1 files changed, 146 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/audio_processing/aec3/erl_estimator.cc b/third_party/libwebrtc/modules/audio_processing/aec3/erl_estimator.cc
new file mode 100644
index 0000000000..01cc33cb80
--- /dev/null
+++ b/third_party/libwebrtc/modules/audio_processing/aec3/erl_estimator.cc
@@ -0,0 +1,146 @@
+/*
+ *  Copyright (c) 2017 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/erl_estimator.h"
+
+#include <algorithm>
+#include <numeric>
+
+#include "rtc_base/checks.h"
+
+namespace webrtc {
+
+namespace {
+
+constexpr float kMinErl = 0.01f;
+constexpr float kMaxErl = 1000.f;
+
+}  // namespace
+
+ErlEstimator::ErlEstimator(size_t startup_phase_length_blocks_)
+    : startup_phase_length_blocks__(startup_phase_length_blocks_) {
+  erl_.fill(kMaxErl);
+  hold_counters_.fill(0);
+  erl_time_domain_ = kMaxErl;
+  hold_counter_time_domain_ = 0;
+}
+
+ErlEstimator::~ErlEstimator() = default;
+
+void ErlEstimator::Reset() {
+  blocks_since_reset_ = 0;
+}
+
+void ErlEstimator::Update(
+    const std::vector<bool>& converged_filters,
+    rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>> render_spectra,
+    rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>>
+        capture_spectra) {
+  const size_t num_capture_channels = converged_filters.size();
+  RTC_DCHECK_EQ(capture_spectra.size(), num_capture_channels);
+
+  // Corresponds to WGN of power -46 dBFS.
+  constexpr float kX2Min = 44015068.0f;
+
+  const auto first_converged_iter =
+      std::find(converged_filters.begin(), converged_filters.end(), true);
+  const bool any_filter_converged =
+      first_converged_iter != converged_filters.end();
+
+  if (++blocks_since_reset_ < startup_phase_length_blocks__ ||
+      !any_filter_converged) {
+    return;
+  }
+
+  // Use the maximum spectrum across capture and the maximum across render.
+  std::array<float, kFftLengthBy2Plus1> max_capture_spectrum_data;
+  std::array<float, kFftLengthBy2Plus1> max_capture_spectrum =
+      capture_spectra[/*channel=*/0];
+  if (num_capture_channels > 1) {
+    // Initialize using the first channel with a converged filter.
+    const size_t first_converged =
+        std::distance(converged_filters.begin(), first_converged_iter);
+    RTC_DCHECK_GE(first_converged, 0);
+    RTC_DCHECK_LT(first_converged, num_capture_channels);
+    max_capture_spectrum_data = capture_spectra[first_converged];
+
+    for (size_t ch = first_converged + 1; ch < num_capture_channels; ++ch) {
+      if (!converged_filters[ch]) {
+        continue;
+      }
+      for (size_t k = 0; k < kFftLengthBy2Plus1; ++k) {
+        max_capture_spectrum_data[k] =
+            std::max(max_capture_spectrum_data[k], capture_spectra[ch][k]);
+      }
+    }
+    max_capture_spectrum = max_capture_spectrum_data;
+  }
+
+  const size_t num_render_channels = render_spectra.size();
+  std::array<float, kFftLengthBy2Plus1> max_render_spectrum_data;
+  rtc::ArrayView<const float, kFftLengthBy2Plus1> max_render_spectrum =
+      render_spectra[/*channel=*/0];
+  if (num_render_channels > 1) {
+    std::copy(render_spectra[0].begin(), render_spectra[0].end(),
+              max_render_spectrum_data.begin());
+    for (size_t ch = 1; ch < num_render_channels; ++ch) {
+      for (size_t k = 0; k < kFftLengthBy2Plus1; ++k) {
+        max_render_spectrum_data[k] =
+            std::max(max_render_spectrum_data[k], render_spectra[ch][k]);
+      }
+    }
+    max_render_spectrum = max_render_spectrum_data;
+  }
+
+  const auto& X2 = max_render_spectrum;
+  const auto& Y2 = max_capture_spectrum;
+
+  // Update the estimates in a maximum statistics manner.
+  for (size_t k = 1; k < kFftLengthBy2; ++k) {
+    if (X2[k] > kX2Min) {
+      const float new_erl = Y2[k] / X2[k];
+      if (new_erl < erl_[k]) {
+        hold_counters_[k - 1] = 1000;
+        erl_[k] += 0.1f * (new_erl - erl_[k]);
+        erl_[k] = std::max(erl_[k], kMinErl);
+      }
+    }
+  }
+
+  std::for_each(hold_counters_.begin(), hold_counters_.end(),
+                [](int& a) { --a; });
+  std::transform(hold_counters_.begin(), hold_counters_.end(), erl_.begin() + 1,
+                 erl_.begin() + 1, [](int a, float b) {
+                   return a > 0 ? b : std::min(kMaxErl, 2.f * b);
+                 });
+
+  erl_[0] = erl_[1];
+  erl_[kFftLengthBy2] = erl_[kFftLengthBy2 - 1];
+
+  // Compute ERL over all frequency bins.
+  const float X2_sum = std::accumulate(X2.begin(), X2.end(), 0.0f);
+
+  if (X2_sum > kX2Min * X2.size()) {
+    const float Y2_sum = std::accumulate(Y2.begin(), Y2.end(), 0.0f);
+    const float new_erl = Y2_sum / X2_sum;
+    if (new_erl < erl_time_domain_) {
+      hold_counter_time_domain_ = 1000;
+      erl_time_domain_ += 0.1f * (new_erl - erl_time_domain_);
+      erl_time_domain_ = std::max(erl_time_domain_, kMinErl);
+    }
+  }
+
+  --hold_counter_time_domain_;
+  erl_time_domain_ = (hold_counter_time_domain_ > 0)
+                         ? erl_time_domain_
+                         : std::min(kMaxErl, 2.f * erl_time_domain_);
+}
+
+}  // namespace webrtc