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diff --git a/third_party/libwebrtc/modules/audio_coding/neteq/accelerate.h b/third_party/libwebrtc/modules/audio_coding/neteq/accelerate.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_ACCELERATE_H_
+#define MODULES_AUDIO_CODING_NETEQ_ACCELERATE_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "modules/audio_coding/neteq/time_stretch.h"
+
+namespace webrtc {
+
+class AudioMultiVector;
+class BackgroundNoise;
+
+// This class implements the Accelerate operation. Most of the work is done
+// in the base class TimeStretch, which is shared with the PreemptiveExpand
+// operation. In the Accelerate class, the operations that are specific to
+// Accelerate are implemented.
+class Accelerate : public TimeStretch {
+ public:
+  Accelerate(int sample_rate_hz,
+             size_t num_channels,
+             const BackgroundNoise& background_noise)
+      : TimeStretch(sample_rate_hz, num_channels, background_noise) {}
+
+  Accelerate(const Accelerate&) = delete;
+  Accelerate& operator=(const Accelerate&) = delete;
+
+  // This method performs the actual Accelerate operation. The samples are
+  // read from `input`, of length `input_length` elements, and are written to
+  // `output`. The number of samples removed through time-stretching is
+  // is provided in the output `length_change_samples`. The method returns
+  // the outcome of the operation as an enumerator value. If `fast_accelerate`
+  // is true, the algorithm will relax the requirements on finding strong
+  // correlations, and may remove multiple pitch periods if possible.
+  ReturnCodes Process(const int16_t* input,
+                      size_t input_length,
+                      bool fast_accelerate,
+                      AudioMultiVector* output,
+                      size_t* length_change_samples);
+
+ protected:
+  // Sets the parameters `best_correlation` and `peak_index` to suitable
+  // values when the signal contains no active speech.
+  void SetParametersForPassiveSpeech(size_t len,
+                                     int16_t* best_correlation,
+                                     size_t* peak_index) const override;
+
+  // Checks the criteria for performing the time-stretching operation and,
+  // if possible, performs the time-stretching.
+  ReturnCodes CheckCriteriaAndStretch(const int16_t* input,
+                                      size_t input_length,
+                                      size_t peak_index,
+                                      int16_t best_correlation,
+                                      bool active_speech,
+                                      bool fast_mode,
+                                      AudioMultiVector* output) const override;
+};
+
+struct AccelerateFactory {
+  AccelerateFactory() {}
+  virtual ~AccelerateFactory() {}
+
+  virtual Accelerate* Create(int sample_rate_hz,
+                             size_t num_channels,
+                             const BackgroundNoise& background_noise) const;
+};
+
+}  // namespace webrtc
+#endif  // MODULES_AUDIO_CODING_NETEQ_ACCELERATE_H_