Change the way we are sending audio data to driver when using WaveOut API.

Before, we were "feeding" the driver in the callback when OS returned audio
buffer to us. MSDN disallows that, but We were avoiding deadlock when stopping
the stream by using some clever tricks. Unfortunately, exactly the same
deadlock happens when Windows were draining audio stream when switching
the device, and our tricks did not help, as we were not controlling exact timing.

Fix is to separate receiving freed buffer and "feeding" audio driver. Now we are
using CALLBACK_EVENT wave out mode in which Windows signal event when buffer runs
out of data, and using RegisterWaitForSingleObject() so our callback is called by
one of thread pool threads.

Stopping of playback became slower because now it is synchronous. If that ever
become a problem we can use singleton that keeps track of the playing audio
streams, than stopping can become instaneous, at a cost of more complex checks
in the callback.

Unfortunately, no automatic test, as there is no documented way to programmatically
switch default audio device on Windows. People were able to figure it out (see
http://www.daveamenta.com/2011-05/programmatically-or-command-line-change-the-default-sound-playback-device-in-windows-7/),
but there is no guarantee it will continue to work in Win8, or even in next Service Pack
for Win7.

BUG=41036

TEST=Play any HTML5 audio/video on Windows and change default audio device
TEST=using "Control Panel | Sound". There should be no hang, you should hear
TEST=audio from the newly chosen device.

Review URL: http://codereview.chromium.org/8591028

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@112147 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 5 insertions, 0 deletions

diff --git a/media/audio/audio_util.cc b/media/audio/audio_util.cc
index 4aec30d..48be2db 100644
--- a/media/audio/audio_util.cc
+++ b/media/audio/audio_util.cc
@@ -293,6 +293,11 @@ size_t GetAudioHardwareBufferSize() {
 #if defined(OS_MACOSX)
   return 128;
 #elif defined(OS_WIN)
+  if (base::win::GetVersion() <= base::win::VERSION_XP) {
+    // Fall back to Windows Wave implementation on Windows XP or lower
+    // and assume 48kHz as default sample rate.
+    return 2048;
+  }
   // 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 =