Add detection for repeated audio in capturing.

content/renderer/media/media_stream_audio_processor.cc

 // Copyright 2013 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 "content/renderer/media/media_stream_audio_processor.h"
 
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 227 matching lines @@
   // True when |destination_| contains the data to be returned by the next call
   // to Consume().  Only used when the FIFO is disabled.
   bool data_available_;
 };
 
 MediaStreamAudioProcessor::MediaStreamAudioProcessor(
     const blink::WebMediaConstraints& constraints,
     const MediaStreamDevice::AudioDeviceParameters& input_params,
     WebRtcPlayoutDataSource* playout_data_source)
     : render_delay_ms_(0),
+      repetition_detector_(new RepetitionDetector()),
       playout_data_source_(playout_data_source),
       audio_mirroring_(false),
       typing_detected_(false),
       stopped_(false) {
   capture_thread_checker_.DetachFromThread();
   render_thread_checker_.DetachFromThread();
   InitializeAudioProcessingModule(constraints, input_params);
 
   aec_dump_message_filter_ = AecDumpMessageFilter::Get();
   // In unit tests not creating a message filter, |aec_dump_message_filter_|
@@ skipping 39 matching lines @@
   DCHECK(processed_data);
   DCHECK(capture_delay);
   DCHECK(new_volume);
 
   TRACE_EVENT0("audio", "MediaStreamAudioProcessor::ProcessAndConsumeData");
 
   MediaStreamAudioBus* process_bus;
   if (!capture_fifo_->Consume(&process_bus, capture_delay))
     return false;
 
+  // Detect if bit-exact repetition of audio present in the captured audio.

[Henrik Grunell, 2015/09/23 10:36:41]

Nit: "Detect bit-exact repetition of audio."

[minyue, 2015/09/25 14:40:06]

Done.

+  // We detect only one channel.
+  if (repetition_detector_) {
+    repetition_detector_->Detect(process_bus->bus()->channel(0),

[Henrik Grunell, 2015/09/23 06:54:15]

How much complexity does this add? Would be good to document that in the bug if
it isn't already.

How does the detector handle expected repetitions, like hooking a file or
generate a sinus directly to the input? (Will that be bit exact?)

[minyue, 2015/09/23 08:48:07]

It is O(n), n for number of samples. Each sample compares with the samples
sitting at the look back positions of the registered repetition patterns.

+                                 process_bus->bus()->frames(),
+                                 1,  // number of channels
+                                 input_format_.sample_rate());

[Henrik Grunell, 2015/09/23 06:54:15]

Does the |process_bus| contain the sample rate?

[minyue, 2015/09/23 08:48:07]

Unfortunately not. and that is why other places uses
input/output_format_.sample_rate() too, see, e.g.,

https://code.google.com/p/chromium/codesearch#chromium/src/content/renderer/m...

[Henrik Grunell, 2015/09/23 10:36:41]

I looked into this more. The MediaStreamAudioBus wraps an AudioBus which
contains all information needed. Let take a an AudioBus
RepetitionDetector::Detect(const AudioBus*)
and handle it there.

[minyue, 2015/09/25 14:40:06]

It is good for me to know that AudioBus has all info. and I can remove
input_format_ here. but I am a little bit against the idea of taking AudioBus as
input to Detect(). Since the detector is written a bit more general to accept
any number of channels, and it is up to the user to decide whether to check all
channels or only one (and which one).

+  }
+
   // Use the process bus directly if audio processing is disabled.
   MediaStreamAudioBus* output_bus = process_bus;
   *new_volume = 0;
   if (audio_processing_) {
     output_bus = output_bus_.get();
     *new_volume = ProcessData(process_bus->channel_ptrs(),
                               process_bus->bus()->frames(), *capture_delay,
                               volume, key_pressed, output_bus->channel_ptrs());
   }
 
@@ skipping 368 matching lines @@
   if (echo_information_) {
     echo_information_.get()->UpdateAecDelayStats(ap->echo_cancellation());
   }
 
   // Return 0 if the volume hasn't been changed, and otherwise the new volume.
   return (agc->stream_analog_level() == volume) ?
       0 : agc->stream_analog_level();
 }
 
 }  // namespace content