fix the broeken audio for webrtc for precise

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 180 matching lines @@
     base::TimeDelta next_check_time = base::TimeDelta::FromMilliseconds(
         buffer_duration_ms_ / 2);
     MessageLoop::current()->PostDelayedTask(
         FROM_HERE,
         base::Bind(&AlsaPcmInputStream::ReadAudio, weak_factory_.GetWeakPtr()),
         next_check_time);
     return;
   }
 
   int num_buffers = frames / params_.frames_per_buffer();
-  int num_buffers_read = num_buffers;
   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);
 
   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()
                    << ". Dropping this buffer.";
     }
   }
 
-  next_read_time_ += base::TimeDelta::FromMilliseconds(
-      buffer_duration_ms_ * num_buffers_read);
+  next_read_time_ += base::TimeDelta::FromMilliseconds(buffer_duration_ms_);
   base::TimeDelta delay = next_read_time_ - base::Time::Now();
   if (delay < base::TimeDelta()) {
     LOG(WARNING) << "Audio read callback behind schedule by "
                  << (buffer_duration_ms_ - delay.InMilliseconds())
                  << " (ms).";
     // Read callback is behind schedule. Assuming there is data pending in
     // the soundcard, invoke the read callback immediate in order to catch up.
     read_callback_behind_schedule_ = true;
     delay = base::TimeDelta();
   }
@@ skipping 102 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, error);
 }
 
 }  // namespace media