Add detection for repeated audio in capturing.

content/renderer/media/audio_repetition_detector_unittest.cc

Index: content/renderer/media/audio_repetition_detector_unittest.cc
diff --git a/content/renderer/media/audio_repetition_detector_unittest.cc b/content/renderer/media/audio_repetition_detector_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1e2a38865a9a663c81b910d82c2467f1e0fa7dff
--- /dev/null
+++ b/content/renderer/media/audio_repetition_detector_unittest.cc
@@ -0,0 +1,355 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <map>
+
+#include "base/macros.h"
+#include "base/rand_util.h"
+#include "content/renderer/media/audio_repetition_detector.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace content {
+
+class AudioRepetitionDetectorForTest : public AudioRepetitionDetector {
+ public:
+  int GetCount(int look_back_ms) {
+    auto it = counters_.find(look_back_ms);
+    if (it == counters_.end())
+      return 0;
+    return it->second;
+  }
+
+  void ResetCounters() {
+    counters_.clear();
+  }
+
+  void ResetLookbackTime(const int* look_back_times, size_t num) {
+    states_.clear();
+    for (size_t i = 0; i < num; ++i) {
+      RegisterLookbackTime(look_back_times[i]);
+    }
+  }
+
+  void set_max_frames(size_t max_frames) { max_frames_ = max_frames; }
+
+  void set_min_length_ms(int min_length_ms) { min_length_ms_ = min_length_ms; }
+
+ private:
+  void ReportRepetition(int look_back_ms) override {
+    auto it = counters_.find(look_back_ms);
+    if (it == counters_.end()) {
+      counters_.insert(std::pair<int, size_t>(look_back_ms, 1));
+      return;
+    }
+    it->second++;
+  }
+
+  std::map<int, size_t> counters_;
+};
+
+class AudioRepetitionDetectorTest : public ::testing::Test {
+ protected:
+  struct ExpectedCount {
+    int look_back_ms;
+    int count;
+  };
+
+  // Verify if the counts on the repetition patterns match expectation after
+  // injecting a signal. No reset on the counters
+  void Verify(const ExpectedCount* expected_counts, size_t num_patterns,
+              const float* tester, size_t num_frames,
+              int sample_rate_hz, size_t channels = 1) {
+    detector_.Detect(tester, num_frames, channels, sample_rate_hz);
+    for (size_t idx = 0; idx < num_patterns; ++idx) {
+      const int look_back_ms = expected_counts[idx].look_back_ms;
+      EXPECT_EQ(expected_counts[idx].count, detector_.GetCount(look_back_ms)) <<
+          "Repetition with look back " << look_back_ms << " ms counted wrong.";
+    }
+  }
+
+  void VerifyStereo(const ExpectedCount* expected_counts, size_t num_patterns,
+                    const float* tester, size_t num_frames,
+                    int sample_rate_hz) {
+    const size_t kNumChannels = 2;
+
+    // Get memory to store interleaved stereo.
+    scoped_ptr<float[]> tester_stereo(
+        new float[num_frames * kNumChannels]);
+
+    for (size_t idx = 0; idx < num_frames; ++idx, ++tester) {
+      for (size_t channel = 0; channel < kNumChannels; ++channel)
+        tester_stereo[idx * kNumChannels + channel] = *tester;
+    }
+
+    Verify(expected_counts, num_patterns, tester_stereo.get(),
+           num_frames, sample_rate_hz, kNumChannels);
+  }
+
+  void ResetLookbackTime(const int* look_back_times, size_t num) {
+    detector_.ResetLookbackTime(look_back_times, num);
+  }
+
+  void SetMaxFrames(size_t max_frames) {
+    detector_.set_max_frames(max_frames);
+  }
+
+  void SetMinLengthMs(int min_length_ms) {
+    detector_.set_min_length_ms(min_length_ms);
+  }
+
+  void ResetCounters() {
+    detector_.ResetCounters();
+  }
+
+ private:
+  AudioRepetitionDetectorForTest detector_;
+};
+
+TEST_F(AudioRepetitionDetectorTest, Basic) {
+  // To make the test signal most obvious, we choose a special sample rate.
+  const int kSampleRateHz = 1000;
+
+  // Check that one look back time will registered only once.
+  const int kLookbackTimes[] = {3, 3, 3, 3};
+
+  const float kTestSignal[] = {1, 2, 3, 1, 2, 3};
+  const ExpectedCount kExpectedCounts_1[] = {
+      {3, 1}
+  };
+  const ExpectedCount kExpectedCounts_2[] = {
+      {3, 1}
+  };
+
+  ResetLookbackTime(kLookbackTimes, arraysize(kLookbackTimes));
+  Verify(kExpectedCounts_1, arraysize(kExpectedCounts_1), kTestSignal,
+         arraysize(kTestSignal), kSampleRateHz);
+  Verify(kExpectedCounts_2, arraysize(kExpectedCounts_2), kTestSignal,
+         arraysize(kTestSignal), kSampleRateHz);
+  ResetCounters();
+
+  VerifyStereo(kExpectedCounts_1, arraysize(kExpectedCounts_1), kTestSignal,
+               arraysize(kTestSignal), kSampleRateHz);
+  VerifyStereo(kExpectedCounts_2, arraysize(kExpectedCounts_2), kTestSignal,
+               arraysize(kTestSignal), kSampleRateHz);
+}
+
+TEST_F(AudioRepetitionDetectorTest, StereoOutOfSync) {
+  // To make the test signal most obvious, we choose a special sample rate.
+  const int kSampleRateHz = 1000;
+
+  const int kLookbackTimes[] = {3};
+  const float kTestSignal[] = {
+      1, 1,
+      2, 2,
+      3, 3,
+      1, 1,
+      2, 2,
+      3, 1};
+  const ExpectedCount kExpectedCounts[] = {
+      {3, 0}
+  };
+
+  // By default, any repetition longer than 1 ms (1 sample at 1000 Hz) will be
+  // counted as repetition. This test needs to make it longer.
+  SetMinLengthMs(3);
+
+  ResetLookbackTime(kLookbackTimes, arraysize(kLookbackTimes));
+  Verify(kExpectedCounts, arraysize(kExpectedCounts), kTestSignal,
+         arraysize(kTestSignal) / 2, kSampleRateHz, 2);
+}
+
+TEST_F(AudioRepetitionDetectorTest, IncompletePattern) {
+  // To make the test signal most obvious, we choose a special sample rate.
+  const int kSampleRateHz = 1000;
+
+  const int kLookbackTimes[] = {3};
+  const float kTestSignal[] = {1, 2, 1, 2, 3, 1, 2, 3};
+  const ExpectedCount kExpectedCounts[] = {
+      {3, 1},
+  };
+
+  ResetLookbackTime(kLookbackTimes, arraysize(kLookbackTimes));
+  Verify(kExpectedCounts, arraysize(kExpectedCounts), kTestSignal,
+         arraysize(kTestSignal), kSampleRateHz);
+  ResetCounters();
+  VerifyStereo(kExpectedCounts, arraysize(kExpectedCounts), kTestSignal,
+               arraysize(kTestSignal), kSampleRateHz);
+}
+
+TEST_F(AudioRepetitionDetectorTest, PatternLongerThanFrame) {
+  // To make the test signal most obvious, we choose a special sample rate.
+  const int kSampleRateHz = 1000;
+
+  const int kLookbackTimes[] = {6};
+  const float kTestSignal_1[] = {1, 2, 3, 4, 5};
+  const float kTestSignal_2[] = {6, 1, 2, 3, 4, 5, 6};
+  const ExpectedCount kExpectedCounts_1[] = {
+      {6, 0},
+  };
+  const ExpectedCount kExpectedCounts_2[] = {
+      {6, 1},
+  };
+
+  ResetLookbackTime(kLookbackTimes, arraysize(kLookbackTimes));
+  Verify(kExpectedCounts_1, arraysize(kExpectedCounts_1), kTestSignal_1,
+         arraysize(kTestSignal_1), kSampleRateHz);
+  Verify(kExpectedCounts_2, arraysize(kExpectedCounts_2), kTestSignal_2,
+         arraysize(kTestSignal_2), kSampleRateHz);
+  ResetCounters();
+  VerifyStereo(kExpectedCounts_1, arraysize(kExpectedCounts_1), kTestSignal_1,
+               arraysize(kTestSignal_1), kSampleRateHz);
+  VerifyStereo(kExpectedCounts_2, arraysize(kExpectedCounts_2), kTestSignal_2,
+               arraysize(kTestSignal_2), kSampleRateHz);
+}
+
+TEST_F(AudioRepetitionDetectorTest, TwoPatterns) {
+  // To make the test signal most obvious, we choose a special sample rate.
+  const int kSampleRateHz = 1000;
+
+  const int kLookbackTimes[] = {3, 4};
+  const float kTestSignal[] = {1, 2, 3, 1, 2, 3, 4, 1, 2, 3, 4};
+  const ExpectedCount kExpectedCounts[] = {
+      // 1,2,3 belongs to both patterns.
+      {3, 1},
+      {4, 1}
+  };
+
+  ResetLookbackTime(kLookbackTimes, arraysize(kLookbackTimes));
+  Verify(kExpectedCounts, arraysize(kExpectedCounts), kTestSignal,
+         arraysize(kTestSignal), kSampleRateHz);
+  ResetCounters();
+  VerifyStereo(kExpectedCounts, arraysize(kExpectedCounts), kTestSignal,
+               arraysize(kTestSignal), kSampleRateHz);
+}
+
+TEST_F(AudioRepetitionDetectorTest, MaxFramesShorterThanInput) {
+  // To make the test signal most obvious, we choose a special sample rate.
+  const int kSampleRateHz = 1000;
+
+  const int kLookbackTimes[] = {3, 4};
+  const float kTestSignal[] = {1, 2, 3, 1, 2, 3, 4, 1, 2, 3, 4};
+  const ExpectedCount kExpectedCounts[] = {
+      // 1,2,3 belongs to both patterns.
+      {3, 1},
+      {4, 1}
+  };
+
+  // length of kTestSignal is 11 but I set maximum frames to be 2. The detection
+  // should still work.
+  SetMaxFrames(2);
+  ResetLookbackTime(kLookbackTimes, arraysize(kLookbackTimes));
+  Verify(kExpectedCounts, arraysize(kExpectedCounts), kTestSignal,
+         arraysize(kTestSignal), kSampleRateHz);
+  ResetCounters();
+  VerifyStereo(kExpectedCounts, arraysize(kExpectedCounts), kTestSignal,
+               arraysize(kTestSignal), kSampleRateHz);
+}
+
+TEST_F(AudioRepetitionDetectorTest, NestedPatterns) {
+  // To make the test signal most obvious, we choose a special sample rate.
+  const int kSampleRateHz = 1000;
+
+  const int kLookbackTimes[] = {6, 3};
+  const float kTestSignal[] = {1, 2, 3, 1, 2, 3};
+  const ExpectedCount kExpectedCounts_1[] = {
+      {3, 1},
+      {6, 0}
+  };
+  const ExpectedCount kExpectedCounts_2[] = {
+      {3, 1},
+      {6, 1}
+  };
+
+  ResetLookbackTime(kLookbackTimes, arraysize(kLookbackTimes));
+  Verify(kExpectedCounts_1, arraysize(kExpectedCounts_1), kTestSignal,
+         arraysize(kTestSignal), kSampleRateHz);
+  Verify(kExpectedCounts_2, arraysize(kExpectedCounts_2), kTestSignal,
+         arraysize(kTestSignal), kSampleRateHz);
+  ResetCounters();
+  VerifyStereo(kExpectedCounts_1, arraysize(kExpectedCounts_1), kTestSignal,
+               arraysize(kTestSignal), kSampleRateHz);
+  VerifyStereo(kExpectedCounts_2, arraysize(kExpectedCounts_2), kTestSignal,
+               arraysize(kTestSignal), kSampleRateHz);
+}
+
+TEST_F(AudioRepetitionDetectorTest, NotFullLengthPattern) {
+  // To make the test signal most obvious, we choose a special sample rate.
+  const int kSampleRateHz = 1000;
+
+  const int kLookbackTimes[] = {4};
+  const float kTestSignal[] = {1, 2, 3, -1, 1, 2, 3, -2};
+  const ExpectedCount kExpectedCounts[] = {
+      {4, 1},
+  };
+
+  ResetLookbackTime(kLookbackTimes, arraysize(kLookbackTimes));
+  Verify(kExpectedCounts, arraysize(kExpectedCounts), kTestSignal,
+         arraysize(kTestSignal), kSampleRateHz);
+  ResetCounters();
+  VerifyStereo(kExpectedCounts, arraysize(kExpectedCounts), kTestSignal,
+               arraysize(kTestSignal), kSampleRateHz);
+}
+
+TEST_F(AudioRepetitionDetectorTest, ZerosCountOrNot) {
+  // To make the test signal most obvious, we choose a special sample rate.
+  const int kSampleRateHz = 1000;
+
+  const int kLookbackTimes[] = {3};
+  const float kTestSignal_1[] = {0, 0, 0, 0, 0, 0};
+  const float kTestSignal_2[] = {0, 1, 2, 0, 1, 2};
+  const ExpectedCount kExpectedCounts_1[] = {
+      // Full zeros won't count.
+      {3, 0},
+  };
+  const ExpectedCount kExpectedCounts_2[] = {
+      // Partial zero will count.
+      {3, 1},
+  };
+
+  ResetLookbackTime(kLookbackTimes, arraysize(kLookbackTimes));
+  Verify(kExpectedCounts_1, arraysize(kExpectedCounts_1), kTestSignal_1,
+         arraysize(kTestSignal_1), kSampleRateHz);
+  Verify(kExpectedCounts_2, arraysize(kExpectedCounts_2), kTestSignal_2,
+         arraysize(kTestSignal_2), kSampleRateHz);
+  ResetCounters();
+  VerifyStereo(kExpectedCounts_1, arraysize(kExpectedCounts_1), kTestSignal_1,
+               arraysize(kTestSignal_1), kSampleRateHz);
+  VerifyStereo(kExpectedCounts_2, arraysize(kExpectedCounts_2), kTestSignal_2,
+               arraysize(kTestSignal_2), kSampleRateHz);
+}
+
+// Previous tests use short signal to test the detection algorithm, this one
+// tests the built-in pattern in AudioRepetitionDetector.
+TEST_F(AudioRepetitionDetectorTest, BuiltInPattern) {
+  const int kSampleRateHz = 44100;
+  // Let the signal be "*(4ms)-A(13ms)-*(100ms)-A", where * denotes random
+  // samples.
+  const size_t kPreSamples = kSampleRateHz * 4 / 1000;
+  const size_t kRepSamples = kSampleRateHz * 13 / 1000;
+  const size_t kSkipSamples = kSampleRateHz * 100 / 1000;
+  const size_t kSamples = kPreSamples + kRepSamples * 2 + kSkipSamples;
+
+  float test_signal[kSamples];
+  size_t idx = 0;
+  for (; idx < kPreSamples + kRepSamples + kSkipSamples; ++idx)
+    test_signal[idx] = static_cast<float>(base::RandDouble());
+
+  for (; idx < kSamples; ++idx)
+    test_signal[idx] = test_signal[idx - kSkipSamples];
+
+  // We currently track 20 look back times, 10, 20, 30, ..., 200.
+  ExpectedCount expect_counts[20];
+  for (int i = 0; i < 20; ++i) {
+    expect_counts[i].look_back_ms = (i + 1) * 10;
+    expect_counts[i].count = 0;
+  }
+
+  // We only expect a repetition with 100 ms look back time.
+  expect_counts[9].count = 1;
+
+  Verify(expect_counts, arraysize(expect_counts), test_signal, kSamples,
+         kSampleRateHz);
+}
+
+}  // namespace content