1 files changed, 119 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/audio_processing/aec3/echo_audibility.cc b/third_party/libwebrtc/modules/audio_processing/aec3/echo_audibility.cc
new file mode 100644
index 0000000000..142a33d5e0
--- /dev/null
+++ b/third_party/libwebrtc/modules/audio_processing/aec3/echo_audibility.cc
@@ -0,0 +1,119 @@
+/*
+ *  Copyright (c) 2018 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 "modules/audio_processing/aec3/echo_audibility.h"
+
+#include <algorithm>
+#include <cmath>
+#include <utility>
+#include <vector>
+
+#include "api/array_view.h"
+#include "modules/audio_processing/aec3/block_buffer.h"
+#include "modules/audio_processing/aec3/spectrum_buffer.h"
+#include "modules/audio_processing/aec3/stationarity_estimator.h"
+
+namespace webrtc {
+
+EchoAudibility::EchoAudibility(bool use_render_stationarity_at_init)
+    : use_render_stationarity_at_init_(use_render_stationarity_at_init) {
+  Reset();
+}
+
+EchoAudibility::~EchoAudibility() = default;
+
+void EchoAudibility::Update(const RenderBuffer& render_buffer,
+                            rtc::ArrayView<const float> average_reverb,
+                            int delay_blocks,
+                            bool external_delay_seen) {
+  UpdateRenderNoiseEstimator(render_buffer.GetSpectrumBuffer(),
+                             render_buffer.GetBlockBuffer(),
+                             external_delay_seen);
+
+  if (external_delay_seen || use_render_stationarity_at_init_) {
+    UpdateRenderStationarityFlags(render_buffer, average_reverb, delay_blocks);
+  }
+}
+
+void EchoAudibility::Reset() {
+  render_stationarity_.Reset();
+  non_zero_render_seen_ = false;
+  render_spectrum_write_prev_ = absl::nullopt;
+}
+
+void EchoAudibility::UpdateRenderStationarityFlags(
+    const RenderBuffer& render_buffer,
+    rtc::ArrayView<const float> average_reverb,
+    int min_channel_delay_blocks) {
+  const SpectrumBuffer& spectrum_buffer = render_buffer.GetSpectrumBuffer();
+  int idx_at_delay = spectrum_buffer.OffsetIndex(spectrum_buffer.read,
+                                                 min_channel_delay_blocks);
+
+  int num_lookahead = render_buffer.Headroom() - min_channel_delay_blocks + 1;
+  num_lookahead = std::max(0, num_lookahead);
+
+  render_stationarity_.UpdateStationarityFlags(spectrum_buffer, average_reverb,
+                                               idx_at_delay, num_lookahead);
+}
+
+void EchoAudibility::UpdateRenderNoiseEstimator(
+    const SpectrumBuffer& spectrum_buffer,
+    const BlockBuffer& block_buffer,
+    bool external_delay_seen) {
+  if (!render_spectrum_write_prev_) {
+    render_spectrum_write_prev_ = spectrum_buffer.write;
+    render_block_write_prev_ = block_buffer.write;
+    return;
+  }
+  int render_spectrum_write_current = spectrum_buffer.write;
+  if (!non_zero_render_seen_ && !external_delay_seen) {
+    non_zero_render_seen_ = !IsRenderTooLow(block_buffer);
+  }
+  if (non_zero_render_seen_) {
+    for (int idx = render_spectrum_write_prev_.value();
+         idx != render_spectrum_write_current;
+         idx = spectrum_buffer.DecIndex(idx)) {
+      render_stationarity_.UpdateNoiseEstimator(spectrum_buffer.buffer[idx]);
+    }
+  }
+  render_spectrum_write_prev_ = render_spectrum_write_current;
+}
+
+bool EchoAudibility::IsRenderTooLow(const BlockBuffer& block_buffer) {
+  const int num_render_channels =
+      static_cast<int>(block_buffer.buffer[0].NumChannels());
+  bool too_low = false;
+  const int render_block_write_current = block_buffer.write;
+  if (render_block_write_current == render_block_write_prev_) {
+    too_low = true;
+  } else {
+    for (int idx = render_block_write_prev_; idx != render_block_write_current;
+         idx = block_buffer.IncIndex(idx)) {
+      float max_abs_over_channels = 0.f;
+      for (int ch = 0; ch < num_render_channels; ++ch) {
+        rtc::ArrayView<const float, kBlockSize> block =
+            block_buffer.buffer[idx].View(/*band=*/0, /*channel=*/ch);
+        auto r = std::minmax_element(block.cbegin(), block.cend());
+        float max_abs_channel =
+            std::max(std::fabs(*r.first), std::fabs(*r.second));
+        max_abs_over_channels =
+            std::max(max_abs_over_channels, max_abs_channel);
+      }
+      if (max_abs_over_channels < 10.f) {
+        too_low = true;  // Discards all blocks if one of them is too low.
+        break;
+      }
+    }
+  }
+  render_block_write_prev_ = render_block_write_current;
+  return too_low;
+}
+
+}  // namespace webrtc