Clemens,
thank you for your reply - it has been the only helpful one so far.
Am 24.08.2015 um 08:43 schrieb Clemens Ladisch:
> Gunnar Arndt wrote:
>> the configuration of an Alsa PCM device which does that job
>> automatically in real time:
>>
>> (1) Grab a stereo signal from the line input.
>> (2) Invert either the left OR the right channel (i.e. multiply its
>> signal's amplitude by minus 1).
>> (3) Merge the channels to mono.
> pcm.fake_balanced {
> type route
> slave.pcm "hw:0" # or whatever
> ttable [ [ 1 -1 ] ]
> }
I had to add some stuff, but now it works. My asound.conf looks like
this now:
pcm.symmetric {
type route
slave {
pcm "hw:0,2"
channels 2
}
ttable [ [ 1 -1 ] [ 1 -1 ] ]
}
ctl.symmetric {
type hw
card 0
}
I had tested a similar solution yesterday evening after I had found that
negative scaling is possible here:
http://www.volkerschatz.com/noise/alsa.html
but the nested array notation you have suggested makes things easier.
Regards
Gunnar
>
>> http://alsa.opensrc.org/Asoundrc#Downmix_stereo_to_mono
>> But that suggestion does not seem work as expected - if I use that
>> configuration, the left channel is doubled, and the right channel is
>> dropped when recording (or the other way, doesn't matter).
> The ttable specifies how the channels of the route device are mapped
> from/to the channels of the slave device. It's a two-dimensional array
> (i.e., an array containing arrays), with the outer array having one
> entry for each route-device channel, and each inner array having one
> entry for each slave channel. (The "ttable.r.s value" mechanism of
> specifying table entries works too, but is typcially not as easy to
> understand.)
>
>
> Regards,
> Clemens
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