Introduce AudioOutputResampler for browser side resampling.

media/audio/audio_manager_base.cc

Index: media/audio/audio_manager_base.cc
diff --git a/media/audio/audio_manager_base.cc b/media/audio/audio_manager_base.cc
index 7e5cc43afc7d9b1f152d9ac54d8fdcdde82c86ec..a45a653d7c0883cacc0689f43e5fff13a047af29 100644
--- a/media/audio/audio_manager_base.cc
+++ b/media/audio/audio_manager_base.cc
@@ -10,6 +10,8 @@
 #include "base/threading/thread.h"
 #include "media/audio/audio_output_dispatcher_impl.h"
 #include "media/audio/audio_output_proxy.h"
+#include "media/audio/audio_output_resampler.h"
+#include "media/audio/audio_util.h"
 #include "media/audio/fake_audio_input_stream.h"
 #include "media/audio/fake_audio_output_stream.h"
 #include "media/base/media_switches.h"
@@ -152,14 +154,20 @@ AudioOutputStream* AudioManagerBase::MakeAudioOutputStreamProxy(
   if (!dispatcher) {
     base::TimeDelta close_delay =
         base::TimeDelta::FromSeconds(kStreamCloseDelaySeconds);
+    const CommandLine* cmd_line = CommandLine::ForCurrentProcess();
+    if (cmd_line->HasSwitch(switches::kEnableAudioOutputResampler)) {
+      dispatcher = new AudioOutputResampler(
+          this, params,
+          GetPreferredLowLatencyOutputStreamParameters(params.channel_layout()),
+          close_delay);

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

I think we can clean up the confusing #if code if we returned the new
AOP(dispatcher) here + deleted the else branch

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

Done.

+    } else
+#if defined(ENABLE_AUDIO_MIXER)
     // TODO(dalecurtis): Browser side mixing has a couple issues that must be
     // fixed before it can be turned on by default: http://crbug.com/138098 and
     // http://crbug.com/140247
-#if defined(ENABLE_AUDIO_MIXER)
-    const CommandLine* cmd_line = CommandLine::ForCurrentProcess();
-    if (cmd_line->HasSwitch(switches::kEnableAudioMixer))
+           if (cmd_line->HasSwitch(switches::kEnableAudioMixer)) {
       dispatcher = new AudioOutputMixer(this, params, close_delay);
-    else
+    } else
 #endif
       dispatcher = new AudioOutputDispatcherImpl(this, params, close_delay);
   }
@@ -259,4 +267,13 @@ void AudioManagerBase::ShutdownOnAudioThread() {
 #endif  // defined(OS_IOS)
 }
 
+AudioParameters AudioManagerBase::GetPreferredLowLatencyOutputStreamParameters(
+    ChannelLayout channel_layout) {
+  // TODO(dalecurtis): This should include bits per channel and channel layout
+  // eventually.
+  return AudioParameters(
+      AudioParameters::AUDIO_PCM_LOW_LATENCY, channel_layout,
+      GetAudioHardwareSampleRate(), 16, GetAudioHardwareBufferSize());
+}
+
 }  // namespace media