To once again explain my situation, I use OBS also for video conferencing, through the virtual camera¹. OBS does not offer a built-in way to provide a virtual microphone with all the filters and such applied as well (in my case noise reduction and a limiter), so I need to solve this in a separate way. Additionally, my camera setup has a small delay of around 350ms that I also need to compensate by delaying my audio.

OBS offers a monitoring port that you can push your audio devices on, and that will get the filters applied, but none of the configured offsets. On Windows, I solved this by using a combination of two Virtual Cable devices and RadioDelay between the two.

Today I rebuild basically the same setup on Linux via a bunch of virtual Pulseaudio devices. I have this in ~/.local/bin/obs-virtual-mic:

#!/bin/bash

# create virtual speaker
pactl load-module module-null-sink sink_name=Virtual-Speaker sink_properties=device.description=Virtual-Speaker

# create delayed virtual speaker & associated mic
pactl load-module module-null-sink sink_name=Virtual-Speaker-Delayed sink_properties=device.description=Virtual-Speaker-Delayed
pactl load-module module-remap-source source_name=Remap-Source master=Virtual-Speaker-Delayed.monitor

# copy from virtual to delayed virtual with 350ms delay
pactl load-module module-loopback latency_msec=350 source=Virtual-Speaker.monitor sink=Virtual-Speaker-Delayed

Let’s take a closer look at what this does:

• create two virtual sinks Virtual-Speaker and Virtual-Speaker-Delayed with pactl load-module module-null-sink ...
• create a virtual source for the delayed sink via pactl load-module module-remap-source ...
• finally mirror the sound from Virtual-Speaker.monitor to Virtual-Speaker-Delayed while adding a latency of 350ms

I run this. Then OBS gets set to use Virtual-Speaker as monitor. In my video conferencing software I then use Virtual-Speaker-Delayed as my input to get my video and audio synced up.

OBS used for video conferences through the virtual camera. Audio virtualized and with active OBS filters applied (limiter, noise suppression) through means of setting the monitor device to a sink created with VirtualCable and using its source in the video conferences tools.

Problem

The camera feed has a slight delay of 300-400ms. The audio is thus ahead.

Adding a delay through OBS doesn’t get applied to the monitor device (Source):

The sync offset that you apply in OBS only applies to either the recording from OBS or the output stream from OBS. It does not apply to the monitor. When you use a virtual cable, and you set it up as a monitor in OBS, you will hear the inputs without any sync delay. As far as I know there is no way to apply your delays to the audio monitor output.

Solution

Install RadioDelay.

Create a second virtual cable device. Use its sink as the monitoring device in OBS, its source as source in RadioDelay, and set the sink of the first virtual cable as sink in RadioDelay. Apply the delay in RadioDelay.

The first cable now outputs delayed audio and can be used as audio source in the video conferencing tools.

You can also create a shortcut to fire up RadioDelay with the right devices selected, the delay applied and the output active with something like this:

"C:\Program Files\Radiodelay\radiodelay.exe" -delay 0.3 -in 5 -out 3

in and out are the positions of the audio device in the drop-down list. delay is the delay in seconds.

Can of course also be used without OBS.

edit 2023-03-11: Here’s how I solved the same problem under Linux.