1 files changed, 90 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/audio_processing/agc2/rnn_vad/features_extraction.cc b/third_party/libwebrtc/modules/audio_processing/agc2/rnn_vad/features_extraction.cc
new file mode 100644
index 0000000000..502023428d
--- /dev/null
+++ b/third_party/libwebrtc/modules/audio_processing/agc2/rnn_vad/features_extraction.cc
@@ -0,0 +1,90 @@
+/*
+ *  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/agc2/rnn_vad/features_extraction.h"
+
+#include <array>
+
+#include "modules/audio_processing/agc2/rnn_vad/lp_residual.h"
+#include "rtc_base/checks.h"
+
+namespace webrtc {
+namespace rnn_vad {
+namespace {
+
+// Computed as `scipy.signal.butter(N=2, Wn=60/24000, btype='highpass')`.
+constexpr BiQuadFilter::Config kHpfConfig24k{
+    {0.99446179f, -1.98892358f, 0.99446179f},
+    {-1.98889291f, 0.98895425f}};
+
+}  // namespace
+
+FeaturesExtractor::FeaturesExtractor(const AvailableCpuFeatures& cpu_features)
+    : use_high_pass_filter_(false),
+      hpf_(kHpfConfig24k),
+      pitch_buf_24kHz_(),
+      pitch_buf_24kHz_view_(pitch_buf_24kHz_.GetBufferView()),
+      lp_residual_(kBufSize24kHz),
+      lp_residual_view_(lp_residual_.data(), kBufSize24kHz),
+      pitch_estimator_(cpu_features),
+      reference_frame_view_(pitch_buf_24kHz_.GetMostRecentValuesView()) {
+  RTC_DCHECK_EQ(kBufSize24kHz, lp_residual_.size());
+  Reset();
+}
+
+FeaturesExtractor::~FeaturesExtractor() = default;
+
+void FeaturesExtractor::Reset() {
+  pitch_buf_24kHz_.Reset();
+  spectral_features_extractor_.Reset();
+  if (use_high_pass_filter_) {
+    hpf_.Reset();
+  }
+}
+
+bool FeaturesExtractor::CheckSilenceComputeFeatures(
+    rtc::ArrayView<const float, kFrameSize10ms24kHz> samples,
+    rtc::ArrayView<float, kFeatureVectorSize> feature_vector) {
+  // Pre-processing.
+  if (use_high_pass_filter_) {
+    std::array<float, kFrameSize10ms24kHz> samples_filtered;
+    hpf_.Process(samples, samples_filtered);
+    // Feed buffer with the pre-processed version of `samples`.
+    pitch_buf_24kHz_.Push(samples_filtered);
+  } else {
+    // Feed buffer with `samples`.
+    pitch_buf_24kHz_.Push(samples);
+  }
+  // Extract the LP residual.
+  float lpc_coeffs[kNumLpcCoefficients];
+  ComputeAndPostProcessLpcCoefficients(pitch_buf_24kHz_view_, lpc_coeffs);
+  ComputeLpResidual(lpc_coeffs, pitch_buf_24kHz_view_, lp_residual_view_);
+  // Estimate pitch on the LP-residual and write the normalized pitch period
+  // into the output vector (normalization based on training data stats).
+  pitch_period_48kHz_ = pitch_estimator_.Estimate(lp_residual_view_);
+  feature_vector[kFeatureVectorSize - 2] = 0.01f * (pitch_period_48kHz_ - 300);
+  // Extract lagged frames (according to the estimated pitch period).
+  RTC_DCHECK_LE(pitch_period_48kHz_ / 2, kMaxPitch24kHz);
+  auto lagged_frame = pitch_buf_24kHz_view_.subview(
+      kMaxPitch24kHz - pitch_period_48kHz_ / 2, kFrameSize20ms24kHz);
+  // Analyze reference and lagged frames checking if silence has been detected
+  // and write the feature vector.
+  return spectral_features_extractor_.CheckSilenceComputeFeatures(
+      reference_frame_view_, {lagged_frame.data(), kFrameSize20ms24kHz},
+      {feature_vector.data() + kNumLowerBands, kNumBands - kNumLowerBands},
+      {feature_vector.data(), kNumLowerBands},
+      {feature_vector.data() + kNumBands, kNumLowerBands},
+      {feature_vector.data() + kNumBands + kNumLowerBands, kNumLowerBands},
+      {feature_vector.data() + kNumBands + 2 * kNumLowerBands, kNumLowerBands},
+      &feature_vector[kFeatureVectorSize - 1]);
+}
+
+}  // namespace rnn_vad
+}  // namespace webrtc