On Tue, 19 Dec 2006, Benjamin Eikel wrote:

> Hello,
> I am trying to setup a lowpass filter for my subwoofer channel. I used 
> the configuration template which is given in the ALSA wiki 
> (http://alsa.opensrc.org/SurroundSound) as a template.
> My asound.conf works when I use it like it is given below (sound from 
> all speakers). But when I uncomment the second LADSPA plugin for the 
> lowpass (plugin number 1), then I will only hear sound from the 
> subwoofer (so only channel number 2 is processed lowpass_21to21). The 
> other channels seem to be muted. I also tried the same setup which is 
> given in the Wiki mentioned above, but this does not work at all (the 
> delay_0.01s plugin is called delay_0,01s on my machine; it think it's 
> because of the German locale; that's why I am using the ids for the 
> LADSPA plugins now). I tried to set the policy of my first LADSPA plugin 
> (number 0) to 'none', but this did not help. I was still hearing only 
> the sound from the subwoofer. I tried to use 3 plugins for the 3 
> channels, each with policy none, but this did not work too. The ALSA 
> documentation I found (e.g. 
> http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html) is not 
> very helpful at all (I am not sure how to set these bindings inside the 
> plugins correctly). When I connect upmix_20to51 directly to 
> upmix_21to51, the sound is working fine (of course without lowpass).
> I would greatly appreciate any hint about what I am doing wrong.

It was a bug (thanks for this report). The patch (or full file) which 
corrects "policy none" behaviour is here:


Or, please, wait for the alsa-lib 1.0.14rc2 package which will contain 
this change.


Jaroslav Kysela <[EMAIL PROTECTED]>
Linux Kernel Sound Maintainer
ALSA Project, SUSE Labs

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