I upgraded from KDE 4.5 to 4.6.4 (on Gentoo Linux) and am dealing with phonon for the first time. My alsa configuration is fine, and all sound players work from the command line before KDE starts. Once KDE starts, I get nothing from any app except KDE itself. In the phonon configuration, the correct devices are shown and test fine. KDE notification sounds work fine. Sounds will also play with Dragon Player, but not vlc, mplayer, alsaplayer, audacious, etc.

Here's what I get playing an mp3 with mplayer:

[AO_ALSA] Playback open error: Device or resource busy
[AO SDL] Samplerate: 44100Hz Channels: Stereo Format s16le
[AO SDL] Unable to open audio: No available audio device
DVB card number must be between 1 and 4
AO: [null] 44100Hz 2ch s16le (2 bytes per sample)
Video: no video
Starting playback...

I've seen quite a few questions like this posted around, but no good solutions.

I ran lsof on /dev/snd/pcmC0D0p and saw that knotify was using the sound device. As soon as I select "no audio output" under Manage Notifications, I get my alsa device back. I have never had to disable KDE's sound notification to use other apps before. What's the problem now with notifications that it ties up and won't release the sound device?

Please ensure that DMix is enabled on your system, and that Pulseaudio is not in use. Given that knotify4 was using the audio device directly, Pulseaudio is not a likely candidate in this case.

Either the Phonon backend you are using, or your system itself has a defective configuration or installation.

Thanks for the reply. Yes, the dmix plugin is enabled (although alsa is using the analogue device, so I'm not sure that matters) and there's no trace of pulseaudio anywhere.

john@acai ~ $ less /etc/asound.conf
pcm.!default {
type hw
card 0
}
pcm.dmixer {
type dmix
ipc_key 1024
slave {
pcm "hw:1,0"
period_time 0
period_size 1024
buffer_size 4096
rate 44100
}
bindings {
0 0
1 1
}
}
ctl.!default {
type hw
card 0

}

john@acai ~ $ lsof /dev/snd/pcm*
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
knotify4 3614 john mem CHR 116,16 720 /dev/snd/pcmC0D0p
knotify4 3614 john 19u CHR 116,16 0t0 720 /dev/snd/pcmC0D0p

Any other output or config files that would be useful to post?

Unfortunately i'm not aware of any.... Which Phonon backend is in use? That can be viewed from System Settings > Multimedia > Phonon.

I've tried with gstreamer, vlc, and xine. Makes no difference.

Ok, do other applications such as MPlayer and the like also lock the audio device? Trying with Xine/VLC/GStreamer enabled applications would probably be best for this...

No, all other apps use and release the device as they should.

I use Gentoo. I do need the phonon and phonon-kde packages, and NOT the qt-phonon package, right? (The latter is blocked, apparently by design.)

The "phonon" and "phonon-kde" packages are the correct ones as far as I can tell. "phonon-qt" is definitely the wrong one.