Adding audio RepetitionDetector in AudioProcessingModule.

webrtc/modules/audio_processing/repetition_detector.h

Index: webrtc/modules/audio_processing/repetition_detector.h
diff --git a/webrtc/modules/audio_processing/repetition_detector.h b/webrtc/modules/audio_processing/repetition_detector.h
new file mode 100644
index 0000000000000000000000000000000000000000..1a8b1535cd9daf77f5539ad12f36003329bf9f16
--- /dev/null
+++ b/webrtc/modules/audio_processing/repetition_detector.h
@@ -0,0 +1,108 @@
+/*
+ *  Copyright (c) 2015 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 WEBRTC_MODULES_AUDIO_PROCESSING_REPETITION_DETECTOR_H_
+#define WEBRTC_MODULES_AUDIO_PROCESSING_REPETITION_DETECTOR_H_
+
+#include <vector>
+
+#include "webrtc/base/constructormagic.h"
+#include "webrtc/base/scoped_ptr.h"
+#include "webrtc/system_wrappers/interface/scoped_vector.h"
+#include "webrtc/typedefs.h"
+
+namespace webrtc {
+
+class RepetitionDetectorForTest;
+
+class RepetitionDetector {
+ public:
+  RepetitionDetector();
+  virtual ~RepetitionDetector() {}
+
+  struct Pattern {
+    int id_;
+    // All followings are in milliseconds, since repetition patterns are
+    // supposedly bounded to certain duration in time.
+    int look_back_ms_;
+    int min_length_ms_;
+  };
+
+  // Detect repetition given audio samples. When multichannel, samples should be
+  // interleaved.
+  void Detect(const float* data, size_t num_frames, size_t num_channels,
+              int sample_rate_hz);
+
+  friend class RepetitionDetectorForTest;  // For testing.

[Andrew MacDonald, 2015/09/07 06:52:18]

Normally you'd use the FRIEND_TEST macro.

[minyue-webrtc, 2015/09/07 07:33:24]

Acknowledged.

[minyue-webrtc, 2015/09/11 14:01:41]

It turns out a bit complicated here.

RepetitionDetectorForTest is not Test, but an inherit of RepetitionDetector,
which defines ReportRepetition(). 

RepetitionDetectorTest is the actually test. 

FRIEND_TEST is used upon gTests, such RepetitionDetectorTest, but it is
RepetitionDetectorForTest that needs to access private members.

I liked to make RepetitionDetectorTest to inherit both RepetitionDetector and
::testing::Test, but henrik did not like it.

+
+ protected:
+  virtual void ReportRepetition(int id) { }

[Andrew MacDonald, 2015/09/07 06:52:18]

Why protected?

[minyue-webrtc, 2015/09/07 07:33:24]

true, not needed.

+
+ private:
+  class State {
+   public:
+    State(int id, int look_back_ms, int min_length_ms);
+
+    bool reported() const { return reported_; }
+    void set_reported(bool reported) { reported_ = reported; }
+
+    // Increase the counter by 1, and tell if the counted sample is zero.
+    void Increment(bool zero);
+
+    bool HasValidReport(int sample_rate_khz) const;
+
+    void Reset();
+    int id() const { return id_; }
+    int look_back_ms() const { return look_back_ms_; }
+
+   private:
+    const int id_;
+    const int look_back_ms_;
+    const int min_length_ms_;
+    size_t count_samples_;
+    bool all_zero_;
+    bool reported_;
+  };
+
+  // Register repetition patterns.
+  void RegisterRepetitionPatterns(const Pattern* patterns,
+                                  size_t num_patterns);
+
+  // Clear registered repetition patterns.
+  void ClearRepetitionPatterns();
+
+  // Reset |audio_buffer_| when number of channels or sample rate changes.
+  void Reset(size_t num_channels, int sample_rate_hz);
+
+  // Add sample (interleaved if stereo) to |audio_buffer_|.
+  void AddSampleToBuffer(const float* sample);
+
+  // Determine if a sample (interleaved if stereo) is identical to
+  // |audio_buffer_| at a look back position.
+  bool Equal(const float* sample, int look_back_samples) const;
+
+  // Determine if a sample (interleaved if stereo) is zero.
+  bool IsZero(const float* sample) const;
+
+  ScopedVector<State> states_;
+  int max_look_back_ms_;
+
+  rtc::scoped_ptr<float[]> audio_buffer_;  // Ring buffers to store input audio.
+  size_t num_channels_;  // Number of audio channels in buffer.
+  int sample_rate_hz_;  // Sample rate in kHz.
+  size_t buffer_size_samples_;  // Number of samples in |audio_buffer|.
+  size_t buffer_end_index_;  // The index of the last sample in |audio_buffer|.
+
+  DISALLOW_COPY_AND_ASSIGN(RepetitionDetector);
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_PROCESSING_REPETITION_DETECTOR_H_