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diff --git a/webrtc/modules/audio_processing/agc2/rnn_vad/auto_correlation.h b/webrtc/modules/audio_processing/agc2/rnn_vad/auto_correlation.h
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+/*
+ *  Copyright (c) 2019 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_PROCESSING_AGC2_RNN_VAD_AUTO_CORRELATION_H_
+#define MODULES_AUDIO_PROCESSING_AGC2_RNN_VAD_AUTO_CORRELATION_H_
+
+#include <memory>
+
+#include "api/array_view.h"
+#include "modules/audio_processing/agc2/rnn_vad/common.h"
+#include "modules/audio_processing/utility/pffft_wrapper.h"
+
+namespace webrtc {
+namespace rnn_vad {
+
+// Class to compute the auto correlation on the pitch buffer for a target pitch
+// interval.
+class AutoCorrelationCalculator {
+ public:
+  AutoCorrelationCalculator();
+  AutoCorrelationCalculator(const AutoCorrelationCalculator&) = delete;
+  AutoCorrelationCalculator& operator=(const AutoCorrelationCalculator&) =
+      delete;
+  ~AutoCorrelationCalculator();
+
+  // Computes the auto-correlation coefficients for a target pitch interval.
+  // |auto_corr| indexes are inverted lags.
+  void ComputeOnPitchBuffer(
+      rtc::ArrayView<const float, kBufSize12kHz> pitch_buf,
+      rtc::ArrayView<float, kNumInvertedLags12kHz> auto_corr);
+
+ private:
+  Pffft fft_;
+  std::unique_ptr<Pffft::FloatBuffer> tmp_;
+  std::unique_ptr<Pffft::FloatBuffer> X_;
+  std::unique_ptr<Pffft::FloatBuffer> H_;
+};
+
+}  // namespace rnn_vad
+}  // namespace webrtc
+
+#endif  // MODULES_AUDIO_PROCESSING_AGC2_RNN_VAD_AUTO_CORRELATION_H_