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$ uname -a
Linux nbb 3.2.1-2-ARCH #1 SMP PREEMPT Mon Jan 23 12:40:01 UTC 2012 x86_64 Intel(R) Xeon(R) CPU W3520 @ 2.67GHz GenuineIntel GNU/Linux

I have an Intel ADA198x HD Audio interface (I believe this is a relatively standard onboard audio controller) with digital optical out via SPDIF. The digital out feeds into a receiver, which acts as a DAC for my headphones and speakers.

I'm using alsa, and as I'm using KDE then Phonon is running with a gstreamer backend.

After first booting, if I go to systemsettings and click Multimedia, then go to the Phonon tab and click "Test" then I usually get sound out of the digital port. But then I went to go play some music, and nothing came out. I messed around with a few other things (VLC is set to use digital audio), then I went back to systemsettings. Now it tells me the SPDIF interface is disabled, and when I press the "Test" button it falls back to analog and sound comes out of the analog speakers (but not the digital port).

UPDATE: I suspect something is grabbing the audio device and not releasing it. On startup, I can play music using VLC. But then when I start Firefox and try to play music from a cloud player, I get no sound, I can't play music anywhere, and the above problems occur.

How can I get this working?

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up vote 1 down vote accepted

I'm running a virtual machine inside Oracle VirtualBox. Apparently VirtualBox was grabbing the audio driver when a sound was played and then not releasing it afterward.

I discovered this by forcibly restarting alsa, which kills everything holding the sound device, and seeing my VM get terminated.

The solution was to disable audio for that VM.

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