Split'n'Merge Audio

The aim of this project is to find a way to merge different sources of audio into a virtual mic.

DiscoBot

Check it here.

Jack

First step: try to install and run a JACK server.

https://wiki.archlinux.fr/Jack

If you find the message Could not open component .so '/usr/lib/jack/jack_firewire.so': libffado.so.2: cannot open shared object file: No such file or directory when starting JACK daemon, you might need to install a firewire driver (even if you don't have a firewire input): libffado.

A tad complex to put in place, let's look into Pulseaudio

Pulseaudio

The idea is to create a virtual mic virtualMic that merges the real mic and the music, as well as a virtual output virtualSp so that we can ear the music too.

1. Virtual sinks:

pactl load-module module-null-sink sink_name=virtualMic sink_properties=device.description=virtualMic
pactl load-module module-null-sink sink_name=virtualSp sink_properties=device.description=virtualSp

2. Add a loopback to virtualMic

pactl load-module module-loopback sink=virtualMic

3. Redirect the monitor of virtualSp to virtualMic

pactl load-module module-loopback sink=virtualMic source=virtualSp.monitor

4. Redirect the monitor of virtualSp to the real speakers as well.

pactl load-module module-loopback sink=alsa_output.pci-0000_00_1b.0.analog-stereo source=virtualSp.monitor

Where the name of the sink to which I want to redirect is listed through

pactl list short sinks
0       alsa_output.pci-0000_00_1b.0.analog-stereo      module-alsa-card.c      s32le 2ch 44100Hz       RUNNING
1       virtualMic      module-null-sink.c      float32le 2ch 44100Hz   RUNNING
2       virtualSp       module-null-sink.c      float32le 2ch 44100Hz   RUNNING

We can also give the last pactl command the id of the sink instead of its name.

5. In pavucontrol, set and check the following:

• Input Devices: default fallback on Monitor of virtualMic

• Output Devices: default fallback to your speakers.
• Recording:
  • Loopback to virtualMic from real mic
  • Loopback to virtualMic from Monitor of virtualSp
  • Loopback to speakers from Monitor of virtualSp
  • Recording app (Discord, Audacity, etc.) from Monitor of virtualMic

Check that they are all unmuted!

• Playback:
  • Loopback of real mic on virtualMic
  • Loopback from Monitor of virtualSp on virtualMic --> music to your virtual mic, this is the level to adjust for the broadcast only
  • Loopback from Monitor of virtualSp on speakers --> you can still ear your own music, changing this level will only update the volume for you
  • Output of your discussion app (Discord, etc.) on speakers
  • Music on virtualSp --> changing this level will modify the volume for you and the broadcast

Check the references for more details.

References

Adding Ambient Sounds to your Discord Server On LInux Share an audio playback stream through a live audio (video) conversation like Skype