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/*
* Copyright (c) 2019 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/alignment_mixer.h"
#include <algorithm>
#include "rtc_base/checks.h"
namespace webrtc {
namespace {
AlignmentMixer::MixingVariant ChooseMixingVariant(bool downmix,
bool adaptive_selection,
int num_channels) {
RTC_DCHECK(!(adaptive_selection && downmix));
RTC_DCHECK_LT(0, num_channels);
if (num_channels == 1) {
return AlignmentMixer::MixingVariant::kFixed;
}
if (downmix) {
return AlignmentMixer::MixingVariant::kDownmix;
}
if (adaptive_selection) {
return AlignmentMixer::MixingVariant::kAdaptive;
}
return AlignmentMixer::MixingVariant::kFixed;
}
} // namespace
AlignmentMixer::AlignmentMixer(
size_t num_channels,
const EchoCanceller3Config::Delay::AlignmentMixing& config)
: AlignmentMixer(num_channels,
config.downmix,
config.adaptive_selection,
config.activity_power_threshold,
config.prefer_first_two_channels) {}
AlignmentMixer::AlignmentMixer(size_t num_channels,
bool downmix,
bool adaptive_selection,
float activity_power_threshold,
bool prefer_first_two_channels)
: num_channels_(num_channels),
one_by_num_channels_(1.f / num_channels_),
excitation_energy_threshold_(kBlockSize * activity_power_threshold),
prefer_first_two_channels_(prefer_first_two_channels),
selection_variant_(
ChooseMixingVariant(downmix, adaptive_selection, num_channels_)) {
if (selection_variant_ == MixingVariant::kAdaptive) {
std::fill(strong_block_counters_.begin(), strong_block_counters_.end(), 0);
cumulative_energies_.resize(num_channels_);
std::fill(cumulative_energies_.begin(), cumulative_energies_.end(), 0.f);
}
}
void AlignmentMixer::ProduceOutput(const Block& x,
ArrayView<float, kBlockSize> y) {
RTC_DCHECK_EQ(x.NumChannels(), num_channels_);
if (selection_variant_ == MixingVariant::kDownmix) {
Downmix(x, y);
return;
}
int ch = selection_variant_ == MixingVariant::kFixed ? 0 : SelectChannel(x);
RTC_DCHECK_GT(x.NumChannels(), ch);
std::copy(x.begin(/*band=*/0, ch), x.end(/*band=*/0, ch), y.begin());
}
void AlignmentMixer::Downmix(const Block& x,
ArrayView<float, kBlockSize> y) const {
RTC_DCHECK_EQ(x.NumChannels(), num_channels_);
RTC_DCHECK_GE(num_channels_, 2);
std::memcpy(&y[0], x.View(/*band=*/0, /*channel=*/0).data(),
kBlockSize * sizeof(y[0]));
for (size_t ch = 1; ch < num_channels_; ++ch) {
const auto x_ch = x.View(/*band=*/0, ch);
for (size_t i = 0; i < kBlockSize; ++i) {
y[i] += x_ch[i];
}
}
for (size_t i = 0; i < kBlockSize; ++i) {
y[i] *= one_by_num_channels_;
}
}
int AlignmentMixer::SelectChannel(const Block& x) {
RTC_DCHECK_EQ(x.NumChannels(), num_channels_);
RTC_DCHECK_GE(num_channels_, 2);
RTC_DCHECK_EQ(cumulative_energies_.size(), num_channels_);
constexpr size_t kBlocksToChooseLeftOrRight =
static_cast<size_t>(0.5f * kNumBlocksPerSecond);
const bool good_signal_in_left_or_right =
prefer_first_two_channels_ &&
(strong_block_counters_[0] > kBlocksToChooseLeftOrRight ||
strong_block_counters_[1] > kBlocksToChooseLeftOrRight);
const int num_ch_to_analyze =
good_signal_in_left_or_right ? 2 : num_channels_;
constexpr int kNumBlocksBeforeEnergySmoothing = 60 * kNumBlocksPerSecond;
++block_counter_;
for (int ch = 0; ch < num_ch_to_analyze; ++ch) {
float x2_sum = 0.f;
ArrayView<const float, kBlockSize> x_ch = x.View(/*band=*/0, ch);
for (size_t i = 0; i < kBlockSize; ++i) {
x2_sum += x_ch[i] * x_ch[i];
}
if (ch < 2 && x2_sum > excitation_energy_threshold_) {
++strong_block_counters_[ch];
}
if (block_counter_ <= kNumBlocksBeforeEnergySmoothing) {
cumulative_energies_[ch] += x2_sum;
} else {
constexpr float kSmoothing = 1.f / (10 * kNumBlocksPerSecond);
cumulative_energies_[ch] +=
kSmoothing * (x2_sum - cumulative_energies_[ch]);
}
}
// Normalize the energies to allow the energy computations to from now be
// based on smoothing.
if (block_counter_ == kNumBlocksBeforeEnergySmoothing) {
constexpr float kOneByNumBlocksBeforeEnergySmoothing =
1.f / kNumBlocksBeforeEnergySmoothing;
for (int ch = 0; ch < num_ch_to_analyze; ++ch) {
cumulative_energies_[ch] *= kOneByNumBlocksBeforeEnergySmoothing;
}
}
int strongest_ch = 0;
for (int ch = 0; ch < num_ch_to_analyze; ++ch) {
if (cumulative_energies_[ch] > cumulative_energies_[strongest_ch]) {
strongest_ch = ch;
}
}
if ((good_signal_in_left_or_right && selected_channel_ > 1) ||
cumulative_energies_[strongest_ch] >
2.f * cumulative_energies_[selected_channel_]) {
selected_channel_ = strongest_ch;
}
return selected_channel_;
}
} // namespace webrtc
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