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 ] ]
}
> 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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