1 files changed, 75 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/audio_processing/aec3/dominant_nearend_detector.cc b/third_party/libwebrtc/modules/audio_processing/aec3/dominant_nearend_detector.cc
new file mode 100644
index 0000000000..40073cf615
--- /dev/null
+++ b/third_party/libwebrtc/modules/audio_processing/aec3/dominant_nearend_detector.cc
@@ -0,0 +1,75 @@
+/*
+ *  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/dominant_nearend_detector.h"
+
+#include <numeric>
+
+namespace webrtc {
+DominantNearendDetector::DominantNearendDetector(
+    const EchoCanceller3Config::Suppressor::DominantNearendDetection& config,
+    size_t num_capture_channels)
+    : enr_threshold_(config.enr_threshold),
+      enr_exit_threshold_(config.enr_exit_threshold),
+      snr_threshold_(config.snr_threshold),
+      hold_duration_(config.hold_duration),
+      trigger_threshold_(config.trigger_threshold),
+      use_during_initial_phase_(config.use_during_initial_phase),
+      num_capture_channels_(num_capture_channels),
+      trigger_counters_(num_capture_channels_),
+      hold_counters_(num_capture_channels_) {}
+
+void DominantNearendDetector::Update(
+    rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>>
+        nearend_spectrum,
+    rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>>
+        residual_echo_spectrum,
+    rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>>
+        comfort_noise_spectrum,
+    bool initial_state) {
+  nearend_state_ = false;
+
+  auto low_frequency_energy = [](rtc::ArrayView<const float> spectrum) {
+    RTC_DCHECK_LE(16, spectrum.size());
+    return std::accumulate(spectrum.begin() + 1, spectrum.begin() + 16, 0.f);
+  };
+
+  for (size_t ch = 0; ch < num_capture_channels_; ++ch) {
+    const float ne_sum = low_frequency_energy(nearend_spectrum[ch]);
+    const float echo_sum = low_frequency_energy(residual_echo_spectrum[ch]);
+    const float noise_sum = low_frequency_energy(comfort_noise_spectrum[ch]);
+
+    // Detect strong active nearend if the nearend is sufficiently stronger than
+    // the echo and the nearend noise.
+    if ((!initial_state || use_during_initial_phase_) &&
+        echo_sum < enr_threshold_ * ne_sum &&
+        ne_sum > snr_threshold_ * noise_sum) {
+      if (++trigger_counters_[ch] >= trigger_threshold_) {
+        // After a period of strong active nearend activity, flag nearend mode.
+        hold_counters_[ch] = hold_duration_;
+        trigger_counters_[ch] = trigger_threshold_;
+      }
+    } else {
+      // Forget previously detected strong active nearend activity.
+      trigger_counters_[ch] = std::max(0, trigger_counters_[ch] - 1);
+    }
+
+    // Exit nearend-state early at strong echo.
+    if (echo_sum > enr_exit_threshold_ * ne_sum &&
+        echo_sum > snr_threshold_ * noise_sum) {
+      hold_counters_[ch] = 0;
+    }
+
+    // Remain in any nearend mode for a certain duration.
+    hold_counters_[ch] = std::max(0, hold_counters_[ch] - 1);
+    nearend_state_ = nearend_state_ || hold_counters_[ch] > 0;
+  }
+}
+}  // namespace webrtc