[pulseaudio-discuss] cmipci, pulseaudio and 5.1 — unable to contol center/LFE

Erik Boritsch borych at gmx.de
Wed Aug 18 01:25:25 PDT 2010


I have a CM8738-MC6 soundcard with 5.1 analog surround. With pulseaudios
5.1 profile I am unable to control center and LFE channels. Changing the
values for these channels achieves nothing. This is partly due to the
way the soundcard works in alsa. Quoting ALSA Wiki from

"CM8x38 chip can use ADC as the second DAC so that two different stereo
channels can be used for front/rear playbacks. Since there are two DACs,
both streams are handled independently unlike the 4/6ch multi-channel
playbacks in the section below.
As default, ALSA driver assigns the first PCM device (i.e. hw:0,0 for
card#0) for front and 4/6ch playbacks, while the second PCM device
(hw:0,1) is assigned to the second DAC for rear playback."

In my case, it seems that center/LFE are on hw:1,1 (with other channels
being on hw:1,0). I have tried adding followings to .asoundrc:

pcm.softvol {
    type softvol
    slave {
        pcm "hw:1,1"
    control {
        name "SoftMaster"

pcm.dsp1 {
    type plug
    slave.pcm "softvol"
    slave.channels 6
    route_policy duplicate

pcm.!default {
    type plug
    slave.pcm "softvol"
    slave.channels 6
    route_policy duplicate

With this config I can control volume for all the channels
simultaneously in alsa using the "Softmaster" control. 
However, I am lost about how can I make this work in pulseaudio. 
I can edit analog-output.conf.common to make pulseaudio control
"SoftMaster", but this control doesn't affect sounds routed through

Can anybody give me an advice of how to configure my sound setup so I
can change volume for all the channels simultaneously in pulseaudio?

Erik Boritsch

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