Add detection for repeated audio in capturing.

content/renderer/media/media_stream_audio_processor.cc

Index: content/renderer/media/media_stream_audio_processor.cc
diff --git a/content/renderer/media/media_stream_audio_processor.cc b/content/renderer/media/media_stream_audio_processor.cc
index 23547d1b2b6490331f28d0110284f523044e1d57..1bf82bce5db6c01f84c26f62bbb42c1538597331 100644
--- a/content/renderer/media/media_stream_audio_processor.cc
+++ b/content/renderer/media/media_stream_audio_processor.cc
@@ -29,6 +29,20 @@ using webrtc::NoiseSuppression;
 
 const int kAudioProcessingNumberOfChannels = 1;
 
+// Minimum duration of a repetition.

[Henrik Grunell, 2015/10/20 08:50:16]

Put these in the AudioRepetitionReporter class.

[minyue, 2015/10/23 12:05:23]

The class is not present any longer. We may put these to
MediaStreamAudioProcessor, but that will make the class messier.

+const int kMinLengthMs = 1;
+
+// The following variables defines the look back time of repetitions that will
+// be logged. The complexity of the detector is proportional to the number of
+// look back times we keep track.
+const int kMinLookbackTimeMs = 10;
+const int kMaxLookbackTimeMs = 200;
+const int kLookbackTimeStepMs = 10;
+
+// Maximum frames of any input chunk of audio. Input longer than |kMaxFrames|
+// won't cause any problem, and will only affect computational efficiency.
+const size_t kMaxFrames = 480;  // 10 ms * 48 kHz
+
 AudioProcessing::ChannelLayout MapLayout(media::ChannelLayout media_layout) {
   switch (media_layout) {
     case media::CHANNEL_LAYOUT_MONO:
@@ -251,6 +265,16 @@ MediaStreamAudioProcessor::MediaStreamAudioProcessor(
   // ensure that we do get the filter when we should.
   if (aec_dump_message_filter_.get())
     aec_dump_message_filter_->AddDelegate(this);
+
+  // Create and configure |audio_repetition_reporter_|.
+  std::vector<int> look_back_times;
+  for (int time = kMaxLookbackTimeMs; time >= kMinLookbackTimeMs;
+       time -= kLookbackTimeStepMs) {
+    look_back_times.push_back(time);
+  }
+  audio_repetition_reporter_.reset(
+      new AudioRepetitionReporter(kMinLengthMs, kMaxFrames, &look_back_times[0],
+                                  look_back_times.size()));
 }
 
 MediaStreamAudioProcessor::~MediaStreamAudioProcessor() {
@@ -296,6 +320,13 @@ bool MediaStreamAudioProcessor::ProcessAndConsumeData(
   if (!capture_fifo_->Consume(&process_bus, capture_delay))
     return false;
 
+  // Detect bit-exact repetition of audio present in the captured audio.
+  // We detect only one channel.
+  audio_repetition_reporter_->Detect(process_bus->bus()->channel(0),
+                                     process_bus->bus()->frames(),
+                                     1,  // number of channels
+                                     input_format_.sample_rate());
+
   // Use the process bus directly if audio processing is disabled.
   MediaStreamAudioBus* output_bus = process_bus;
   *new_volume = 0;
@@ -374,6 +405,21 @@ void MediaStreamAudioProcessor::OnIpcClosing() {
   aec_dump_message_filter_ = NULL;
 }
 
+MediaStreamAudioProcessor::AudioRepetitionReporter::AudioRepetitionReporter(
+    int min_length_ms, size_t max_frames, const int* look_back_times,
+    size_t num_look_back)
+    : AudioRepetitionDetector(min_length_ms, max_frames, look_back_times,
+                              num_look_back) {
+}
+
+void MediaStreamAudioProcessor::AudioRepetitionReporter::ReportRepetition(
+    int look_back_ms) {
+  UMA_HISTOGRAM_CUSTOM_COUNTS(
+      "Media.AudioCapturerRepetition", look_back_ms,
+      kMinLookbackTimeMs, kMaxLookbackTimeMs,
+      (kMaxLookbackTimeMs - kMinLookbackTimeMs) / kLookbackTimeStepMs + 1);
+}
+
 void MediaStreamAudioProcessor::OnPlayoutData(media::AudioBus* audio_bus,
                                               int sample_rate,
                                               int audio_delay_milliseconds) {