Work on improving PpbAudioConfig:RecommendSampleFrameCount

content/renderer/pepper_plugin_delegate_impl.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 "content/renderer/pepper_plugin_delegate_impl.h"
 
 #include <cmath>
 #include <map>
 #include <queue>
 
@@ skipping 16 matching lines @@
 #include "content/common/media/audio_messages.h"
 #include "content/common/pepper_file_messages.h"
 #include "content/common/pepper_plugin_registry.h"
 #include "content/common/pepper_messages.h"
 #include "content/common/quota_dispatcher.h"
 #include "content/common/view_messages.h"
 #include "content/public/common/content_switches.h"
 #include "content/public/common/context_menu_params.h"
 #include "content/public/renderer/content_renderer_client.h"
 #include "content/renderer/gamepad_shared_memory_reader.h"
+#include "content/renderer/media/audio_hardware.h"
 #include "content/renderer/media/audio_input_message_filter.h"
 #include "content/renderer/media/audio_message_filter.h"
 #include "content/renderer/media/media_stream_dispatcher.h"
 #include "content/renderer/media/media_stream_dispatcher_eventhandler.h"
 #include "content/renderer/media/pepper_platform_video_decoder_impl.h"
 #include "content/renderer/p2p/p2p_transport_impl.h"
 #include "content/renderer/pepper_platform_context_3d_impl.h"
 #include "content/renderer/pepper_platform_video_capture_impl.h"
 #include "content/renderer/render_thread_impl.h"
 #include "content/renderer/render_view_impl.h"
@@ skipping 168 matching lines @@
   int32 stream_id_;
 
   base::MessageLoopProxy* main_message_loop_proxy_;
 
   DISALLOW_COPY_AND_ASSIGN(PlatformAudioImpl);
 };
 
 bool PlatformAudioImpl::Initialize(
     uint32_t sample_rate, uint32_t sample_count,
     webkit::ppapi::PluginDelegate::PlatformAudioCommonClient* client) {
-
   DCHECK(client);
   // Make sure we don't call init more than once.
   DCHECK_EQ(0, stream_id_);
 
   client_ = client;
 
   AudioParameters params;
-  params.format = AudioParameters::AUDIO_PCM_LINEAR;
+  const uint32_t kMaxSampleCountForLowLatency = 2048;
+  // Use the low latency back end if the client request is compatible, and
+  // the sample count is low enough to justify using AUDIO_PCM_LOW_LATENCY.
+  if (sample_rate == audio_hardware::GetOutputSampleRate() &&
+      sample_count <= kMaxSampleCountForLowLatency &&
+      sample_count % audio_hardware::GetOutputBufferSize() == 0)
+    params.format = AudioParameters::AUDIO_PCM_LOW_LATENCY;
+  else
+    params.format = AudioParameters::AUDIO_PCM_LINEAR;
   params.channels = 2;
   params.sample_rate = sample_rate;
   params.bits_per_sample = 16;
   params.samples_per_packet = sample_count;
 
   ChildProcess::current()->io_message_loop()->PostTask(
       FROM_HERE,
       base::Bind(&PlatformAudioImpl::InitializeOnIOThread, this, params));
   return true;
 }
@@ skipping 1107 matching lines @@
                                                           bool final_result) {
   render_view_->reportFindInPageMatchCount(identifier, total, final_result);
 }
 
 void PepperPluginDelegateImpl::SelectedFindResultChanged(int identifier,
                                                          int index) {
   render_view_->reportFindInPageSelection(
       identifier, index + 1, WebKit::WebRect());
 }
 
+uint32_t PepperPluginDelegateImpl::GetAudioHardwareOutputSampleRate() {
+  return static_cast<uint32_t>(audio_hardware::GetOutputSampleRate());
+}
+
+uint32_t PepperPluginDelegateImpl::GetAudioHardwareOutputBufferSize() {
+  return static_cast<uint32_t>(audio_hardware::GetOutputBufferSize());
+}
+
 webkit::ppapi::PluginDelegate::PlatformAudio*
 PepperPluginDelegateImpl::CreateAudio(
     uint32_t sample_rate,
     uint32_t sample_count,
     webkit::ppapi::PluginDelegate::PlatformAudioCommonClient* client) {
   scoped_refptr<PlatformAudioImpl> audio(new PlatformAudioImpl());
   if (audio->Initialize(sample_rate, sample_count, client)) {
     // Balanced by Release invoked in PlatformAudioImpl::ShutDownOnIOThread().
     return audio.release();
   } else {
@@ skipping 861 matching lines @@
 void PepperPluginDelegateImpl::UnSetAndDeleteLockTargetAdapter(
     webkit::ppapi::PluginInstance* instance) {
   LockTargetMap::iterator it = mouse_lock_instances_.find(instance);
   if (it != mouse_lock_instances_.end()) {
     MouseLockDispatcher::LockTarget* target = it->second;
     render_view_->mouse_lock_dispatcher()->OnLockTargetDestroyed(target);
     delete target;
     mouse_lock_instances_.erase(it);
   }
 }