Issue with selected mixer channel

Submitted by DoctorPepper on Sun, 2011-02-20 13:16

Forums:

I recently moved back to Slackware 13.1 from Xubuntu 10.10. I had been using the Ubuntu-supplied version of MOC with no issues at all. MOC does not come in the default Slackware install, so I used the slackbuild script from www.slackbuilds.org, which is 2.5.0 Alpha 4. The issue I am seeing is my system volume control works against the "master" mixer channel, and MOC uses the PCM mixer channel. I have tried to change the mixer settings in the .moc/config file, but when I change the ALSA mixer setting to make MOC use the master channel, MOC displays "Master 00%", and the volume can't be changed.

This issue isn't crippling, MOC still works, I just have to remember to turn the PCM mixer channel back to 100% when I'm finished using MOC.

Btw, I'm using the example config file that was included with the source package.

Did I miss anything? Is there some way for me to make MOC use the master mixer channel, like the rest of my system?

TIA

Ted Phelps

Thu, 2011-05-05 02:03

I was having the same issue. Today I spent some time with a debugger and I think I've tracked down the problem. The ALSA documentation is unclear, but I that the channel_id passed to snd_mixer_selem_has_playback_channel and snd_mixer_selem_get_playback_volume is incorrectly transformed into a bitmask in alsa_read_mixer_raw. Replacing 1 << i with just i at alsa.c:207 and alsa.c:212 seems to make it work correctly for me.

I've tried including a patch here, but I haven't figured out how to prevent the forum software from mangling it. Sorry about that.

-Ted

jcf

Thu, 2011-05-05 08:07

And if 'DoctorPepper' can confirm it works on his system
then I'll commit it. Good work, Ted.

jcf

Sun, 2011-05-22 23:24

I have not had independant verification that Ted's fix actually
resolves the problem, but I have checked against other ALSA-using
packages and it seems consistant with those.

Committed to SVN as r2318.