Resolves "Huge increase in audio latency on Windows following r192046"

media/audio/win/audio_manager_win.cc

Index: media/audio/win/audio_manager_win.cc
diff --git a/media/audio/win/audio_manager_win.cc b/media/audio/win/audio_manager_win.cc
index 4ada0a17778365676607dbcb3acd84df43a87f03..880fac35e012fb5109b8abd64371e959249a3952 100644
--- a/media/audio/win/audio_manager_win.cc
+++ b/media/audio/win/audio_manager_win.cc
@@ -390,14 +390,21 @@ AudioParameters AudioManagerWin::GetPreferredOutputStreamParameters(
   }
 
   if (input_params.IsValid()) {
-    if (CoreAudioUtil::IsSupported() &&
-        CoreAudioUtil::IsChannelLayoutSupported(eRender, eConsole,
-            input_params.channel_layout())) {
-      // Open up using the same channel layout as the source if it is
-      // supported by the hardware.
-      channel_layout = input_params.channel_layout();
-      VLOG(1) << "Hardware channel layout is not used; using same "
-              << "layout as the source instead (" << channel_layout << ")";
+    if (CoreAudioUtil::IsSupported()) {
+        // Check if it is possible to open up at the specified input channel

[DaleCurtis, 2013/04/15 18:08:57]

Indent is wrong; should be 2 spaces.

[henrika (OOO until Aug 14), 2013/04/15 20:28:28]

Will fix.

[henrika (OOO until Aug 14), 2013/04/16 09:04:35]

Done.

+        // layout but avoid checking if the specified layout is the same as the
+        // hardware (preferred) layout. We do this extra check to avoid the
+        // CoreAudioUtil::IsChannelLayoutSupported() overhead in most cases.
+        if (input_params.channel_layout() != channel_layout) {

[DaleCurtis, 2013/04/15 18:08:57]

In the Exclusive mode case, channel_layout won't be set yet, so you'll end up
making an extra check here.

[henrika (OOO until Aug 14), 2013/04/15 20:28:28]

Can you elaborate. Do you want me to add a flag-check and do what if the flag is
enabled? I assume you want to always open at input layout in exclusive mode.

[DaleCurtis, 2013/04/15 20:31:07]

In the HasSwitch() block above, I'd just add a:

if (input_params.IsValid())
  channel_layout = input_params.channel_layout();

[henrika (OOO until Aug 14), 2013/04/16 09:04:35]

Done.

+          if (CoreAudioUtil::IsChannelLayoutSupported(eRender, eConsole,
+                  input_params.channel_layout())) {

[DaleCurtis, 2013/04/15 18:08:57]

Wrong indent; you can't partially wrap some of the parameters and not others. 
It's either all or nothing.

[henrika (OOO until Aug 14), 2013/04/15 20:28:28]

Will fix.

[henrika (OOO until Aug 14), 2013/04/16 09:04:35]

Done.

+            // Open up using the same channel layout as the source if it is
+            // supported by the hardware.
+            channel_layout = input_params.channel_layout();
+            VLOG(1) << "Hardware channel layout is not used; using same layout"
+                    << " as the source instead (" << channel_layout << ")";
+        }
+      }
     }
     input_channels = input_params.input_channels();
     if (use_input_params) {