Improved AGC update scheme for the audio backend in Chrome

media/audio/cras/cras_input.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/cras/cras_input.h"
 
 #include <math.h>
 
 #include "base/basictypes.h"
 #include "base/bind.h"
@@ skipping 89 matching lines @@
 }
 
 void CrasInputStream::Start(AudioInputCallback* callback) {
   DCHECK(client_);
   DCHECK(callback);
 
   // If already playing, stop before re-starting.
   if (started_)
     return;
 
+  StartAgc();
+
   callback_ = callback;
   LOG(ERROR) << "Input Start";
 
   // Prepare |audio_format| and |stream_params| for the stream we
   // will create.
   cras_audio_format* audio_format = cras_audio_format_create(
       alsa_util::BitsToFormat(params_.bits_per_sample()),
       params_.sample_rate(),
       params_.channels());
   if (!audio_format) {
@@ skipping 42 matching lines @@
 
   started_ = true;
 }
 
 void CrasInputStream::Stop() {
   DCHECK(client_);
 
   if (!callback_ || !started_)
     return;
 
+  StopAgc();
+
   // Removing the stream from the client stops audio.
   cras_client_rm_stream(client_, stream_id_);
 
   audio_manager_->DecreaseActiveInputStreamCount();
 
   started_ = false;
 }
 
 // Static callback asking for samples.  Run on high priority thread.
 int CrasInputStream::SamplesReady(cras_client* client,
@@ skipping 33 matching lines @@
       latency_ts.tv_nsec / base::Time::kNanosecondsPerMicrosecond;
   double frames_latency =
       latency_usec * params_.sample_rate() / base::Time::kMicrosecondsPerSecond;
   unsigned int bytes_latency =
       static_cast<unsigned int>(frames_latency * bytes_per_frame_);
 
   // Update the AGC volume level once every second. Note that, |volume| is
   // also updated each time SetVolume() is called through IPC by the
   // render-side AGC.
   double normalized_volume = 0.0;
-  QueryAgcVolume(&normalized_volume);
+  GetAgcVolume(&normalized_volume);
 
   callback_->OnData(this,
                     buffer,
                     frames * bytes_per_frame_,
                     bytes_latency,
                     normalized_volume);
 }
 
 void CrasInputStream::NotifyStreamError(int err) {
   if (callback_)
@@ skipping 34 matching lines @@
 
 double CrasInputStream::GetVolumeRatioFromDecibels(double dB) const {
   return pow(10, dB / 20.0);
 }
 
 double CrasInputStream::GetDecibelsFromVolumeRatio(double volume_ratio) const {
   return 20 * log10(volume_ratio);
 }
 
 }  // namespace media