Adds volume level measurements to the AudioInputController for low-latency clients

media/audio/audio_input_controller.cc

 // Copyright (c) 2012 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 "media/audio/audio_input_controller.h"
 
 #include "base/bind.h"
 #include "base/threading/thread_restrictions.h"
+#include "base/time/time.h"
 #include "media/base/limits.h"
 #include "media/base/scoped_histogram_timer.h"
 #include "media/base/user_input_monitor.h"
 
+using base::TimeDelta;
+
 namespace {
 const int kMaxInputChannels = 3;
 
 // TODO(henrika): remove usage of timers and add support for proper
 // notification of when the input device is removed.  This was originally added
 // to resolve http://crbug.com/79936 for Windows platforms.  This then caused
 // breakage (very hard to repro bugs!) on other platforms: See
 // http://crbug.com/226327 and http://crbug.com/230972.
 // See also that the timer has been disabled on Mac now due to
 // crbug.com/357501.
 const int kTimerResetIntervalSeconds = 1;
 // We have received reports that the timer can be too trigger happy on some
 // Mac devices and the initial timer interval has therefore been increased
 // from 1 second to 5 seconds.
 const int kTimerInitialIntervalSeconds = 5;
+
+// Time constant for AudioPowerMonitor.  See AudioPowerMonitor ctor comments for
+// semantics.  This value was arbitrarily chosen, but seems to work well.
+const int kPowerMeasurementTimeConstantMillis = 10;
+
+// Time between two successive measurements of audio power levels.
+const int kPowerMonitorLogIntervalMilliSeconds = 500;
 }
 
 namespace media {
 
 // static
 AudioInputController::Factory* AudioInputController::factory_ = NULL;
 
 AudioInputController::AudioInputController(EventHandler* handler,
                                            SyncWriter* sync_writer,
                                            UserInputMonitor* user_input_monitor)
@@ skipping 128 matching lines @@
 void AudioInputController::SetAutomaticGainControl(bool enabled) {
   task_runner_->PostTask(FROM_HERE, base::Bind(
       &AudioInputController::DoSetAutomaticGainControl, this, enabled));
 }
 
 void AudioInputController::DoCreate(AudioManager* audio_manager,
                                     const AudioParameters& params,
                                     const std::string& device_id) {
   DCHECK(task_runner_->BelongsToCurrentThread());
   SCOPED_UMA_HISTOGRAM_TIMER("Media.AudioInputController.CreateTime");
+
+  // Create the audio (power) level meter given the provided audio parameters.
+  audio_level_.reset(new media::AudioPowerMonitor(params.sample_rate(),
+      TimeDelta::FromMilliseconds(kPowerMeasurementTimeConstantMillis)));
+  audio_bus_ = AudioBus::Create(params);
+  audio_params_ = params;
+
   // TODO(miu): See TODO at top of file.  Until that's resolved, assume all
   // platform audio input requires the |no_data_timer_| be used to auto-detect
   // errors.  In reality, probably only Windows needs to be treated as
   // unreliable here.
   DoCreateForStream(audio_manager->MakeAudioInputStream(params, device_id),
                     true);
 }
 
 void AudioInputController::DoCreateForStream(
     AudioInputStream* stream_to_control, bool enable_nodata_timer) {
@@ skipping 73 matching lines @@
 void AudioInputController::DoClose() {
   DCHECK(task_runner_->BelongsToCurrentThread());
   SCOPED_UMA_HISTOGRAM_TIMER("Media.AudioInputController.CloseTime");
 
   if (state_ == CLOSED)
     return;
 
   // Delete the timer on the same thread that created it.
   no_data_timer_.reset();
 
+  if (audio_level_)

[no longer working on chromium, 2014/05/19 15:15:48]

skip if

[henrika (OOO until Aug 14), 2014/05/19 15:25:46]

It can be NULL.

+    audio_level_->Reset();
+
   DoStopCloseAndClearStream();
   SetDataIsActive(false);
 
   if (SharedMemoryAndSyncSocketMode())
     sync_writer_->Close();
 
   if (user_input_monitor_)
     user_input_monitor_->DisableKeyPressMonitoring();
 
   state_ = CLOSED;
@@ skipping 91 matching lines @@
     key_pressed = current_count != prev_key_down_count_;
     prev_key_down_count_ = current_count;
     DVLOG_IF(6, key_pressed) << "Detected keypress.";
   }
 
   // Use SharedMemory and SyncSocket if the client has created a SyncWriter.
   // Used by all low-latency clients except WebSpeech.
   if (SharedMemoryAndSyncSocketMode()) {
     sync_writer_->Write(data, size, volume, key_pressed);
     sync_writer_->UpdateRecordedBytes(hardware_delay_bytes);
+
+    if (!audio_level_)

[no longer working on chromium, 2014/05/19 15:15:48]

can audio_level be NULL?

[henrika (OOO until Aug 14), 2014/05/19 15:25:46]

Yes, using new ctor. I can modify and create when needed instead.

+      return;
+
+    // Perform periodic audio (power) level measurements.
+    if ((base::TimeTicks::Now() - last_audio_level_log_time_).InMilliseconds() >
+        kPowerMonitorLogIntervalMilliSeconds) {
+      last_audio_level_log_time_ = base::TimeTicks::Now();
+      audio_bus_->FromInterleaved(
+          data, audio_bus_->frames(), audio_params_.bits_per_sample() / 8);
+      audio_level_->Scan(*audio_bus_, audio_bus_->frames());
+      std::pair<float, bool> result = audio_level_->ReadCurrentPowerAndClip();
+
+      // Get the audible level in the range [0.0,1.0], where 0.0 means
+      // the audio signal is silent and 1.0 means it is at maximum volume.
+      float level_dbfs = result.first;
+      float level = 0;
+      static const float kSilenceThresholdDBFS = -72.24719896f;
+      if (level_dbfs < kSilenceThresholdDBFS)
+        level = 0.0f;
+      else if (level_dbfs > 0.0f)
+        level = 1.0f;
+      else
+        level = 1.0f - level_dbfs / kSilenceThresholdDBFS;
+      DVLOG(1) << "audio_level: " << level;
+
+      audio_level_->Reset();
+    }
+
     return;
   }
 
   // TODO(henrika): Investigate if we can avoid the extra copy here.
   // (see http://crbug.com/249316 for details). AFAIK, this scope is only
   // active for WebSpeech clients.
   scoped_ptr<uint8[]> audio_data(new uint8[size]);
   memcpy(audio_data.get(), data, size);
 
   // Ownership of the audio buffer will be with the callback until it is run,
@@ skipping 30 matching lines @@
 
 void AudioInputController::SetDataIsActive(bool enabled) {
   base::subtle::Release_Store(&data_is_active_, enabled);
 }
 
 bool AudioInputController::GetDataIsActive() {
   return (base::subtle::Acquire_Load(&data_is_active_) != false);
 }
 
 }  // namespace media