Adding experimental exclusive-mode streaming to WASAPIAudioOutputStream

media/audio/audio_util.cc

Index: media/audio/audio_util.cc
diff --git a/media/audio/audio_util.cc b/media/audio/audio_util.cc
index 4035d28a589fa4737cee6b1b5561fcca3a02f443..a32167e1dd8f35b7e003e21c918da22215641028 100644
--- a/media/audio/audio_util.cc
+++ b/media/audio/audio_util.cc
@@ -20,20 +20,20 @@
 #include "base/logging.h"
 #include "base/shared_memory.h"
 #include "base/time.h"
-#if defined(OS_WIN)
-#include "base/sys_info.h"
-#include "base/win/windows_version.h"
-#include "media/audio/audio_manager_base.h"
-#endif
 #include "media/audio/audio_parameters.h"
 #include "media/audio/audio_util.h"
+
 #if defined(OS_MACOSX)
 #include "media/audio/mac/audio_low_latency_input_mac.h"
 #include "media/audio/mac/audio_low_latency_output_mac.h"
-#endif
-#if defined(OS_WIN)
+#elif defined(OS_WIN)
+#include "base/command_line.h"
+#include "base/sys_info.h"
+#include "base/win/windows_version.h"
 #include "media/audio/win/audio_low_latency_input_win.h"
 #include "media/audio/win/audio_low_latency_output_win.h"
+#include "media/base/media_switches.h"
+#include "media/audio/audio_manager_base.h"
 #endif
 
 using base::subtle::Atomic32;
@@ -351,10 +351,15 @@ int GetAudioHardwareSampleRate() {
     return 48000;
   }
 
-  // Hardware sample-rate on Windows can be configured, so we must query.
-  // TODO(henrika): improve possibility to specify audio endpoint.
-  // Use the default device (same as for Wave) for now to be compatible.
-  return WASAPIAudioOutputStream::HardwareSampleRate(eConsole);
+  const CommandLine* cmd_line = CommandLine::ForCurrentProcess();
+  if (!cmd_line->HasSwitch(switches::kEnableExclusiveMode)) {

[scherkus (not reviewing), 2012/06/28 00:04:41]

doh rietveld swallowed my comment from the last PS :(

I was going to say it smells a bit funny that we have a few bits + pieces of
switch-checking code here. Ideally we isolate all changes that require this flag
in one spot and be done with it. In particular, this code is relying on
AudioManagerWin to be doing its job creating exclusive WASAPIAOS objects.

I don't think there's much we can fix in the short term. Longer term I think
what we actually want is to most of this file moved into the OS-specific
AudioManager implementations. That way we could create an AudioManagerWin impl
that knows it's working in exclusive mode and as such isolate all the
exclusive-mode code but alas we'll have to save that for another time :)

[henrika (OOO until Aug 14), 2012/07/25 11:18:22]

Point taken. Will improve in an upcoming version.

+    // Hardware sample-rate on Windows can be configured, so we must query.
+    // TODO(henrika): improve possibility to specify audio endpoint.
+    // Use the default device (same as for Wave) for now to be compatible.
+    return WASAPIAudioOutputStream::HardwareSampleRate(eConsole);

[scherkus (not reviewing), 2012/06/28 00:04:41]

I also noticed that all current usage for E_ROLE is eConsole. Do we have plans
to remove this argument at some point and perhaps make it a constant inside the
WASAPI .cc?

[henrika (OOO until Aug 14), 2012/07/25 11:18:22]

It is not so simple to fix. We have a better solution today on the input side
where I have added support for proper device selection. This parameter is then
replaced by a const std::string& device_id. There has so far not been any
requests for selection of (other than default device) on the output side. Hmmm,
given this fact, it might in fact be better to hide eConsole as you propose.
Improving the TODO comment.

+  } else {
+    return 44100;

[scherkus (not reviewing), 2012/06/28 00:04:41]

where is 44100 coming from?

for example we seem to use 48000 on other branches -- some docs would be nice

[henrika (OOO until Aug 14), 2012/07/25 11:18:22]

Rewrote this section and added new comments to make it more clear.

+  }
 #elif defined(OS_ANDROID)
   return 16000;
 #else
@@ -397,6 +402,15 @@ size_t GetAudioHardwareBufferSize() {
     // and assume 48kHz as default sample rate.
     return 2048;
   }
+
+  // TODO(croger): tune this size to best possible WebAudio performance.

[scherkus (not reviewing), 2012/06/28 00:04:41]

s/croger/crogers

[henrika (OOO until Aug 14), 2012/07/25 11:18:22]

Done.

+  // WebRTC always uses 480 for Windows and does not call this method.
+  // Note that exclusive mode is experimental.
+  const CommandLine* cmd_line = CommandLine::ForCurrentProcess();
+  if (cmd_line->HasSwitch(switches::kEnableExclusiveMode)) {
+    return 256;
+  }
+
   // This call must be done on a COM thread configured as MTA.
   // TODO(tommi): http://code.google.com/p/chromium/issues/detail?id=103835.
   int mixing_sample_rate =