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

media/audio/pulse/pulse_input.cc

Index: media/audio/pulse/pulse_input.cc
diff --git a/media/audio/pulse/pulse_input.cc b/media/audio/pulse/pulse_input.cc
index 9d31cddd735ff291713ae24c5e6e6f410008df8d..1e3fe0ee61d1b11e4550f1211415497fed610b1a 100644
--- a/media/audio/pulse/pulse_input.cc
+++ b/media/audio/pulse/pulse_input.cc
@@ -7,15 +7,19 @@
 #include <pulse/pulseaudio.h>
 
 #include "base/logging.h"
+#include "base/time/time.h"
 #include "media/audio/pulse/audio_manager_pulse.h"
 #include "media/audio/pulse/pulse_util.h"
 #include "media/base/seekable_buffer.h"
 
 namespace media {
 
+using base::TimeDelta;
 using pulse::AutoPulseLock;
 using pulse::WaitForOperationCompletion;
 
+static const int kPowerMeasurementTimeConstantMillis = 100;
+
 PulseAudioInputStream::PulseAudioInputStream(AudioManagerPulse* audio_manager,
                                              const std::string& device_name,
                                              const AudioParameters& params,
@@ -31,7 +35,8 @@ PulseAudioInputStream::PulseAudioInputStream(AudioManagerPulse* audio_manager,
       pa_mainloop_(mainloop),
       pa_context_(context),
       handle_(NULL),
-      context_state_changed_(false) {
+      context_state_changed_(false),
+      audio_level_monitor_(params) {
   DCHECK(mainloop);
   DCHECK(context);
 }
@@ -272,6 +277,21 @@ void PulseAudioInputStream::ReadData() {
   int packet_size = params_.GetBytesPerBuffer();
   while (buffer_->forward_bytes() >= packet_size) {
     buffer_->Read(audio_data_buffer_.get(), packet_size);
+
+    audio_level_monitor_.Scan(audio_data_buffer_.get(), packet_size);
+    std::pair<float, bool> result = audio_level_monitor_.ReadCurrentPowerAndClip();
+    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) << "PA audio_level: " << level;
+    audio_level_monitor_.Reset();
+
     callback_->OnData(this, audio_data_buffer_.get(), packet_size,
                       hardware_delay, normalized_volume);