Add support for real-time audio threads.

content/renderer/audio_device.cc

 // Copyright (c) 2011 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 "content/renderer/audio_device.h"
 
 #include "base/memory/singleton.h"
 #include "base/message_loop.h"
 #include "content/common/audio_messages.h"
 #include "content/common/child_process.h"
@@ skipping 189 matching lines @@
 
   // TODO(crogers) : check that length is big enough for buffer_size_
 
   shared_memory_.reset(new base::SharedMemory(handle, false));
   shared_memory_->Map(length);
 
   socket_.reset(new base::SyncSocket(socket_handle));
   // Allow the client to pre-populate the buffer.
   FireRenderCallback();
 
-  // TODO(crogers): we could optionally set the thread to high-priority
   audio_thread_.reset(
       new base::DelegateSimpleThread(this, "renderer_audio_thread"));
   audio_thread_->Start();
 
   if (filter_) {
     filter_->message_loop()->PostTask(FROM_HERE,
         NewRunnableMethod(this, &AudioDevice::StartOnIOThread));
   }
 }
 
 void AudioDevice::OnVolume(double volume) {
   NOTIMPLEMENTED();
 }
 
 // Our audio thread runs here.
 void AudioDevice::Run() {
+    audio_thread_->SetThreadPriority(base::kThreadPriority_RealtimeAudio);
+
   int pending_data;
   const int samples_per_ms = static_cast<int>(sample_rate_) / 1000;
   const int bytes_per_ms = channels_ * (bits_per_sample_ / 8) * samples_per_ms;
 
   while (sizeof(pending_data) == socket_->Receive(&pending_data,
                                                   sizeof(pending_data)) &&
                                                   pending_data >= 0) {
     {
       // Convert the number of pending bytes in the render buffer
       // into milliseconds.
       audio_delay_milliseconds_ = pending_data / bytes_per_ms;
     }
 
     FireRenderCallback();
   }
 }
 
 void AudioDevice::FireRenderCallback() {
   if (callback_) {
     // Update the audio-delay measurement then ask client to render audio.
     callback_->Render(audio_data_, buffer_size_, audio_delay_milliseconds_);
 
     // Interleave, scale, and clip to int16.
     int16* output_buffer16 = static_cast<int16*>(shared_memory_data());
     media::InterleaveFloatToInt16(audio_data_, output_buffer16, buffer_size_);
   }
 }