Linux A/V sync

In my opinion having a good video conference setup is essential in a remote job. The consensus on the net is that webcams are terrible as … webcams. Instead, you get better quality using a compact camera with a capture card for the video and a separate microphone for audio. I use a Sony α5000 with an Audio-Technica at2020. Using separate devices for audio and video has as disadvantage they are no longer in sync.

Video setup

Using OBS you can easily expose the capture card as a virtual camera (you will also need the package v4l2loopback). Unfortunately the virtual camera devices provides no audio. On Mac and Windows there is the audio monitor plugin to get audio out of OBS allowing us to sync the audio in OBS. On Linux there is no way to get synchronized audio out of obs.

Sometimes obs will not start the virtual camera in a sandboxed environment (flatpak/snap etc). You can manually load the needed kernel module: modprobe v4l2loopback exclusive_caps=1 card_label='OBS Virtual Camera'

For some reason my camera’s white balance is off when using it as webcam. We can solve this using vl2-ctl (sudo apt install v4l-utils). It depends on your capture card/camera what you can change, a tweak to hue and saturation made a huge difference for me (I am no longer slightly green!).

Audio sync

For Linux there is EasyEffects to use it you will need to switch from PulseAudio to the newer PipeWire which is set to fully replace PulseAudio in the future. For Ubuntu a guide can be found guide. Then install EasyEffects, I use the flatpak as it comes with all audio plugins. I feel more comfortable if OBS can not claim the microphone therefore I disable all audio inputs in OBS (file -> settings -> audio)

In EasyEffects

  • Go to the Pipewire tab at the top of the screen.
    • Under input devices ensure your microphone is picked up as default of select your microphone manually
    • Under Output Devices ensure default is not selected and pick a device that can not output sound! On my machine EasyEffects outputs whatever comes in over the microphone to the output device leading to a feedback loop that gets painfully loud. Picking a device that does not output audio, such as an unplugged headphone port, ensures this won’t hurt you.
  • Go to the Input tab at the top of the screen. Now click the tab plugins
  • left top column Add Plugins add the delay plugin
  • toggle the button in the lower right corner to enable processing
  • use the spectrogram at the top to verify the delay is working (clap and see a delayed response in the spectrogram)
  • To use the now delayed sound choose the EasyEffects Source in your VoIP program.