Finalization of the first version of EchoCanceller 3

webrtc/modules/audio_processing/aec3/power_echo_model.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/power_echo_model.h"
+
+#include <string.h>
+#include <algorithm>
+
+#include "webrtc/base/optional.h"
+
+namespace webrtc {
+namespace {
+
+// Computes the spectral power over that last 20 frames.
+void RecentMaximum(const FftBuffer& X_buffer,
+                   std::array<float, kFftLengthBy2Plus1>* R2) {
+  R2->fill(0.f);
+  for (size_t j = 0; j < 20; ++j) {
+    std::transform(R2->begin(), R2->end(), X_buffer.Spectrum(j).begin(),
+                   R2->begin(),
+                   [](float a, float b) { return std::max(a, b); });
+  }
+}
+
+constexpr float kHInitial = 10.f;
+constexpr int kUpdateCounterInitial = 300;
+
+}  // namespace
+
+PowerEchoModel::PowerEchoModel() {
+  std::for_each(H2_.begin(), H2_.end(), [](CountedFloat& a) {

[ivoc, 2017/02/21 17:26:01]

Could this be replaced by a call to H2_->fill()?

[peah-webrtc, 2017/02/21 23:00:40]

Great suggestion!

That worked!!!

Done.

+    a = CountedFloat(kHInitial, kUpdateCounterInitial);
+  });
+}
+
+PowerEchoModel::~PowerEchoModel() = default;
+
+void PowerEchoModel::HandleEchoPathChange(
+    const EchoPathVariability& variability) {
+  if (variability.gain_change) {
+    std::for_each(H2_.begin(), H2_.end(), [](CountedFloat& a) {

[ivoc, 2017/02/21 17:26:01]

Same here?

[peah-webrtc, 2017/02/21 23:00:40]

Done.

+      a = CountedFloat(kHInitial, kUpdateCounterInitial);
+    });
+  }
+}
+
+void PowerEchoModel::EstimateEcho(
+    const FftBuffer& render_buffer,
+    const std::array<float, kFftLengthBy2Plus1>& capture_spectrum,
+    const AecState& aec_state,
+    std::array<float, kFftLengthBy2Plus1>* echo_spectrum) {
+  RTC_DCHECK(echo_spectrum);
+
+  const FftBuffer& X_buffer = render_buffer;
+  const std::array<float, kFftLengthBy2Plus1> Y2 = capture_spectrum;

[ivoc, 2017/02/21 17:26:01]

Is this necessary? it looks like the value of Y2 is not modified, so a reference
would be more efficient, right?

[peah-webrtc, 2017/02/21 23:00:40]

Ouch! That was a mistake! Good find. It should definitely be a reference.

Done.

+  std::array<float, kFftLengthBy2Plus1>* S2 = echo_spectrum;
+
+  // Choose delay to use.
+  const rtc::Optional<size_t> delay =
+      aec_state.FilterDelay()
+          ? aec_state.FilterDelay()
+          : (aec_state.ExternalDelay() ? rtc::Optional<size_t>(std::min<size_t>(
+                                             *aec_state.ExternalDelay(),
+                                             X_buffer.Buffer().size() - 1))
+                                       : rtc::Optional<size_t>());
+
+  // Compute R2.
+  std::array<float, kFftLengthBy2Plus1> render_max;
+  if (!delay) {
+    RecentMaximum(render_buffer, &render_max);
+  }
+  const std::array<float, kFftLengthBy2Plus1>& X2_active =
+      delay ? render_buffer.Spectrum(*delay) : render_max;
+
+  if (!aec_state.SaturatedCapture()) {
+    // Corresponds of WGN of power -46dBFS.
+    constexpr float kX2Min = 44015068.0f;
+    const int max_update_counter_value = delay ? 300 : 500;
+
+    std::array<float, kFftLengthBy2Plus1> new_H2;
+
+    // new_H2 = Y2 / X2.
+    std::transform(X2_active.begin(), X2_active.end(), Y2.begin(),
+                   new_H2.begin(),
+                   [&](float a, float b) { return a > kX2Min ? b / a : -1.f; });
+
+    // Lambda for updating H2 in a maximum statistics manner.
+    auto H2_updater = [&](float a, CountedFloat b) {
+      if (a > 0) {
+        if (a > b.value) {
+          b.counter = max_update_counter_value;
+          b.value = a;
+        } else if (--b.counter <= 0) {
+          b.value = std::max(b.value * 0.9f, 1.f);
+        }
+      }
+      return b;
+    };
+
+    std::transform(new_H2.begin(), new_H2.end(), H2_.begin(), H2_.begin(),
+                   H2_updater);
+  }
+
+  // S2 = H2*X2_active.
+  std::transform(H2_.begin(), H2_.end(), X2_active.begin(), S2->begin(),
+                 [](CountedFloat a, float b) { return a.value * b; });
+}
+
+}  // namespace webrtc