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diff --git a/third_party/libwebrtc/modules/audio_coding/neteq/expand.h b/third_party/libwebrtc/modules/audio_coding/neteq/expand.h
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+++ b/third_party/libwebrtc/modules/audio_coding/neteq/expand.h
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+/*
+ *  Copyright (c) 2012 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.
+ */
+
+#ifndef MODULES_AUDIO_CODING_NETEQ_EXPAND_H_
+#define MODULES_AUDIO_CODING_NETEQ_EXPAND_H_
+
+
+#include <memory>
+
+#include "modules/audio_coding/neteq/audio_vector.h"
+
+namespace webrtc {
+
+// Forward declarations.
+class AudioMultiVector;
+class BackgroundNoise;
+class RandomVector;
+class StatisticsCalculator;
+class SyncBuffer;
+
+// This class handles extrapolation of audio data from the sync_buffer to
+// produce packet-loss concealment.
+// TODO(hlundin): Refactor this class to divide the long methods into shorter
+// ones.
+class Expand {
+ public:
+  Expand(BackgroundNoise* background_noise,
+         SyncBuffer* sync_buffer,
+         RandomVector* random_vector,
+         StatisticsCalculator* statistics,
+         int fs,
+         size_t num_channels);
+
+  virtual ~Expand();
+
+  Expand(const Expand&) = delete;
+  Expand& operator=(const Expand&) = delete;
+
+  // Resets the object.
+  virtual void Reset();
+
+  // The main method to produce concealment data. The data is appended to the
+  // end of `output`.
+  virtual int Process(AudioMultiVector* output);
+
+  // Prepare the object to do extra expansion during normal operation following
+  // a period of expands.
+  virtual void SetParametersForNormalAfterExpand();
+
+  // Prepare the object to do extra expansion during merge operation following
+  // a period of expands.
+  virtual void SetParametersForMergeAfterExpand();
+
+  // Returns the mute factor for `channel`.
+  int16_t MuteFactor(size_t channel) const {
+    RTC_DCHECK_LT(channel, num_channels_);
+    return channel_parameters_[channel].mute_factor;
+  }
+
+  // Returns true if expansion has been faded down to zero amplitude (for all
+  // channels); false otherwise.
+  bool Muted() const;
+
+  // Accessors and mutators.
+  virtual size_t overlap_length() const;
+  size_t max_lag() const { return max_lag_; }
+
+ protected:
+  static const int kMaxConsecutiveExpands = 200;
+  void GenerateRandomVector(int16_t seed_increment,
+                            size_t length,
+                            int16_t* random_vector);
+
+  // Initializes member variables at the beginning of an expand period.
+  void InitializeForAnExpandPeriod();
+
+  bool TooManyExpands();
+
+  // Analyzes the signal history in `sync_buffer_`, and set up all parameters
+  // necessary to produce concealment data.
+  void AnalyzeSignal(int16_t* random_vector);
+
+  RandomVector* const random_vector_;
+  SyncBuffer* const sync_buffer_;
+  bool first_expand_;
+  const int fs_hz_;
+  const size_t num_channels_;
+  int consecutive_expands_;
+
+ private:
+  static const size_t kUnvoicedLpcOrder = 6;
+  static const size_t kNumCorrelationCandidates = 3;
+  static const size_t kDistortionLength = 20;
+  static const size_t kLpcAnalysisLength = 160;
+  static const size_t kMaxSampleRate = 48000;
+  static const int kNumLags = 3;
+
+  struct ChannelParameters {
+    ChannelParameters();
+    int16_t mute_factor;
+    int16_t ar_filter[kUnvoicedLpcOrder + 1];
+    int16_t ar_filter_state[kUnvoicedLpcOrder];
+    int16_t ar_gain;
+    int16_t ar_gain_scale;
+    int16_t voice_mix_factor;         /* Q14 */
+    int16_t current_voice_mix_factor; /* Q14 */
+    AudioVector expand_vector0;
+    AudioVector expand_vector1;
+    bool onset;
+    int mute_slope; /* Q20 */
+  };
+
+  // Calculate the auto-correlation of `input`, with length `input_length`
+  // samples. The correlation is calculated from a downsampled version of
+  // `input`, and is written to `output`.
+  void Correlation(const int16_t* input,
+                   size_t input_length,
+                   int16_t* output) const;
+
+  void UpdateLagIndex();
+
+  BackgroundNoise* const background_noise_;
+  StatisticsCalculator* const statistics_;
+  const size_t overlap_length_;
+  size_t max_lag_;
+  size_t expand_lags_[kNumLags];
+  int lag_index_direction_;
+  int current_lag_index_;
+  bool stop_muting_;
+  size_t expand_duration_samples_;
+  std::unique_ptr<ChannelParameters[]> channel_parameters_;
+};
+
+struct ExpandFactory {
+  ExpandFactory() {}
+  virtual ~ExpandFactory() {}
+
+  virtual Expand* Create(BackgroundNoise* background_noise,
+                         SyncBuffer* sync_buffer,
+                         RandomVector* random_vector,
+                         StatisticsCalculator* statistics,
+                         int fs,
+                         size_t num_channels) const;
+};
+
+}  // namespace webrtc
+#endif  // MODULES_AUDIO_CODING_NETEQ_EXPAND_H_