Improves CoreAudioUtil::IsSupported by also loading Audioses.dll DLL

media/audio/win/core_audio_util_win.cc

Index: media/audio/win/core_audio_util_win.cc
diff --git a/media/audio/win/core_audio_util_win.cc b/media/audio/win/core_audio_util_win.cc
index b501cbfa98c6400c326ef26301419ce645eb6514..a15e5f4a094e4b9585debe6427ee95290be9d183 100644
--- a/media/audio/win/core_audio_util_win.cc
+++ b/media/audio/win/core_audio_util_win.cc
@@ -66,6 +66,18 @@ static ChannelLayout ChannelConfigToChannelLayout(ChannelConfig config) {
   }
 }
 
+bool LoadAudiosesDll() {
+  static const wchar_t* const kAudiosesDLL =
+      L"%WINDIR%\\system32\\audioses.dll";
+
+  wchar_t path[MAX_PATH] = {0};
+  ExpandEnvironmentStringsW(kAudiosesDLL, path, arraysize(path));
+  if (!LoadLibraryExW(path, NULL, LOAD_WITH_ALTERED_SEARCH_PATH))

[tommi (sloooow) - chröme, 2012/12/21 09:58:14]

return LoadLibraryExW(path, NULL, LOAD_WITH_ALTERED_SEARCH_PATH)) != NULL;

[henrika (OOO until Aug 14), 2012/12/21 10:03:36]

OK. I followed your example BTW ;-)

[tommi (sloooow) - chröme, 2012/12/21 10:29:18]

Hah, well, you should have noticed that in the other case there was a loop! :)
Think about how this would have worked:

  for (int i = 0; i < arraysize(kMfDLLs); ++i) {
    wchar_t path[MAX_PATH] = {0};
    ExpandEnvironmentStringsW(kMfDLLs[i], path, arraysize(path));
    return LoadLibraryExW(path, NULL, LOAD_WITH_ALTERED_SEARCH_PATH)) != NULL;
  }

+    return false;
+
+  return true;
+}
+
 // Scoped PROPVARIANT class for automatically freeing a COM PROPVARIANT
 // structure at the end of a scope.
 class ScopedPropertyVariant {
@@ -103,7 +115,17 @@ bool CoreAudioUtil::IsSupported() {
   // Microsoft does not plan to make the Core Audio APIs available for use
   // with earlier versions of Windows, including Microsoft Windows Server 2003,
   // Windows XP, Windows Millennium Edition, Windows 2000, and Windows 98.
-  return (base::win::GetVersion() >= base::win::VERSION_VISTA);
+  if (base::win::GetVersion() < base::win::VERSION_VISTA)
+    return false;
+
+  // The audio core APIs are implemented in the Mmdevapi.dll and Audioses.dll
+  // system components, both of which run in user mode.

[tommi (sloooow) - chröme, 2012/12/21 09:58:14]

nit: dll's generally do run in usermode so you can remove that bit :)

[henrika (OOO until Aug 14), 2012/12/21 10:03:36]

Got it. Copy paste from MSDN.

+  // Dependcy Walker shows that it is enough to verify possibility to load

[tommi (sloooow) - chröme, 2012/12/21 09:58:14]

Dependency

[henrika (OOO until Aug 14), 2012/12/21 10:03:36]

Done.

+  // the Audioses DLL since it loads Mmdevapi.dll as well.

[tommi (sloooow) - chröme, 2012/12/21 09:58:14]

s/it loads Mmdevapi.dll as well/it depends on Mmdevapi.dll.
The loader loads the dlls, they don't do it themselves.

[henrika (OOO until Aug 14), 2012/12/21 10:03:36]

Thanks. Much better.

+  // See http://crbug.com/166397 why this extra step is required to guarantee
+  // Core Audio support.
+  static bool g_audioses_dll_available = LoadAudiosesDll();
+  return g_audioses_dll_available;
 }
 
 base::TimeDelta CoreAudioUtil::RefererenceTimeToTimeDelta(REFERENCE_TIME time) {