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

media/audio/audio_power_monitor.cc

Index: media/audio/audio_power_monitor.cc
diff --git a/media/audio/audio_power_monitor.cc b/media/audio/audio_power_monitor.cc
index 6536f464b9c16905e7d4080a907b5a4df5678acf..d696ac9d2b9dbd9b684f564aa40c1633166052f0 100644
--- a/media/audio/audio_power_monitor.cc
+++ b/media/audio/audio_power_monitor.cc
@@ -15,6 +15,8 @@
 
 namespace media {
 
+static const float kTimeConstantInSec = 0.01f;
+
 AudioPowerMonitor::AudioPowerMonitor(
     int sample_rate, const base::TimeDelta& time_constant)
     : sample_weight_(
@@ -22,6 +24,13 @@ AudioPowerMonitor::AudioPowerMonitor(
   Reset();
 }
 
+AudioPowerMonitor::AudioPowerMonitor(const AudioParameters& params)
+  : sample_weight_(
+          1.0f - expf(-1.0f / (params.sample_rate() * kTimeConstantInSec))),

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

indentation.

+    audio_bus_(AudioBus::Create(params)),
+    params_(params) {
+}
+
 AudioPowerMonitor::~AudioPowerMonitor() {
 }
 
@@ -66,6 +75,13 @@ void AudioPowerMonitor::Scan(const AudioBus& buffer, int num_frames) {
   }
 }
 
+void AudioPowerMonitor::Scan(const void* data, uint32 size) {

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

Ideally we should not change this audio_power_monitor.cc, but change our input
code to work with AudioBus instead.

You'd better check with Dale if you want audio_power_minitor.cc to deal with
void*

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

It is a rather big change to do that for all platforms and I did not see it as
goal of this CL. I could add a TODO to remove this implementation once that has
been done. Sound OK?

+  DCHECK_EQ(static_cast<int>(size), params_.GetBytesPerBuffer());
+  audio_bus_->FromInterleaved(
+          data, audio_bus_->frames(), params_.bits_per_sample() / 8);
+  Scan(*audio_bus_, audio_bus_->frames());
+}
+
 std::pair<float, bool> AudioPowerMonitor::ReadCurrentPowerAndClip() {
   base::AutoLock for_reading(reading_lock_);