Finalization of the first version of EchoCanceller 3

webrtc/modules/audio_processing/aec3/erl_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/erl_estimator.h"
+
+#include <algorithm>
+
+namespace webrtc {
+
+namespace {
+
+constexpr float kMinErl = 0.01f;
+constexpr float kMaxErl = 1000.f;
+
+}  // namespace
+
+ErlEstimator::ErlEstimator() {
+  erl_.fill(kMaxErl);
+  hold_counters_.fill(0);
+}
+
+ErlEstimator::~ErlEstimator() = default;
+
+void ErlEstimator::Update(
+    const std::array<float, kFftLengthBy2Plus1>& render_spectrum,
+    const std::array<float, kFftLengthBy2Plus1>& capture_spectrum) {
+  const auto& X2 = render_spectrum;
+  const auto& Y2 = capture_spectrum;
+
+  // Corresponds to WGN of power -46 dBFS.
+  constexpr float kX2Min = 44015068.0f;
+
+  // Update the estimates in a maximum statistics manner.
+  for (size_t k = 1; k < kFftLengthBy2; ++k) {
+    if (X2[k] > kX2Min) {
+      const float new_erl = Y2[k] / X2[k];
+      if (new_erl < erl_[k]) {
+        hold_counters_[k - 1] = 1000;
+        erl_[k] += 0.1 * (new_erl - erl_[k]);
+        erl_[k] = std::max(erl_[k], kMinErl);
+      }
+    }
+  }
+
+  std::for_each(hold_counters_.begin(), hold_counters_.end(),
+                [](int& a) { --a; });
+  std::transform(hold_counters_.begin(), hold_counters_.end(), erl_.begin() + 1,
+                 erl_.begin() + 1, [](int a, float b) {
+                   return a > 0 ? b : std::min(kMaxErl, 2.f * b);
+                 });
+
+  erl_[0] = erl_[1];
+  erl_[kFftLengthBy2] = erl_[kFftLengthBy2 - 1];
+}
+
+}  // namespace webrtc