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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/saturation_protector.h"
#include <memory>
#include "modules/audio_processing/agc2/agc2_common.h"
#include "modules/audio_processing/agc2/saturation_protector_buffer.h"
#include "modules/audio_processing/logging/apm_data_dumper.h"
#include "rtc_base/checks.h"
#include "rtc_base/numerics/safe_minmax.h"
namespace webrtc {
namespace {
constexpr int kPeakEnveloperSuperFrameLengthMs = 400;
constexpr float kMinMarginDb = 12.0f;
constexpr float kMaxMarginDb = 25.0f;
constexpr float kAttack = 0.9988493699365052f;
constexpr float kDecay = 0.9997697679981565f;
// Saturation protector state. Defined outside of `SaturationProtectorImpl` to
// implement check-point and restore ops.
struct SaturationProtectorState {
bool operator==(const SaturationProtectorState& s) const {
return headroom_db == s.headroom_db &&
peak_delay_buffer == s.peak_delay_buffer &&
max_peaks_dbfs == s.max_peaks_dbfs &&
time_since_push_ms == s.time_since_push_ms;
}
inline bool operator!=(const SaturationProtectorState& s) const {
return !(*this == s);
}
float headroom_db;
SaturationProtectorBuffer peak_delay_buffer;
float max_peaks_dbfs;
int time_since_push_ms; // Time since the last ring buffer push operation.
};
// Resets the saturation protector state.
void ResetSaturationProtectorState(float initial_headroom_db,
SaturationProtectorState& state) {
state.headroom_db = initial_headroom_db;
state.peak_delay_buffer.Reset();
state.max_peaks_dbfs = kMinLevelDbfs;
state.time_since_push_ms = 0;
}
// Updates `state` by analyzing the estimated speech level `speech_level_dbfs`
// and the peak level `peak_dbfs` for an observed frame. `state` must not be
// modified without calling this function.
void UpdateSaturationProtectorState(float peak_dbfs,
float speech_level_dbfs,
SaturationProtectorState& state) {
// Get the max peak over `kPeakEnveloperSuperFrameLengthMs` ms.
state.max_peaks_dbfs = std::max(state.max_peaks_dbfs, peak_dbfs);
state.time_since_push_ms += kFrameDurationMs;
if (rtc::SafeGt(state.time_since_push_ms, kPeakEnveloperSuperFrameLengthMs)) {
// Push `max_peaks_dbfs` back into the ring buffer.
state.peak_delay_buffer.PushBack(state.max_peaks_dbfs);
// Reset.
state.max_peaks_dbfs = kMinLevelDbfs;
state.time_since_push_ms = 0;
}
// Update the headroom by comparing the estimated speech level and the delayed
// max speech peak.
const float delayed_peak_dbfs =
state.peak_delay_buffer.Front().value_or(state.max_peaks_dbfs);
const float difference_db = delayed_peak_dbfs - speech_level_dbfs;
if (difference_db > state.headroom_db) {
// Attack.
state.headroom_db =
state.headroom_db * kAttack + difference_db * (1.0f - kAttack);
} else {
// Decay.
state.headroom_db =
state.headroom_db * kDecay + difference_db * (1.0f - kDecay);
}
state.headroom_db =
rtc::SafeClamp<float>(state.headroom_db, kMinMarginDb, kMaxMarginDb);
}
// Saturation protector which recommends a headroom based on the recent peaks.
class SaturationProtectorImpl : public SaturationProtector {
public:
explicit SaturationProtectorImpl(float initial_headroom_db,
int adjacent_speech_frames_threshold,
ApmDataDumper* apm_data_dumper)
: apm_data_dumper_(apm_data_dumper),
initial_headroom_db_(initial_headroom_db),
adjacent_speech_frames_threshold_(adjacent_speech_frames_threshold) {
Reset();
}
SaturationProtectorImpl(const SaturationProtectorImpl&) = delete;
SaturationProtectorImpl& operator=(const SaturationProtectorImpl&) = delete;
~SaturationProtectorImpl() = default;
float HeadroomDb() override { return headroom_db_; }
void Analyze(float speech_probability,
float peak_dbfs,
float speech_level_dbfs) override {
if (speech_probability < kVadConfidenceThreshold) {
// Not a speech frame.
if (adjacent_speech_frames_threshold_ > 1) {
// When two or more adjacent speech frames are required in order to
// update the state, we need to decide whether to discard or confirm the
// updates based on the speech sequence length.
if (num_adjacent_speech_frames_ >= adjacent_speech_frames_threshold_) {
// First non-speech frame after a long enough sequence of speech
// frames. Update the reliable state.
reliable_state_ = preliminary_state_;
} else if (num_adjacent_speech_frames_ > 0) {
// First non-speech frame after a too short sequence of speech frames.
// Reset to the last reliable state.
preliminary_state_ = reliable_state_;
}
}
num_adjacent_speech_frames_ = 0;
} else {
// Speech frame observed.
num_adjacent_speech_frames_++;
// Update preliminary level estimate.
UpdateSaturationProtectorState(peak_dbfs, speech_level_dbfs,
preliminary_state_);
if (num_adjacent_speech_frames_ >= adjacent_speech_frames_threshold_) {
// `preliminary_state_` is now reliable. Update the headroom.
headroom_db_ = preliminary_state_.headroom_db;
}
}
DumpDebugData();
}
void Reset() override {
num_adjacent_speech_frames_ = 0;
headroom_db_ = initial_headroom_db_;
ResetSaturationProtectorState(initial_headroom_db_, preliminary_state_);
ResetSaturationProtectorState(initial_headroom_db_, reliable_state_);
}
private:
void DumpDebugData() {
apm_data_dumper_->DumpRaw(
"agc2_saturation_protector_preliminary_max_peak_dbfs",
preliminary_state_.max_peaks_dbfs);
apm_data_dumper_->DumpRaw(
"agc2_saturation_protector_reliable_max_peak_dbfs",
reliable_state_.max_peaks_dbfs);
}
ApmDataDumper* const apm_data_dumper_;
const float initial_headroom_db_;
const int adjacent_speech_frames_threshold_;
int num_adjacent_speech_frames_;
float headroom_db_;
SaturationProtectorState preliminary_state_;
SaturationProtectorState reliable_state_;
};
} // namespace
std::unique_ptr<SaturationProtector> CreateSaturationProtector(
float initial_headroom_db,
int adjacent_speech_frames_threshold,
ApmDataDumper* apm_data_dumper) {
return std::make_unique<SaturationProtectorImpl>(
initial_headroom_db, adjacent_speech_frames_threshold, apm_data_dumper);
}
} // namespace webrtc
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