Finalization of the first version of EchoCanceller 3

webrtc/modules/audio_processing/aec3/render_signal_analyzer.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/render_signal_analyzer.h"
+
+#include <algorithm>
+
+#include "webrtc/base/checks.h"
+
+namespace webrtc {
+
+namespace {
+constexpr size_t kCounterThreshold = 5;
+
+}  // namespace
+
+RenderSignalAnalyzer::RenderSignalAnalyzer() {
+  narrow_band_counters_.fill(0);
+}
+RenderSignalAnalyzer::~RenderSignalAnalyzer() = default;
+
+void RenderSignalAnalyzer::Update(
+    const FftBuffer& X_buffer,
+    const rtc::Optional<size_t>& delay_partitions) {
+  if (!delay_partitions) {
+    narrow_band_counters_.fill(0);
+    return;
+  }
+
+  const std::array<float, kFftLengthBy2Plus1>& X2 =
+      X_buffer.Spectrum(*delay_partitions);
+
+  // Detect narrow band signal regions.
+  for (size_t k = 1; k < (X2.size() - 1); ++k) {
+    narrow_band_counters_[k - 1] = X2[k] > 3 * std::max(X2[k - 1], X2[k + 1])
+                                       ? narrow_band_counters_[k - 1] + 1
+                                       : 0;
+  }
+}
+
+void RenderSignalAnalyzer::MaskRegionsAroundNarrowBands(
+    std::array<float, kFftLengthBy2Plus1>* v) const {
+  RTC_DCHECK(v);
+
+  // Set v to zero around narrow band signal regions.
+  if (narrow_band_counters_[0] > kCounterThreshold) {
+    (*v)[1] = (*v)[0] = 0.f;
+  }
+  for (size_t k = 2; k < kFftLengthBy2 - 1; ++k) {
+    if (narrow_band_counters_[k - 1] > kCounterThreshold) {
+      (*v)[k - 2] = (*v)[k - 1] = (*v)[k] = (*v)[k + 1] = (*v)[k + 2] = 0.f;
+    }
+  }
+  if (narrow_band_counters_[kFftLengthBy2 - 2] > kCounterThreshold) {
+    (*v)[kFftLengthBy2] = (*v)[kFftLengthBy2 - 1] = 0.f;
+  }
+}
+
+}  // namespace webrtc