[pulseaudio-discuss] Recording from USB devices without channel mixing

[Tanu Kaskinen]

On Mon, 2016-02-29 at 14:23 +0100, Klaus Jaensch wrote:
> Hello,
> 
> we use USB audio devices (e.g. M-Audio Fast Track and Focusrite Scarlett 
> 2i2) to record mono speech on Ubuntu.
> We face the problem that for mono recordings both input channels of the 
> devices are mixed together. But we want to record only the left channel, 
> not the mix. The left channel gets only half of the dynamic range; the 
> signal amplitude does not exceed -6dB.
> 
> Is there a way to configure PulseAudio accordingly?

If the recording program allows, you can specify its channel map to be
"left" instead of "mono". For example, parecord supports the --channel-
map option.

If the recording program forces you to use "mono" channel map, you can
use module-remap-source:

pactl load-module module-remap-source sink_name=mono_source master=... channel_map=mono master_channel_map=left remix=no

The "master" argument is the source name of the usb sound card. You can
find the name with "pactl list sources". Once the remap source is
loaded, you can point the recording program to "mono_source".

-- 
Tanu