Improved AGC update scheme for the audio backend in Chrome

media/audio/linux/alsa_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/linux/alsa_input.h"
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop.h"
@@ skipping 84 matching lines @@
           wrapper_, mixer_handle_);
     }
   }
 
   return device_handle_ != NULL;
 }
 
 void AlsaPcmInputStream::Start(AudioInputCallback* callback) {
   DCHECK(!callback_ && callback);
   callback_ = callback;
+  StartAgc();
   int error = wrapper_->PcmPrepare(device_handle_);
   if (error < 0) {
     HandleError("PcmPrepare", error);
   } else {
     error = wrapper_->PcmStart(device_handle_);
     if (error < 0)
       HandleError("PcmStart", error);
   }
 
   if (error < 0) {
@@ skipping 81 matching lines @@
   }
 
   int num_buffers = frames / params_.frames_per_buffer();
   uint32 hardware_delay_bytes =
       static_cast<uint32>(GetCurrentDelay() * params_.GetBytesPerFrame());
   double normalized_volume = 0.0;
 
   // 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.
-  QueryAgcVolume(&normalized_volume);
+  GetAgcVolume(&normalized_volume);
 
   while (num_buffers--) {
     int frames_read = wrapper_->PcmReadi(device_handle_, audio_buffer_.get(),
                                          params_.frames_per_buffer());
     if (frames_read == params_.frames_per_buffer()) {
       callback_->OnData(this, audio_buffer_.get(), bytes_per_buffer_,
                         hardware_delay_bytes, normalized_volume);
     } else {
       LOG(WARNING) << "PcmReadi returning less than expected frames: "
                    << frames_read << " vs. " << params_.frames_per_buffer()
@@ skipping 16 matching lines @@
   base::MessageLoop::current()->PostDelayedTask(
       FROM_HERE,
       base::Bind(&AlsaPcmInputStream::ReadAudio, weak_factory_.GetWeakPtr()),
       delay);
 }
 
 void AlsaPcmInputStream::Stop() {
   if (!device_handle_ || !callback_)
     return;
 
+  StopAgc();
+
   // Stop is always called before Close. In case of error, this will be
   // also called when closing the input controller.
   audio_manager_->DecreaseActiveInputStreamCount();
 
   weak_factory_.InvalidateWeakPtrs();  // Cancel the next scheduled read.
   int error = wrapper_->PcmDrop(device_handle_);
   if (error < 0)
     HandleError("PcmDrop", error);
 }
 
@@ skipping 81 matching lines @@
 
   return static_cast<double>(current_volume);
 }
 
 void AlsaPcmInputStream::HandleError(const char* method, int error) {
   LOG(WARNING) << method << ": " << wrapper_->StrError(error);
   callback_->OnError(this);
 }
 
 }  // namespace media