Introduce AudioOutputResampler for browser side resampling.

content/renderer/pepper/pepper_platform_audio_output_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/pepper_platform_audio_output_impl.h"
 
 #include "base/bind.h"
+#include "base/command_line.h"
 #include "base/logging.h"
 #include "base/message_loop_proxy.h"
 #include "build/build_config.h"
 #include "content/common/child_process.h"
 #include "content/common/media/audio_messages.h"
 #include "content/renderer/media/audio_hardware.h"
 #include "content/renderer/media/audio_message_filter.h"
 #include "content/renderer/render_thread_impl.h"
+#include "media/base/media_switches.h"
 
 namespace content {
 
 // static
 PepperPlatformAudioOutputImpl* PepperPlatformAudioOutputImpl::Create(
     int sample_rate,
     int frames_per_buffer,
     webkit::ppapi::PluginDelegate::PlatformAudioOutputClient* client) {
   scoped_refptr<PepperPlatformAudioOutputImpl> audio_output(
       new PepperPlatformAudioOutputImpl());
@@ skipping 87 matching lines @@
     int sample_rate,
     int frames_per_buffer,
     webkit::ppapi::PluginDelegate::PlatformAudioOutputClient* client) {
   DCHECK(client);
   // Make sure we don't call init more than once.
   DCHECK_EQ(0, stream_id_);
 
   client_ = client;
 
   media::AudioParameters::Format format;
-  const int kMaxFramesForLowLatency = 2047;
-  // 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() &&
-      frames_per_buffer <= kMaxFramesForLowLatency &&
-      frames_per_buffer % audio_hardware::GetOutputBufferSize() == 0) {
+
+  // TODO(dalecurtis): Limit to windows and 2ch linux/mac only since neither of

[scherkus (not reviewing), 2012/09/10 12:47:47]

nit: proper capitalization on Windows/Linux/Mac

also this comment is a bit confusing -- are you saying that Windows supports
multichannel but Linux/Mac only support 2 channels? What about mono?

[DaleCurtis, 2012/09/10 14:05:51]

Removed comment. After thinking about it, I intend to land the resilience patch
before removing this from behind a flag. Which means we'll just fail and reopen
the device in non-low latency mode.

+  // those support multichannel currently.
+  const CommandLine* cmd_line = CommandLine::ForCurrentProcess();
+  if (cmd_line->HasSwitch(switches::kEnableAudioOutputResampler)) {
     format = media::AudioParameters::AUDIO_PCM_LOW_LATENCY;

[henrika (OOO until Aug 14), 2012/09/10 12:41:17]

Some comments here perhaps.

[DaleCurtis, 2012/09/10 14:05:51]

Done.

   } else {
-    format = media::AudioParameters::AUDIO_PCM_LINEAR;
+    const int kMaxFramesForLowLatency = 2047;
+    // 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() &&
+        frames_per_buffer <= kMaxFramesForLowLatency &&
+        frames_per_buffer % audio_hardware::GetOutputBufferSize() == 0) {
+      format = media::AudioParameters::AUDIO_PCM_LOW_LATENCY;
+    } else {
+      format = media::AudioParameters::AUDIO_PCM_LINEAR;
+    }
   }
 
   media::AudioParameters params(format, CHANNEL_LAYOUT_STEREO, sample_rate, 16,
                                 frames_per_buffer);
 
   ChildProcess::current()->io_message_loop()->PostTask(
       FROM_HERE,
       base::Bind(&PepperPlatformAudioOutputImpl::InitializeOnIOThread,
                  this, params));
   return true;
@@ skipping 22 matching lines @@
 
   ipc_->CloseStream(stream_id_);
   ipc_->RemoveDelegate(stream_id_);
   stream_id_ = 0;
 
   Release();  // Release for the delegate, balances out the reference taken in
               // PepperPluginDelegateImpl::CreateAudio.
 }
 
 }  // namespace content