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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/aec3/reverb_frequency_response.h"
#include <stddef.h>
#include <algorithm>
#include <array>
#include <numeric>
#include "api/array_view.h"
#include "modules/audio_processing/aec3/aec3_common.h"
#include "rtc_base/checks.h"
namespace webrtc {
namespace {
// Computes the ratio of the energies between the direct path and the tail. The
// energy is computed in the power spectrum domain discarding the DC
// contributions.
float AverageDecayWithinFilter(
rtc::ArrayView<const float> freq_resp_direct_path,
rtc::ArrayView<const float> freq_resp_tail) {
// Skipping the DC for the ratio computation
constexpr size_t kSkipBins = 1;
RTC_CHECK_EQ(freq_resp_direct_path.size(), freq_resp_tail.size());
float direct_path_energy =
std::accumulate(freq_resp_direct_path.begin() + kSkipBins,
freq_resp_direct_path.end(), 0.f);
if (direct_path_energy == 0.f) {
return 0.f;
}
float tail_energy = std::accumulate(freq_resp_tail.begin() + kSkipBins,
freq_resp_tail.end(), 0.f);
return tail_energy / direct_path_energy;
}
} // namespace
ReverbFrequencyResponse::ReverbFrequencyResponse() {
tail_response_.fill(0.f);
}
ReverbFrequencyResponse::~ReverbFrequencyResponse() = default;
void ReverbFrequencyResponse::Update(
const std::vector<std::array<float, kFftLengthBy2Plus1>>&
frequency_response,
int filter_delay_blocks,
const absl::optional<float>& linear_filter_quality,
bool stationary_block) {
if (stationary_block || !linear_filter_quality) {
return;
}
Update(frequency_response, filter_delay_blocks, *linear_filter_quality);
}
void ReverbFrequencyResponse::Update(
const std::vector<std::array<float, kFftLengthBy2Plus1>>&
frequency_response,
int filter_delay_blocks,
float linear_filter_quality) {
rtc::ArrayView<const float> freq_resp_tail(
frequency_response[frequency_response.size() - 1]);
rtc::ArrayView<const float> freq_resp_direct_path(
frequency_response[filter_delay_blocks]);
float average_decay =
AverageDecayWithinFilter(freq_resp_direct_path, freq_resp_tail);
const float smoothing = 0.2f * linear_filter_quality;
average_decay_ += smoothing * (average_decay - average_decay_);
for (size_t k = 0; k < kFftLengthBy2Plus1; ++k) {
tail_response_[k] = freq_resp_direct_path[k] * average_decay_;
}
for (size_t k = 1; k < kFftLengthBy2; ++k) {
const float avg_neighbour =
0.5f * (tail_response_[k - 1] + tail_response_[k + 1]);
tail_response_[k] = std::max(tail_response_[k], avg_neighbour);
}
}
} // namespace webrtc
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