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      1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "content/renderer/media/webrtc_audio_capturer.h"
      6 
      7 #include "base/bind.h"
      8 #include "base/logging.h"
      9 #include "base/metrics/histogram.h"
     10 #include "base/strings/string_util.h"
     11 #include "base/strings/stringprintf.h"
     12 #include "content/child/child_process.h"
     13 #include "content/renderer/media/audio_device_factory.h"
     14 #include "content/renderer/media/media_stream_audio_processor.h"
     15 #include "content/renderer/media/media_stream_audio_processor_options.h"
     16 #include "content/renderer/media/media_stream_audio_source.h"
     17 #include "content/renderer/media/webrtc_audio_device_impl.h"
     18 #include "content/renderer/media/webrtc_local_audio_track.h"
     19 #include "content/renderer/media/webrtc_logging.h"
     20 #include "media/audio/sample_rates.h"
     21 
     22 namespace content {
     23 
     24 namespace {
     25 
     26 // Supported hardware sample rates for input and output sides.
     27 #if defined(OS_WIN) || defined(OS_MACOSX)
     28 // media::GetAudioInputHardwareSampleRate() asks the audio layer
     29 // for its current sample rate (set by the user) on Windows and Mac OS X.
     30 // The listed rates below adds restrictions and WebRtcAudioDeviceImpl::Init()
     31 // will fail if the user selects any rate outside these ranges.
     32 const int kValidInputRates[] =
     33     {192000, 96000, 48000, 44100, 32000, 16000, 8000};
     34 #elif defined(OS_LINUX) || defined(OS_OPENBSD)
     35 const int kValidInputRates[] = {48000, 44100};
     36 #elif defined(OS_ANDROID)
     37 const int kValidInputRates[] = {48000, 44100};
     38 #else
     39 const int kValidInputRates[] = {44100};
     40 #endif
     41 
     42 // Time constant for AudioPowerMonitor.  See AudioPowerMonitor ctor comments
     43 // for semantics.  This value was arbitrarily chosen, but seems to work well.
     44 const int kPowerMonitorTimeConstantMs = 10;
     45 
     46 // The time between two audio power level samples.
     47 const int kPowerMonitorLogIntervalSeconds = 10;
     48 
     49 }  // namespace
     50 
     51 // Reference counted container of WebRtcLocalAudioTrack delegate.
     52 // TODO(xians): Switch to MediaStreamAudioSinkOwner.
     53 class WebRtcAudioCapturer::TrackOwner
     54     : public base::RefCountedThreadSafe<WebRtcAudioCapturer::TrackOwner> {
     55  public:
     56   explicit TrackOwner(WebRtcLocalAudioTrack* track)
     57       : delegate_(track) {}
     58 
     59   void Capture(const int16* audio_data,
     60                base::TimeDelta delay,
     61                double volume,
     62                bool key_pressed,
     63                bool need_audio_processing) {
     64     base::AutoLock lock(lock_);
     65     if (delegate_) {
     66       delegate_->Capture(audio_data,
     67                          delay,
     68                          volume,
     69                          key_pressed,
     70                          need_audio_processing);
     71     }
     72   }
     73 
     74   void OnSetFormat(const media::AudioParameters& params) {
     75     base::AutoLock lock(lock_);
     76     if (delegate_)
     77       delegate_->OnSetFormat(params);
     78   }
     79 
     80   void SetAudioProcessor(
     81       const scoped_refptr<MediaStreamAudioProcessor>& processor) {
     82     base::AutoLock lock(lock_);
     83     if (delegate_)
     84       delegate_->SetAudioProcessor(processor);
     85   }
     86 
     87   void Reset() {
     88     base::AutoLock lock(lock_);
     89     delegate_ = NULL;
     90   }
     91 
     92   void Stop() {
     93     base::AutoLock lock(lock_);
     94     DCHECK(delegate_);
     95 
     96     // This can be reentrant so reset |delegate_| before calling out.
     97     WebRtcLocalAudioTrack* temp = delegate_;
     98     delegate_ = NULL;
     99     temp->Stop();
    100   }
    101 
    102   // Wrapper which allows to use std::find_if() when adding and removing
    103   // sinks to/from the list.
    104   struct TrackWrapper {
    105     TrackWrapper(WebRtcLocalAudioTrack* track) : track_(track) {}
    106     bool operator()(
    107         const scoped_refptr<WebRtcAudioCapturer::TrackOwner>& owner) const {
    108       return owner->IsEqual(track_);
    109     }
    110     WebRtcLocalAudioTrack* track_;
    111   };
    112 
    113  protected:
    114   virtual ~TrackOwner() {}
    115 
    116  private:
    117   friend class base::RefCountedThreadSafe<WebRtcAudioCapturer::TrackOwner>;
    118 
    119   bool IsEqual(const WebRtcLocalAudioTrack* other) const {
    120     base::AutoLock lock(lock_);
    121     return (other == delegate_);
    122   }
    123 
    124   // Do NOT reference count the |delegate_| to avoid cyclic reference counting.
    125   WebRtcLocalAudioTrack* delegate_;
    126   mutable base::Lock lock_;
    127 
    128   DISALLOW_COPY_AND_ASSIGN(TrackOwner);
    129 };
    130 
    131 // static
    132 scoped_refptr<WebRtcAudioCapturer> WebRtcAudioCapturer::CreateCapturer(
    133     int render_view_id, const StreamDeviceInfo& device_info,
    134     const blink::WebMediaConstraints& constraints,
    135     WebRtcAudioDeviceImpl* audio_device,
    136     MediaStreamAudioSource* audio_source) {
    137   scoped_refptr<WebRtcAudioCapturer> capturer = new WebRtcAudioCapturer(
    138       render_view_id, device_info, constraints, audio_device, audio_source);
    139   if (capturer->Initialize())
    140     return capturer;
    141 
    142   return NULL;
    143 }
    144 
    145 bool WebRtcAudioCapturer::Initialize() {
    146   DCHECK(thread_checker_.CalledOnValidThread());
    147   DVLOG(1) << "WebRtcAudioCapturer::Initialize()";
    148   WebRtcLogMessage(base::StringPrintf(
    149       "WAC::Initialize. render_view_id=%d"
    150       ", channel_layout=%d, sample_rate=%d, buffer_size=%d"
    151       ", session_id=%d, paired_output_sample_rate=%d"
    152       ", paired_output_frames_per_buffer=%d, effects=%d. ",
    153       render_view_id_,
    154       device_info_.device.input.channel_layout,
    155       device_info_.device.input.sample_rate,
    156       device_info_.device.input.frames_per_buffer,
    157       device_info_.session_id,
    158       device_info_.device.matched_output.sample_rate,
    159       device_info_.device.matched_output.frames_per_buffer,
    160       device_info_.device.input.effects));
    161 
    162   if (render_view_id_ == -1) {
    163     // Return true here to allow injecting a new source via
    164     // SetCapturerSourceForTesting() at a later state.
    165     return true;
    166   }
    167 
    168   MediaAudioConstraints audio_constraints(constraints_,
    169                                           device_info_.device.input.effects);
    170   if (!audio_constraints.IsValid())
    171     return false;
    172 
    173   media::ChannelLayout channel_layout = static_cast<media::ChannelLayout>(
    174       device_info_.device.input.channel_layout);
    175   DVLOG(1) << "Audio input hardware channel layout: " << channel_layout;
    176   UMA_HISTOGRAM_ENUMERATION("WebRTC.AudioInputChannelLayout",
    177                             channel_layout, media::CHANNEL_LAYOUT_MAX + 1);
    178 
    179   // Verify that the reported input channel configuration is supported.
    180   if (channel_layout != media::CHANNEL_LAYOUT_MONO &&
    181       channel_layout != media::CHANNEL_LAYOUT_STEREO &&
    182       channel_layout != media::CHANNEL_LAYOUT_STEREO_AND_KEYBOARD_MIC) {
    183     DLOG(ERROR) << channel_layout
    184                 << " is not a supported input channel configuration.";
    185     return false;
    186   }
    187 
    188   DVLOG(1) << "Audio input hardware sample rate: "
    189            << device_info_.device.input.sample_rate;
    190   media::AudioSampleRate asr;
    191   if (media::ToAudioSampleRate(device_info_.device.input.sample_rate, &asr)) {
    192     UMA_HISTOGRAM_ENUMERATION(
    193         "WebRTC.AudioInputSampleRate", asr, media::kAudioSampleRateMax + 1);
    194   } else {
    195     UMA_HISTOGRAM_COUNTS("WebRTC.AudioInputSampleRateUnexpected",
    196                          device_info_.device.input.sample_rate);
    197   }
    198 
    199   // Verify that the reported input hardware sample rate is supported
    200   // on the current platform.
    201   if (std::find(&kValidInputRates[0],
    202                 &kValidInputRates[0] + arraysize(kValidInputRates),
    203                 device_info_.device.input.sample_rate) ==
    204           &kValidInputRates[arraysize(kValidInputRates)]) {
    205     DLOG(ERROR) << device_info_.device.input.sample_rate
    206                 << " is not a supported input rate.";
    207     return false;
    208   }
    209 
    210   // Create and configure the default audio capturing source.
    211   SetCapturerSource(AudioDeviceFactory::NewInputDevice(render_view_id_),
    212                     channel_layout,
    213                     static_cast<float>(device_info_.device.input.sample_rate));
    214 
    215   // Add the capturer to the WebRtcAudioDeviceImpl since it needs some hardware
    216   // information from the capturer.
    217   if (audio_device_)
    218     audio_device_->AddAudioCapturer(this);
    219 
    220   return true;
    221 }
    222 
    223 WebRtcAudioCapturer::WebRtcAudioCapturer(
    224     int render_view_id,
    225     const StreamDeviceInfo& device_info,
    226     const blink::WebMediaConstraints& constraints,
    227     WebRtcAudioDeviceImpl* audio_device,
    228     MediaStreamAudioSource* audio_source)
    229     : constraints_(constraints),
    230       audio_processor_(
    231           new talk_base::RefCountedObject<MediaStreamAudioProcessor>(
    232               constraints, device_info.device.input.effects, audio_device)),
    233       running_(false),
    234       render_view_id_(render_view_id),
    235       device_info_(device_info),
    236       volume_(0),
    237       peer_connection_mode_(false),
    238       key_pressed_(false),
    239       need_audio_processing_(false),
    240       audio_device_(audio_device),
    241       audio_source_(audio_source),
    242       audio_power_monitor_(
    243           device_info_.device.input.sample_rate,
    244           base::TimeDelta::FromMilliseconds(kPowerMonitorTimeConstantMs)) {
    245   DVLOG(1) << "WebRtcAudioCapturer::WebRtcAudioCapturer()";
    246 }
    247 
    248 WebRtcAudioCapturer::~WebRtcAudioCapturer() {
    249   DCHECK(thread_checker_.CalledOnValidThread());
    250   DCHECK(tracks_.IsEmpty());
    251   DVLOG(1) << "WebRtcAudioCapturer::~WebRtcAudioCapturer()";
    252   Stop();
    253 }
    254 
    255 void WebRtcAudioCapturer::AddTrack(WebRtcLocalAudioTrack* track) {
    256   DCHECK(track);
    257   DVLOG(1) << "WebRtcAudioCapturer::AddTrack()";
    258 
    259   {
    260     base::AutoLock auto_lock(lock_);
    261     // Verify that |track| is not already added to the list.
    262     DCHECK(!tracks_.Contains(TrackOwner::TrackWrapper(track)));
    263 
    264     // Add with a tag, so we remember to call OnSetFormat() on the new
    265     // track.
    266     scoped_refptr<TrackOwner> track_owner(new TrackOwner(track));
    267     tracks_.AddAndTag(track_owner);
    268   }
    269 }
    270 
    271 void WebRtcAudioCapturer::RemoveTrack(WebRtcLocalAudioTrack* track) {
    272   DCHECK(thread_checker_.CalledOnValidThread());
    273   DVLOG(1) << "WebRtcAudioCapturer::RemoveTrack()";
    274   bool stop_source = false;
    275   {
    276     base::AutoLock auto_lock(lock_);
    277 
    278     scoped_refptr<TrackOwner> removed_item =
    279         tracks_.Remove(TrackOwner::TrackWrapper(track));
    280 
    281     // Clear the delegate to ensure that no more capture callbacks will
    282     // be sent to this sink. Also avoids a possible crash which can happen
    283     // if this method is called while capturing is active.
    284     if (removed_item.get()) {
    285       removed_item->Reset();
    286       stop_source = tracks_.IsEmpty();
    287     }
    288   }
    289   if (stop_source) {
    290     // Since WebRtcAudioCapturer does not inherit MediaStreamAudioSource,
    291     // and instead MediaStreamAudioSource is composed of a WebRtcAudioCapturer,
    292     // we have to call StopSource on the MediaStreamSource. This will call
    293     // MediaStreamAudioSource::DoStopSource which in turn call
    294     // WebRtcAudioCapturerer::Stop();
    295     audio_source_->StopSource();
    296   }
    297 }
    298 
    299 void WebRtcAudioCapturer::SetCapturerSource(
    300     const scoped_refptr<media::AudioCapturerSource>& source,
    301     media::ChannelLayout channel_layout,
    302     float sample_rate) {
    303   DCHECK(thread_checker_.CalledOnValidThread());
    304   DVLOG(1) << "SetCapturerSource(channel_layout=" << channel_layout << ","
    305            << "sample_rate=" << sample_rate << ")";
    306   scoped_refptr<media::AudioCapturerSource> old_source;
    307   {
    308     base::AutoLock auto_lock(lock_);
    309     if (source_.get() == source.get())
    310       return;
    311 
    312     source_.swap(old_source);
    313     source_ = source;
    314 
    315     // Reset the flag to allow starting the new source.
    316     running_ = false;
    317   }
    318 
    319   DVLOG(1) << "Switching to a new capture source.";
    320   if (old_source.get())
    321     old_source->Stop();
    322 
    323   // Dispatch the new parameters both to the sink(s) and to the new source,
    324   // also apply the new |constraints|.
    325   // The idea is to get rid of any dependency of the microphone parameters
    326   // which would normally be used by default.
    327   // bits_per_sample is always 16 for now.
    328   int buffer_size = GetBufferSize(sample_rate);
    329   media::AudioParameters params(media::AudioParameters::AUDIO_PCM_LOW_LATENCY,
    330                                 channel_layout, 0, sample_rate,
    331                                 16, buffer_size,
    332                                 device_info_.device.input.effects);
    333 
    334   {
    335     base::AutoLock auto_lock(lock_);
    336     // Notify the |audio_processor_| of the new format.
    337     audio_processor_->OnCaptureFormatChanged(params);
    338 
    339     MediaAudioConstraints audio_constraints(constraints_,
    340                                             device_info_.device.input.effects);
    341     need_audio_processing_ = audio_constraints.NeedsAudioProcessing();
    342     // Notify all tracks about the new format.
    343     tracks_.TagAll();
    344   }
    345 
    346   if (source.get())
    347     source->Initialize(params, this, session_id());
    348 
    349   Start();
    350 }
    351 
    352 void WebRtcAudioCapturer::EnablePeerConnectionMode() {
    353   DCHECK(thread_checker_.CalledOnValidThread());
    354   DVLOG(1) << "EnablePeerConnectionMode";
    355   // Do nothing if the peer connection mode has been enabled.
    356   if (peer_connection_mode_)
    357     return;
    358 
    359   peer_connection_mode_ = true;
    360   int render_view_id = -1;
    361   media::AudioParameters input_params;
    362   {
    363     base::AutoLock auto_lock(lock_);
    364     // Simply return if there is no existing source or the |render_view_id_| is
    365     // not valid.
    366     if (!source_.get() || render_view_id_== -1)
    367       return;
    368 
    369     render_view_id = render_view_id_;
    370     input_params = audio_processor_->InputFormat();
    371   }
    372 
    373   // Do nothing if the current buffer size is the WebRtc native buffer size.
    374   if (GetBufferSize(input_params.sample_rate()) ==
    375           input_params.frames_per_buffer()) {
    376     return;
    377   }
    378 
    379   // Create a new audio stream as source which will open the hardware using
    380   // WebRtc native buffer size.
    381   SetCapturerSource(AudioDeviceFactory::NewInputDevice(render_view_id),
    382                     input_params.channel_layout(),
    383                     static_cast<float>(input_params.sample_rate()));
    384 }
    385 
    386 void WebRtcAudioCapturer::Start() {
    387   DCHECK(thread_checker_.CalledOnValidThread());
    388   DVLOG(1) << "WebRtcAudioCapturer::Start()";
    389   base::AutoLock auto_lock(lock_);
    390   if (running_ || !source_)
    391     return;
    392 
    393   // Start the data source, i.e., start capturing data from the current source.
    394   // We need to set the AGC control before starting the stream.
    395   source_->SetAutomaticGainControl(true);
    396   source_->Start();
    397   running_ = true;
    398 }
    399 
    400 void WebRtcAudioCapturer::Stop() {
    401   DCHECK(thread_checker_.CalledOnValidThread());
    402   DVLOG(1) << "WebRtcAudioCapturer::Stop()";
    403   scoped_refptr<media::AudioCapturerSource> source;
    404   TrackList::ItemList tracks;
    405   {
    406     base::AutoLock auto_lock(lock_);
    407     if (!running_)
    408       return;
    409 
    410     source = source_;
    411     tracks = tracks_.Items();
    412     tracks_.Clear();
    413     running_ = false;
    414   }
    415 
    416   // Remove the capturer object from the WebRtcAudioDeviceImpl.
    417   if (audio_device_)
    418     audio_device_->RemoveAudioCapturer(this);
    419 
    420   for (TrackList::ItemList::const_iterator it = tracks.begin();
    421        it != tracks.end();
    422        ++it) {
    423     (*it)->Stop();
    424   }
    425 
    426   if (source.get())
    427     source->Stop();
    428 
    429   // Stop the audio processor to avoid feeding render data into the processor.
    430   audio_processor_->Stop();
    431 }
    432 
    433 void WebRtcAudioCapturer::SetVolume(int volume) {
    434   DVLOG(1) << "WebRtcAudioCapturer::SetVolume()";
    435   DCHECK_LE(volume, MaxVolume());
    436   double normalized_volume = static_cast<double>(volume) / MaxVolume();
    437   base::AutoLock auto_lock(lock_);
    438   if (source_.get())
    439     source_->SetVolume(normalized_volume);
    440 }
    441 
    442 int WebRtcAudioCapturer::Volume() const {
    443   base::AutoLock auto_lock(lock_);
    444   return volume_;
    445 }
    446 
    447 int WebRtcAudioCapturer::MaxVolume() const {
    448   return WebRtcAudioDeviceImpl::kMaxVolumeLevel;
    449 }
    450 
    451 void WebRtcAudioCapturer::Capture(const media::AudioBus* audio_source,
    452                                   int audio_delay_milliseconds,
    453                                   double volume,
    454                                   bool key_pressed) {
    455 // This callback is driven by AudioInputDevice::AudioThreadCallback if
    456 // |source_| is AudioInputDevice, otherwise it is driven by client's
    457 // CaptureCallback.
    458 #if defined(OS_WIN) || defined(OS_MACOSX)
    459   DCHECK_LE(volume, 1.0);
    460 #elif (defined(OS_LINUX) && !defined(OS_CHROMEOS)) || defined(OS_OPENBSD)
    461   // We have a special situation on Linux where the microphone volume can be
    462   // "higher than maximum". The input volume slider in the sound preference
    463   // allows the user to set a scaling that is higher than 100%. It means that
    464   // even if the reported maximum levels is N, the actual microphone level can
    465   // go up to 1.5x*N and that corresponds to a normalized |volume| of 1.5x.
    466   DCHECK_LE(volume, 1.6);
    467 #endif
    468 
    469   TrackList::ItemList tracks;
    470   TrackList::ItemList tracks_to_notify_format;
    471   int current_volume = 0;
    472   base::TimeDelta audio_delay;
    473   bool need_audio_processing = true;
    474   {
    475     base::AutoLock auto_lock(lock_);
    476     if (!running_)
    477       return;
    478 
    479     // Map internal volume range of [0.0, 1.0] into [0, 255] used by AGC.
    480     // The volume can be higher than 255 on Linux, and it will be cropped to
    481     // 255 since AGC does not allow values out of range.
    482     volume_ = static_cast<int>((volume * MaxVolume()) + 0.5);
    483     current_volume = volume_ > MaxVolume() ? MaxVolume() : volume_;
    484     audio_delay = base::TimeDelta::FromMilliseconds(audio_delay_milliseconds);
    485     audio_delay_ = audio_delay;
    486     key_pressed_ = key_pressed;
    487     tracks = tracks_.Items();
    488     tracks_.RetrieveAndClearTags(&tracks_to_notify_format);
    489 
    490     // Set the flag to turn on the audio processing in PeerConnection level.
    491     // Note that, we turn off the audio processing in PeerConnection if the
    492     // processor has already processed the data.
    493     need_audio_processing = need_audio_processing_ ?
    494         !MediaStreamAudioProcessor::IsAudioTrackProcessingEnabled() : false;
    495   }
    496 
    497   DCHECK(audio_processor_->InputFormat().IsValid());
    498   DCHECK_EQ(audio_source->channels(),
    499             audio_processor_->InputFormat().channels());
    500   DCHECK_EQ(audio_source->frames(),
    501             audio_processor_->InputFormat().frames_per_buffer());
    502 
    503   // Notify the tracks on when the format changes. This will do nothing if
    504   // |tracks_to_notify_format| is empty.
    505   media::AudioParameters output_params = audio_processor_->OutputFormat();
    506   for (TrackList::ItemList::const_iterator it = tracks_to_notify_format.begin();
    507        it != tracks_to_notify_format.end(); ++it) {
    508     (*it)->OnSetFormat(output_params);
    509     (*it)->SetAudioProcessor(audio_processor_);
    510   }
    511 
    512   if ((base::TimeTicks::Now() - last_audio_level_log_time_).InSeconds() >
    513           kPowerMonitorLogIntervalSeconds) {
    514     audio_power_monitor_.Scan(*audio_source, audio_source->frames());
    515 
    516     last_audio_level_log_time_ = base::TimeTicks::Now();
    517 
    518     std::pair<float, bool> result =
    519         audio_power_monitor_.ReadCurrentPowerAndClip();
    520     WebRtcLogMessage(base::StringPrintf(
    521         "WAC::Capture: current_audio_power=%.2fdBFS.", result.first));
    522 
    523     audio_power_monitor_.Reset();
    524   }
    525 
    526   // Push the data to the processor for processing.
    527   audio_processor_->PushCaptureData(audio_source);
    528 
    529   // Process and consume the data in the processor until there is not enough
    530   // data in the processor.
    531   int16* output = NULL;
    532   int new_volume = 0;
    533   while (audio_processor_->ProcessAndConsumeData(
    534       audio_delay, current_volume, key_pressed, &new_volume, &output)) {
    535     // Feed the post-processed data to the tracks.
    536     for (TrackList::ItemList::const_iterator it = tracks.begin();
    537          it != tracks.end(); ++it) {
    538       (*it)->Capture(output, audio_delay, current_volume, key_pressed,
    539                      need_audio_processing);
    540     }
    541 
    542     if (new_volume) {
    543       SetVolume(new_volume);
    544 
    545       // Update the |current_volume| to avoid passing the old volume to AGC.
    546       current_volume = new_volume;
    547     }
    548   }
    549 }
    550 
    551 void WebRtcAudioCapturer::OnCaptureError() {
    552   NOTIMPLEMENTED();
    553 }
    554 
    555 media::AudioParameters WebRtcAudioCapturer::source_audio_parameters() const {
    556   base::AutoLock auto_lock(lock_);
    557   return audio_processor_ ?
    558       audio_processor_->InputFormat() : media::AudioParameters();
    559 }
    560 
    561 bool WebRtcAudioCapturer::GetPairedOutputParameters(
    562     int* session_id,
    563     int* output_sample_rate,
    564     int* output_frames_per_buffer) const {
    565   // Don't set output parameters unless all of them are valid.
    566   if (device_info_.session_id <= 0 ||
    567       !device_info_.device.matched_output.sample_rate ||
    568       !device_info_.device.matched_output.frames_per_buffer)
    569     return false;
    570 
    571   *session_id = device_info_.session_id;
    572   *output_sample_rate = device_info_.device.matched_output.sample_rate;
    573   *output_frames_per_buffer =
    574       device_info_.device.matched_output.frames_per_buffer;
    575 
    576   return true;
    577 }
    578 
    579 int WebRtcAudioCapturer::GetBufferSize(int sample_rate) const {
    580   DCHECK(thread_checker_.CalledOnValidThread());
    581 #if defined(OS_ANDROID)
    582   // TODO(henrika): Tune and adjust buffer size on Android.
    583   return (2 * sample_rate / 100);
    584 #endif
    585 
    586   // PeerConnection is running at a buffer size of 10ms data. A multiple of
    587   // 10ms as the buffer size can give the best performance to PeerConnection.
    588   int peer_connection_buffer_size = sample_rate / 100;
    589 
    590   // Use the native hardware buffer size in non peer connection mode when the
    591   // platform is using a native buffer size smaller than the PeerConnection
    592   // buffer size.
    593   int hardware_buffer_size = device_info_.device.input.frames_per_buffer;
    594   if (!peer_connection_mode_ && hardware_buffer_size &&
    595       hardware_buffer_size <= peer_connection_buffer_size) {
    596     return hardware_buffer_size;
    597   }
    598 
    599   return (sample_rate / 100);
    600 }
    601 
    602 void WebRtcAudioCapturer::GetAudioProcessingParams(
    603     base::TimeDelta* delay, int* volume, bool* key_pressed) {
    604   base::AutoLock auto_lock(lock_);
    605   *delay = audio_delay_;
    606   *volume = volume_;
    607   *key_pressed = key_pressed_;
    608 }
    609 
    610 void WebRtcAudioCapturer::SetCapturerSourceForTesting(
    611     const scoped_refptr<media::AudioCapturerSource>& source,
    612     media::AudioParameters params) {
    613   // Create a new audio stream as source which uses the new source.
    614   SetCapturerSource(source, params.channel_layout(),
    615                     static_cast<float>(params.sample_rate()));
    616 }
    617 
    618 }  // namespace content
    619