Add detection for repeated audio in capturing.

content/renderer/media/audio_repetition_detector_unittest.cc

+// 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/bind.h"
+#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 {
+
+namespace {
+const int kDefaultMinLengthMs = 1;
+const size_t kDefaultMaxFrames = 480;  // 10 ms * 48 kHz
+
+// Sample rate used in many tests. We choose a special sample rate in order to
+// make the test signal obvious.
+const int kSampleRateHz = 1000;
+
+}
+
+class AudioRepetitionDetectorForTest : public AudioRepetitionDetector {
+ public:
+  AudioRepetitionDetectorForTest(int min_length_ms, size_t max_frames,
+                                 const int* look_back_times,
+                                 size_t num_look_back)
+      : AudioRepetitionDetector(
+            min_length_ms, max_frames,
+            std::vector<int>(look_back_times, look_back_times + num_look_back),
+            base::Bind(&AudioRepetitionDetectorForTest::OnRepetitionDetected,
+                       base::Unretained(this))) {
+  }
+
+  int GetCount(int look_back_ms) const {
+    auto it = counters_.find(look_back_ms);
+    return it == counters_.end() ? 0 : it->second;
+  }
+
+  void ResetCounters() {
+    counters_.clear();
+  }
+
+ private:
+  void OnRepetitionDetected(int look_back_ms) {
+    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 {
+ public:
+  AudioRepetitionDetectorTest()
+      : detector_(nullptr) {
+  }
+
+ 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) {
+    static 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 SetDetector(int min_length_ms, size_t max_frames,
+                   const int* look_back_times, size_t num_look_back) {
+    detector_.reset(new AudioRepetitionDetectorForTest(min_length_ms,
+                                                       max_frames,
+                                                       look_back_times,
+                                                       num_look_back));
+  }
+
+  void ResetCounters() {
+    detector_->ResetCounters();
+  }
+
+ private:
+  scoped_ptr<AudioRepetitionDetectorForTest> detector_;
+};
+
+TEST_F(AudioRepetitionDetectorTest, Basic) {
+  // 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}
+  };
+
+
+  SetDetector(kDefaultMinLengthMs, kDefaultMaxFrames, 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) {
+  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.
+  SetDetector(3, kDefaultMaxFrames, kLookbackTimes, arraysize(kLookbackTimes));
+  Verify(kExpectedCounts, arraysize(kExpectedCounts), kTestSignal,
+         arraysize(kTestSignal) / 2, kSampleRateHz, 2);
+}
+
+TEST_F(AudioRepetitionDetectorTest, IncompletePattern) {
+  const int kLookbackTimes[] = {3};
+  const float kTestSignal[] = {1, 2, 1, 2, 3, 1, 2, 3};
+  const ExpectedCount kExpectedCounts[] = {
+      {3, 1},
+  };
+
+  SetDetector(kDefaultMinLengthMs, kDefaultMaxFrames, 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},
+  };
+
+  SetDetector(kDefaultMinLengthMs, kDefaultMaxFrames, 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) {
+  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}
+  };
+
+  SetDetector(kDefaultMinLengthMs, kDefaultMaxFrames, 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.
+  SetDetector(kDefaultMinLengthMs, 2, kLookbackTimes,arraysize(kLookbackTimes));
+  Verify(kExpectedCounts, arraysize(kExpectedCounts), kTestSignal,
+         arraysize(kTestSignal), kSampleRateHz);
+  ResetCounters();
+  VerifyStereo(kExpectedCounts, arraysize(kExpectedCounts), kTestSignal,
+               arraysize(kTestSignal), kSampleRateHz);
+}
+
+TEST_F(AudioRepetitionDetectorTest, NestedPatterns) {
+  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}
+  };
+
+  SetDetector(kDefaultMinLengthMs, kDefaultMaxFrames, 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) {
+  const int kLookbackTimes[] = {4};
+  const float kTestSignal[] = {1, 2, 3, -1, 1, 2, 3, -2};
+  const ExpectedCount kExpectedCounts[] = {
+      {4, 1},
+  };
+
+  SetDetector(kDefaultMinLengthMs, kDefaultMaxFrames, kLookbackTimes,
+              arraysize(kLookbackTimes));
+  Verify(kExpectedCounts, arraysize(kExpectedCounts), kTestSignal,
+         arraysize(kTestSignal), kSampleRateHz);
+  ResetCounters();
+  VerifyStereo(kExpectedCounts, arraysize(kExpectedCounts), kTestSignal,
+               arraysize(kTestSignal), kSampleRateHz);
+}
+
+TEST_F(AudioRepetitionDetectorTest, ZerosCountOrNot) {
+  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},
+  };
+
+  SetDetector(kDefaultMinLengthMs, kDefaultMaxFrames, 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 a normal frame size
+TEST_F(AudioRepetitionDetectorTest, NormalSignal) {
+  const int kNormalSampleRateHz = 44100;
+  // Let the signal be "*(4ms)-A(13ms)-*(100ms)-A", where * denotes random
+  // samples.
+  const size_t kPreSamples = kNormalSampleRateHz * 4 / 1000;
+  const size_t kRepSamples = kNormalSampleRateHz * 13 / 1000;
+  const size_t kSkipSamples = kNormalSampleRateHz * 100 / 1000;
+  const size_t kSamples = kPreSamples + kRepSamples * 2 + kSkipSamples;
+
+  const int kLookbackTimes[] = {80, 90, 100, 110, 120};
+
+  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];
+
+  ExpectedCount expect_counts[arraysize(kLookbackTimes)];
+  for (size_t i = 0; i < arraysize(kLookbackTimes); ++i) {
+    expect_counts[i].look_back_ms = kLookbackTimes[i];
+    expect_counts[i].count = 0;
+  }
+
+  // We only expect a repetition with 100 ms look back time.
+  expect_counts[2].count = 1;
+
+  SetDetector(kDefaultMinLengthMs, kDefaultMaxFrames, kLookbackTimes,
+              arraysize(kLookbackTimes));
+  Verify(expect_counts, arraysize(expect_counts), test_signal, kSamples,
+         kNormalSampleRateHz);
+}
+
+}  // namespace content