Introduce AudioOutputResampler for browser side resampling.

content/renderer/pepper/pepper_platform_audio_output_impl.cc

Index: content/renderer/pepper/pepper_platform_audio_output_impl.cc
diff --git a/content/renderer/pepper/pepper_platform_audio_output_impl.cc b/content/renderer/pepper/pepper_platform_audio_output_impl.cc
index 03f271e22b151adf1122d91bb9eacc0f75ea5a3d..de4d62b94d4c8b56f716076ebf992e4e42aae8ac 100644
--- a/content/renderer/pepper/pepper_platform_audio_output_impl.cc
+++ b/content/renderer/pepper/pepper_platform_audio_output_impl.cc
@@ -5,6 +5,7 @@
 #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"
@@ -13,6 +14,7 @@
 #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 {
 
@@ -120,15 +122,23 @@ bool PepperPlatformAudioOutputImpl::Initialize(
   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) {
+
+  const CommandLine* cmd_line = CommandLine::ForCurrentProcess();
+  if (cmd_line->HasSwitch(switches::kEnableAudioOutputResampler)) {

[scherkus (not reviewing), 2012/09/10 14:34:11]

Doesn't this switch need to be passed via
content/browser/renderer_host/render_process_host_impl.cc to make it to the
renderer process?

[DaleCurtis, 2012/09/10 14:53:51]

Oh yeah. This was working previously because I didn't have the LOW_LATENCY
restriction in AudioManagerBase.

+    // Rely on AudioOutputResampler to handle any inconsistenties between the

[scherkus (not reviewing), 2012/09/10 14:25:32]

sp: inconsistenties -> inconsistencies

[DaleCurtis, 2012/09/10 14:53:51]

Done.

+    // hardware params required for low latency and the requested params.
     format = media::AudioParameters::AUDIO_PCM_LOW_LATENCY;
   } 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) {

[scherkus (not reviewing), 2012/09/10 14:34:11]

can we de-nest this set of branches into the following:

if (HasSwitch) {
  format = LOW_LATENCY;
} else if (low latency stuff checks out) {
  format = LOW_LATENCY;
} else {
  format = LINEAR;
}

have the else + another set of if/else is confusing

alternatively you can tack the HasSwitch() as an ||

[DaleCurtis, 2012/09/10 14:53:51]

Done.

+      format = media::AudioParameters::AUDIO_PCM_LOW_LATENCY;
+    } else {
+      format = media::AudioParameters::AUDIO_PCM_LINEAR;
+    }
   }
 
   media::AudioParameters params(format, CHANNEL_LAYOUT_STEREO, sample_rate, 16,