Finalization of the first version of EchoCanceller 3

webrtc/modules/audio_processing/aec3/erle_estimator.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/erle_estimator.h"
+
+#include <algorithm>
+
+namespace webrtc {
+
+namespace {
+
+constexpr float kMinErle = 1.f;

[hlundin-webrtc, 2017/02/22 15:24:06]

In dB?

[peah-webrtc, 2017/02/22 23:51:38]

No, it is linear.

+constexpr float kMaxErle = 8.f;
+
+}  // namespace
+
+ErleEstimator::ErleEstimator() {
+  erle_.fill(kMinErle);
+  hold_counters_.fill(0);
+}
+
+ErleEstimator::~ErleEstimator() = default;
+
+void ErleEstimator::Update(
+    const std::array<float, kFftLengthBy2Plus1>& render_spectrum,
+    const std::array<float, kFftLengthBy2Plus1>& capture_spectrum,
+    const std::array<float, kFftLengthBy2Plus1>& subtractor_spectrum) {
+  const auto& X2 = render_spectrum;
+  const auto& Y2 = capture_spectrum;
+  const auto& E2 = subtractor_spectrum;
+
+  // Corresponds of WGN of power -46 dBFS.
+  const float kX2Min = 44015068.0f;

[hlundin-webrtc, 2017/02/22 15:24:06]

constexpr

[peah-webrtc, 2017/02/22 23:51:38]

Done.

+
+  // Update the estimates in a clamped minimum statistics manner.
+  for (size_t k = 1; k < kFftLengthBy2; ++k) {
+    if (X2[k] > kX2Min && E2[k] > 0.f) {
+      const float new_erle = Y2[k] / E2[k];
+      if (new_erle > erle_[k]) {
+        hold_counters_[k - 1] = 100;
+        erle_[k] += 0.1f * (new_erle - erle_[k]);
+        erle_[k] = std::max(kMinErle, std::min(erle_[k], kMaxErle));
+      }
+    }
+  }
+
+  std::for_each(hold_counters_.begin(), hold_counters_.end(),
+                [](int& a) { --a; });
+  std::transform(hold_counters_.begin(), hold_counters_.end(),
+                 erle_.begin() + 1, erle_.begin() + 1, [](int a, float b) {
+                   return a > 0 ? b : std::max(kMinErle, 0.97f * b);
+                 });
+
+  erle_[0] = erle_[1];
+  erle_[kFftLengthBy2] = erle_[kFftLengthBy2 - 1];
+}
+
+}  // namespace webrtc