I'm using udev, and have set up alsa sound on my machine. I kept getting an error when entering KDE that /dev/dsp can't be opened. I checked the audio group and confirmed that I was added there.
I check the /dev files and find that /dev/dsp is assigned to the root group. I changed that to audio. It didn't work, but I figured I'd reboot to get everything reset (I come from the windows world), and it still didn't work. I went back to the /dev files to check things out, and /dev/dsp is again assigned to the root group. What's going on?
/dev/dsp is a link created by udev. The fact that it's in the root group shouldn't affect you. You should check the permission of /dev/sound/dsp instead. On my system, I have:
lrwxrwxrwx 1 root root 9 Sep 12 00:44 /dev/dsp -> sound/dsp
crw-rw---- 1 root audio 14, 3 Sep 12 00:44 /dev/sound/dsp
BTW, I am not using KDE.
Make sure you are in group "audio".
Make sure that in Control Center > Sound & Multimedia > Sound System > Hardware you have "Advanced Linux Sound Architecture" selected from the drop-down list - I think this will make arts (the sound backend some kde apps use) use ALSA as output audio device. ALSA has software mixing enabled by default starting 1.0.9, so this way you'd be able to have sound playing from multiple sources for all ALSA-aware apps.
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Thanks; I went back and checked the dev files as indicated and now see how that all works, audio group had permissions.
I was already a part of audio group, but checked it again - and I wasn't any more; not sure of how that happened but I put myself back in it, and now sound works.
I had already gone into the Control Panel and set it up for ALSA, although that was just a guess so I'm glad to know I guessed right.
Now for mplayer and xvid........
You should disable sound in the control center....
that applies to arts only, you will get better results and true multi-app sound by unchecking the sound option and just letting alsa do its own thing