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;
+  }
+}
+
+}  // namespace
+
+OutputSelector::OutputSelector() = default;
+
+OutputSelector::~OutputSelector() = default;
+
+void OutputSelector::FormLinearOutput(
+    rtc::ArrayView<const float> linear_aec_output,
+    rtc::ArrayView<float> capture) {
+  rtc::ArrayView<const float>& e_main = linear_aec_output;
+  rtc::ArrayView<float> y = capture;
+
+  float y2_sum =
+      std::accumulate(y.begin(), y.end(), 0.f,
+                      [](float a, float b) -> float { return a + b * b; });
+  float e2_main_sum =
+      std::accumulate(e_main.begin(), e_main.end(), 0.f,
+                      [](float a, float b) -> float { return a + b * b; });
+
+  bool subtractor_output_is_best = (y2_sum > e2_main_sum);
+

[aleloi, 2017/02/13 16:44:50]

Please make y2_sum, e2_main_sum, subtractor_output const

[peah-webrtc, 2017/02/20 07:37:17]

Done.

+  if (subtractor_output_is_best != use_subtractor_output_) {
+    if (++output_change_counter_ > 15) {
+      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());
+    }
+  } else {
+    output_change_counter_ = 0;
+
+    if (use_subtractor_output_) {
+      std::copy(e_main.begin(), e_main.end(), y.begin());
+    }
+  }
+}

[aleloi, 2017/02/13 16:44:50]

I think the control flow can be a little simplified here. WDYT about this
change:

if (is_best != sub_output) counter++
if (counter > 15) {
   sub_output=...;
   Transition(...);
   counter=0;
} else if (sub_output) copy(...);

[peah-webrtc, 2017/02/20 07:37:17]

Good point!

Done.

+
+}  // namespace webrtc