Can I downmix stereo audio to mono?

Question

I have one speaker next to my computer which I use mostly as a headphone amplifier. On occasion I need to use it as a loudspeaker. Is it possible to quickly change the audio output from stereo to mono, either system-wide or as a plugin for a media player?

Answer 1

Find the name of your audio sink by running pacmd list-sinks | grep name:. Then run this command: pacmd load-module module-remap-sink sink_name=mono master=<name_of_audio sink_given_by_previous_command> channels=2 channel_map=mono,mono (taking care to remove the angled brackets), or add the argument to pacmd to /etc/pulse/default.pa , to have it run at startup. Then in Sound Preferences choose "Mono" as the output but remember to reduce volumes by half, since two channels are getting mixed into one, or else you'll have distortion. To test, run : speakertest -c 2 -t sine.

Answer 2

I've cast answer 1 into a perl-script, so I don't need to remember these 2 commands:

#!/usr/bin/perl
use strict;

my @choices = ();
my $i = 0;
for (`pacmd list-sinks`) {
    if( /name:.*<(.+)>/) {
        $choices[$i++] = $1;
        print "$i:\t$1\n";
    }
}
my $choice = $choices[<>-1] or die "invalid choice";
exec (qw(pacmd load-module module-remap-sink sink_name=mono),
    "master=$choice",
    qw(channels=2 channel_map=mono,mono));

(I would've annotated that answer, but my karma is to low ;-) )

Answer 3

It seems there is no easy way to do this.

You can do it though, by proxying all PulseAudio output to a Jack sink. Too cumbersome to be used casually...

Answer 4

You might be able to use the pulseaudio sound settings manager to change stereo to mono. Or perhaps you can try just panning everything to the left or right speaker.