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

media/audio/audio_power_monitor.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 "media/audio/audio_power_monitor.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/float_util.h"
 #include "base/logging.h"
 #include "base/time/time.h"
 #include "media/base/audio_bus.h"
 #include "media/base/vector_math.h"
 
 namespace media {
 
+static const float kTimeConstantInSec = 0.01f;
+
 AudioPowerMonitor::AudioPowerMonitor(
     int sample_rate, const base::TimeDelta& time_constant)
     : sample_weight_(
           1.0f - expf(-1.0f / (sample_rate * time_constant.InSecondsF()))) {
   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() {
 }
 
 void AudioPowerMonitor::Reset() {
   power_reading_ = average_power_ = 0.0f;
   clipped_reading_ = has_clipped_ = false;
 }
 
 void AudioPowerMonitor::Scan(const AudioBus& buffer, int num_frames) {
   DCHECK_LE(num_frames, buffer.frames());
@@ skipping 24 matching lines @@
   if (reading_lock_.Try()) {
     power_reading_ = average_power_;
     if (has_clipped_) {
       clipped_reading_ = true;
       has_clipped_ = false;
     }
     reading_lock_.Release();
   }
 }
 
+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_);
 
   // Convert power level to dBFS units, and pin it down to zero if it is
   // insignificantly small.
   const float kInsignificantPower = 1.0e-10f;  // -100 dBFS
   const float power_dbfs = power_reading_ < kInsignificantPower ? zero_power() :
       10.0f * log10f(power_reading_);
 
   const bool clipped = clipped_reading_;
   clipped_reading_ = false;
 
   return std::make_pair(power_dbfs, clipped);
 }
 
 }  // namespace media