Creating a null sink

Getting familiar with pactl

First we want to take a look at all output channels (or sinks):

➜  ~ pactl list short sinks
1       alsa_output.pci-0000_1f_00.3.iec958-stereo      module-alsa-card.c      s16le 2ch 44100Hz       SUSPENDED
2       alsa_output.pci-0000_1d_00.1.hdmi-stereo-extra1 module-alsa-card.c      s16le 2ch 44100Hz       SUSPENDED
3       bluez_sink.38_18_4C_BE_25_8B.a2dp_sink  module-bluez5-device.c  s16le 2ch 44100Hz       RUNNING

Sink 3 are my bluetooth headphones, so I want to use those later to output all sounds.

In case the naming isn't as obvious in your case, you can look at pavucontrol which should show you, which sink you are using at the moment. (While you are playing audio, the last column should also say RUNNING)

Creating a null sink

A null sink is a output channel that doesn't correspond to a hardware device. Later we will use it to tell OBS to only stream audio from this channel.

➜  ~ pactl load-module module-null-sink
28

As null is an ugly name, we will set this channel's description to OBS (so this is what pavucontrol and your desktop environments audio settings will show you).

➜  ~ pacmd update-sink-proplist null device.description=OBS
➜  ~ pactl list short sinks
1       alsa_output.pci-0000_1f_00.3.iec958-stereo      module-alsa-card.c      s16le 2ch 44100Hz       SUSPENDED
2       alsa_output.pci-0000_1d_00.1.hdmi-stereo-extra1 module-alsa-card.c      s16le 2ch 44100Hz       SUSPENDED
3       bluez_sink.38_18_4C_BE_25_8B.a2dp_sink  module-bluez5-device.c  s16le 2ch 44100Hz       RUNNING
4       null    module-null-sink.c      s16le 2ch 44100Hz       SUSPENDED