.look_ups_saturation_region++;
region = GainCurveRegion::kSaturation;
}
if (region == stats_.region) {
++stats_.region_duration_frames;
} else {
region_logger_.LogRegionStats(stats_);
stats_.region_duration_frames = 0;
stats_.region = region;
}
}
// Looks up a gain to apply given a non-negative input level.
// The cost of this operation depends on the region in which `input_level`
// falls.
// For the identity and the saturation regions the cost is O(1).
// For the other regions, namely knee and limiter, the cost is
// O(2 + log2(`LightkInterpolatedGainCurveTotalPoints`), plus O(1) for the
// linear interpolation (one product and one sum).
float InterpolatedGainCurve::LookUpGainToApply(float input_level) const {
UpdateStats(input_level);
if (input_level <= approximation_params_x_[0]) {
// Identity region.
return 1.0f;
}
if (input_level >= kMaxInputLevelLinear) {
// Saturating lower bound. The saturing samples exactly hit the clipping
// level. This method achieves has the lowest harmonic distorsion, but it
// may reduce the amplitude of the non-saturating samples too much.
return 32768.f / input_level;
}
// Knee and limiter regions; find the linear piece index. Spelling
// out the complete type was the only way to silence both the clang
// plugin and the windows compilers.
std::array<float, kInterpolatedGainCurveTotalPoints>::const_iterator it =
std::lower_bound(approximation_params_x_.begin(),
approximation_params_x_.end(), input_level);
const size_t index = std::distance(approximation_params_x_.begin(), it) - 1;
RTC_DCHECK_LE(0, index);
RTC_DCHECK_LT(index, approximation_params_m_.size());
RTC_DCHECK_LE(approximation_params_x_[index], input_level);
if (index < approximation_params_m_.size() - 1) {
RTC_DCHECK_LE(input_level, approximation_params_x_[index + 1]);
}
// Piece-wise linear interploation.
const float gain = approximation_params_m_[index] * input_level +
approximation_params_q_[index];
RTC_DCHECK_LE(0.f, gain);
return gain;
}
} // namespace webrtc
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