Easiest way to record mic and line in simultaneosly and without pain?

Question

I'm using Arch Linux with alsa, pulseaudio, pavucontrol, jack, and whatever else. I want to record a microphone and a guitar simultaneously no matter how low level I should get. There are several posts on how to create a virtual pulseaudio sink with two channels linked to rear mic on one channel and line in on the other and connected to the monitor or connecting jack sinks, but nothing make sense in my current setup.

My default.pa file is

#!/usr/bin/pulseaudio -nF
#
# This file is part of PulseAudio.
#
# PulseAudio is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# PulseAudio is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with PulseAudio; if not, see <http://www.gnu.org/licenses/>.

# This startup script is used only if PulseAudio is started per-user
# (i.e. not in system mode)

.fail

### Automatically restore the volume of streams and devices
load-module module-device-restore
load-module module-stream-restore
load-module module-card-restore

### Automatically augment property information from .desktop files
### stored in /usr/share/application
load-module module-augment-properties

### Should be after module-*-restore but before module-*-detect
load-module module-switch-on-port-available

### Load audio drivers statically
### (it's probably better to not load these drivers manually, but instead
### use module-udev-detect -- see below -- for doing this automatically)
#load-module module-alsa-sink
#load-module module-alsa-source device=hw:1,0
#load-module module-oss device="/dev/dsp" sink_name=output source_name=input
#load-module module-oss-mmap device="/dev/dsp" sink_name=output source_name=input
#load-module module-null-sink
#load-module module-pipe-sink

### Automatically load driver modules depending on the hardware available
.ifexists module-udev-detect.so
load-module module-udev-detect
.else
### Use the static hardware detection module (for systems that lack udev support)
load-module module-detect
.endif

### Automatically connect sink and source if JACK server is present
.ifexists module-jackdbus-detect.so
.nofail
load-module module-jackdbus-detect channels=2
.fail
.endif

### Automatically load driver modules for Bluetooth hardware
.ifexists module-bluetooth-policy.so
load-module module-bluetooth-policy
.endif

.ifexists module-bluetooth-discover.so
load-module module-bluetooth-discover
.endif

### Load several protocols
.ifexists module-esound-protocol-unix.so
load-module module-esound-protocol-unix
.endif
load-module module-native-protocol-unix

### Network access (may be configured with paprefs, so leave this commented
### here if you plan to use paprefs)
#load-module module-esound-protocol-tcp
#load-module module-native-protocol-tcp
#load-module module-zeroconf-publish

### Load the RTP receiver module (also configured via paprefs, see above)
#load-module module-rtp-recv

### Load the RTP sender module (also configured via paprefs, see above)
#load-module module-null-sink sink_name=rtp format=s16be channels=2 rate=44100 sink_properties="device.description='RTP Multicast Sink'"
#load-module module-rtp-send source=rtp.monitor

### Load additional modules from GConf settings. This can be configured with the paprefs tool.
### Please keep in mind that the modules configured by paprefs might conflict with manually
### loaded modules.
.ifexists module-gconf.so
.nofail
load-module module-gconf
.fail
.endif

### Automatically restore the default sink/source when changed by the user
### during runtime
### NOTE: This should be loaded as early as possible so that subsequent modules
### that look up the default sink/source get the right value
load-module module-default-device-restore

### Automatically move streams to the default sink if the sink they are
### connected to dies, similar for sources
load-module module-rescue-streams

### Make sure we always have a sink around, even if it is a null sink.
load-module module-always-sink

### Honour intended role device property
load-module module-intended-roles

### Automatically suspend sinks/sources that become idle for too long
load-module module-suspend-on-idle

### If autoexit on idle is enabled we want to make sure we only quit
### when no local session needs us anymore.
.ifexists module-console-kit.so
load-module module-console-kit
.endif
.ifexists module-systemd-login.so
load-module module-systemd-login
.endif

### Enable positioned event sounds
load-module module-position-event-sounds

### Cork music/video streams when a phone stream is active
load-module module-role-cork

### Modules to allow autoloading of filters (such as echo cancellation)
### on demand. module-filter-heuristics tries to determine what filters
### make sense, and module-filter-apply does the heavy-lifting of
### loading modules and rerouting streams.
load-module module-filter-heuristics
load-module module-filter-apply

### Make some devices default
#set-default-sink output
#set-default-source input

For example i found this bash script to accomplish the first:

 #!/bin/bash

 #    Script to map two pulseaudio hardware input sources as mono inputs
 #    to left and right channel of a new loopback-sink respectively. This
 #    sink can be used e.g. to use VoIP or record two microphones seperately.
 #    Copyright (C) 2013, Henning Hollermann, [email protected]
 #
 #    This program is free software: you can redistribute it and/or modify
 #    it under the terms of the GNU General Public License as published by
 #    the Free Software Foundation, either version 3 of the License, or
 #    (at your option) any later version.
 #
 #    This program is distributed in the hope that it will be useful,
 #    but WITHOUT ANY WARRANTY; without even the implied warranty of
 #    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 #    GNU General Public License for more details.
 #
 #    You should have received a copy of the GNU General Public License
 #    along with this program.  If not, see <http://www.gnu.org/licenses/>.

 do_activate() {
     while [ "x" = "x$LEFT" ]; do
         echo "Choose Source for left channel by ID"
         pactl list short sources
         read ID
         LEFT=$(pactl list short sources|awk '/^'$ID'/{print $2}')
     done
     while [ "x" = "x$RIGHT" ]; do
         echo "Choose Source for right channel by ID"
         pactl list shrot sources | grep -v $LEFT
         read ID
         RIGHT=$(pactl list short sources | grep -v $LEFT|awk '/^'$ID'/{print $2}')
     done
     # Create the name of the Combined sink
     NAME="Combined_Mics:_Left:_"$(echo $LEFT|awk -F'.' '$0=$2')"_Right:_"$(echo $RIGHT|awk
 -F'.' '$0=$2')

     echo "[LOAD] null sink as \"$NAME\" to connect the two mics to"
     pactl load-module module-null-sink \
             sink_name=combined channels=2 \
             sink_properties="device.description=$NAME"

     echo "[LOAD] map source 1 ($LEFT) to left channel of \"$NAME\""
     pactl load-module module-remap-source \
             source_name=${LEFT}_left_channel master=$LEFT channels=2 \
             master_channel_map=mono,mono channel_map=left,left
     pactl load-module module-loopback sink=combined source=${LEFT}_left_channel

     echo "[LOAD] map source 2 ($RIGHT) to right channel of \"$NAME\""
     pactl load-module module-remap-source \
             source_name=${RIGHT}_right_channel master=$RIGHT channels=2 \
             master_channel_map=mono,mono channel_map=right,right
     pactl load-module module-loopback sink=combined source=${RIGHT}_right_channel
     echo "[DONE] Now adjust the left and right channel volume of the new sink to be equally
 loud"
 }

 do_deactivate() {
     echo "[UNLOAD] pulseaudio modules..."
     echo "[UNLOAD] module-loopback"
     pactl unload-module module-loopback
     echo "[UNLOAD] module-remap-source"
     pactl unload-module module-remap-source
     echo "[UNLOAD] module-null-sink"
     pactl unload-module module-null-sink
 }

 init() {
     for exe in /usr/bin/pulseaudio /usr/bin/pactl; do
         if [ ! -x "$exe" ]; then
             echo "[ERROR] required file $exe not found or not  executable"
             exit 1
         fi
     done
     [ ! -x /usr/bin/pavucontrol ] && echo "[NOTICE] pavucontrol might be very useful."
 }

 # MAIN
 init;
 case $1 in
 activate|enable|start)
     do_activate;;
 deactivate|disable|stop)
     do_deactivate;;
 *)
     echo "Usage: $0 [enable|disable]";;
 esac;

but which is in the script:

$ pactl list short sources
 0  alsa_output.pci-0000_00_1b.0.analog-stereo.monitor  module-alsa-           card.c   s16le 2ch 44100Hz   RUNNING
 1  alsa_input.pci-0000_00_1b.0.analog-stereo   module-alsa-card.c  s16le 2ch 44100Hz   RUNNING

but what i need is something like:

$ pactl list sources|grep input
Name: alsa_input.pci-0000_00_1b.0.analog-stereo
    analog-input-front-mic: Front Microphone (priority: 8500, not   available)
    analog-input-rear-mic: Rear Microphone (priority: 8200, not available)
    analog-input-linein: En línea (priority: 8100, not available)
Puerto Activo: analog-input-front-mic

which are not devices but ports. output from arecord is

 $ arecord -l
 **** List of CAPTURE Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: VT1708B 8-Ch Analog [VT1708B 8-Ch Analog]
  Subdevices: 0/1
  Subdevice #0: subdevice #0

So, how could i access those ports either through alsa or through pulseaudio? Or even should be a more straight forward solution like:

$ arecord 1 channel1.wav&arecord 2 channel2.wav

Answer 1

Your soundcard only has one capture device. That means you can only record from one port at a time.

I have used a CM108 USB sound card and my internal sound card to record simultaneously without any problems though.