Finalization of the first version of EchoCanceller 3

webrtc/modules/audio_processing/aec3/output_selector.cc

+/*
+ *  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 "webrtc/modules/audio_processing/aec3/output_selector.h"
+
+#include <algorithm>
+#include <numeric>
+
+#include "webrtc/base/checks.h"
+
+namespace webrtc {
+namespace {
+
+// Performs the transition between the signals in a smooth manner.
+void SmoothFrameTransition(bool from_y_to_e,
+                           rtc::ArrayView<const float> e,
+                           rtc::ArrayView<float> y) {
+  RTC_DCHECK_LT(0u, e.size());
+  RTC_DCHECK_EQ(y.size(), e.size());
+
+  const float change_factor = (from_y_to_e ? 1.f : -1.f) / e.size();
+  float averaging = from_y_to_e ? 0.f : 1.f;
+  for (size_t k = 0; k < e.size(); ++k) {
+    y[k] += averaging * (e[k] - y[k]);
+    averaging += change_factor;
+  }
+  RTC_DCHECK_EQ(from_y_to_e ? 1.f : 0.f, averaging);
+}
+
+float BlockPower(rtc::ArrayView<const float> x) {
+  return std::accumulate(x.begin(), x.end(), 0.f,
+                         [](float a, float b) -> float { return a + b * b; });
+}
+
+}  // namespace
+
+OutputSelector::OutputSelector() = default;
+
+OutputSelector::~OutputSelector() = default;
+
+void OutputSelector::FormLinearOutput(
+    rtc::ArrayView<const float> subtractor_output,
+    rtc::ArrayView<float> capture) {
+  RTC_DCHECK_EQ(subtractor_output.size(), capture.size());
+  rtc::ArrayView<const float>& e_main = subtractor_output;
+  rtc::ArrayView<float> y = capture;
+
+  const bool subtractor_output_is_best =
+      BlockPower(y) > 1.5f * BlockPower(e_main);
+  output_change_counter_ = subtractor_output_is_best != use_subtractor_output_
+                               ? output_change_counter_ + 1
+                               : 0;
+
+  if (subtractor_output_is_best != use_subtractor_output_ &&
+      ((subtractor_output_is_best && output_change_counter_ > 3) ||
+       (!subtractor_output_is_best && output_change_counter_ > 10))) {
+    use_subtractor_output_ = subtractor_output_is_best;
+    SmoothFrameTransition(use_subtractor_output_, e_main, y);
+    output_change_counter_ = 0;
+  } else if (use_subtractor_output_) {
+    std::copy(e_main.begin(), e_main.end(), y.begin());
+  }
+}
+
+}  // namespace webrtc