Sound shuts off when VM out of focus

[AlanK]

When playing a video or something in the VM, then click on a window outside the VM, sound shuts off in the VM. Sometimes clicking on the VM will restore the sound but sometimes not.

[pgeek]

This behaviour also occurs for Linux guests running under a Windows 7 host with 3.1.2.

Only some focus changes halt the VM sound, though: games, foobar2000,  Steam. As soon as the offending application is shut, the VM sound returns without further action needed.

[pgeek]

Some of these issues could probably be solved by changing the flags used to create the sound buffer in the DirectSound audio driver code.

Adding the DSBCAPS_GLOBALFOCUS flag should be enough:

--- src/VBox/Devices/Audio/dsoundaudio.c.orig	2009-12-17 14:27:41.000000000 +0000
+++ src/VBox/Devices/Audio/dsoundaudio.c	2009-12-24 13:07:20.431769153 +0000
@@ -568,7 +568,7 @@
 
     memset (&dsbd, 0, sizeof (dsbd));
     dsbd.dwSize = sizeof (dsbd);
-    dsbd.dwFlags = DSBCAPS_PRIMARYBUFFER;
+    dsbd.dwFlags = DSBCAPS_PRIMARYBUFFER | DSBCAPS_GLOBALFOCUS;
     dsbd.dwBufferBytes = 0;
     dsbd.lpwfxFormat = NULL;
 

[frank]

The question is if this behavior is a bug or a feature ... Surely this isn't critical.

[michaln]

This is not so much a bug as the default DirectSound behavior. It is not true that switching focus to another window automatically stops the VM sound. It is true that switching to another application which uses DirectSound will stop the VM sound; that is because VirtualBox currently uses the DSBCAPS_STICKYFOCUS setting for its sound buffer. For example on my system, switching focus to a command prompt or to Acrobat Reader does not stop the VM from playing, but switching to Firefox does.

Giving focus to the VM again does restore the audio, unless of course there is another application using the write-primary DirectSound cooperative level.

[pgeek]

As for being either a feature or bug, the fact that the issue has been reported could be an indication of a reasonable expectation - from some users at least - that if you are using the VM to play sound it should not depend on it having focus or on the applications running on the host. Hence the suggestion to depart from the default DirectSound behaviour.

[frank]

Sure but the experience shows that changing such behavior is appreciated by some users and heavily disliked by others. Though we will change this behavior in the next major release as this is the standard behavior on other hosts (Linux, Mac OS X) as well.

[pgeek]

Agreed. You can also try to please everyone by making it configurable, although at a much higher development cost. Glad to know about the planned behaviour change anyway.