obs

Configures OBS Studio for application demos from the host it runs on: encoder, canvas, webcam, recording and streaming profiles, branded scene collections, and a virtual camera for web meetings.

Requirements

• Arch Linux or CachyOS with the 22_obs group installed: OBS Studio, PipeWire Pulse, WirePlumber, the Hyprland portal backend, qt6-wayland, v4l-utils, v4l2loopback-dkms, obs-backgroundremoval (AUR), simde and ttf-montserrat. simde is a build requirement of every OBS 33 plugin that the AUR recipe does not declare.
• A Hyprland session to size the canvas; without one it falls back to 1920x1080.
• Privilege escalation (become: true) for the virtual camera and the Firefox policy.

Role Variables

Host detection

The role reads the host before writing anything:

• Encoder: the GPU that renders the desktop (boot_vga) encodes. A hybrid laptop uses VAAPI on its iGPU and the NVIDIA GPU stays asleep; a desktop whose screens hang off NVIDIA uses NVENC. A five-frame ffmpeg encode proves the choice, and x264 is used when it fails, with a preset sized to the CPU thread count.
• Video: the canvas is 16:9 at the native height of the largest external output from hyprctl monitors, scaled with Lanczos to obs_output_height in the streaming profile; the recording profile keeps the canvas size. The frame rate is 60 with a hardware encoder on a 60 Hz screen, 30 otherwise.
• Webcam: every /dev/video* node is listed and only colour capture nodes (MJPG or YUYV) are kept, so infrared and metadata nodes are skipped. External cameras win over integrated ones. The source uses the /dev/v4l/by-id link, else by-path, in MJPEG up to 1280x720 at 30 fps: YUYV at 1080p drops to 5 fps on USB 2. Without a camera the scenes get no Caméra source and the run warns: plug it in and run again with -e obs_config_force=true.
• Recordings: hybrid MP4 in $(xdg-user-dir VIDEOS)/OBS.

Webcam background

With obs-backgroundremoval installed, cutout makes the background transparent so the person sits directly on the scene; the camera then has no accent frame and touches the bottom edge. rvm (Robust Video Matting) works at 320x192 and remembers the previous frames. It gives a soft alpha that follows hair, so the plugin's threshold stays off. It runs on the CPU with four threads, or two below 8 threads, so the NVIDIA GPU stays asleep.

mediapipe segments at 256x144: on a 720p camera its mask shows stair-stepped edges. With it the mask is thresholded towards hiding the room (obs_webcam_threshold, plugin default 0.5) and obs_webcam_edge_trim trims the room's halo. The contour filter keeps the upstream 0.05, since a larger value merges small background areas, such as the gap under an arm, into the person.

blur keeps a blurred background in a framed inset, none the raw picture. Unchanged frames and a hidden camera skip inference. The plugin is built against the installed OBS: rebuild it with yay after an OBS upgrade if OBS reports it as not loaded.

Profiles and scenes

"Enregistrement" records the native canvas at constant quality. "Streaming" scales to obs_output_height at a constant bitrate, and its recordings reuse the stream encoder, so a stream is encoded once.

Each palette gets its own scene collection with Montserrat titles. Sombre (#FFFFFF on #242428) and Clair (#2A3235 on #FFFFFF) follow the brand guide with the primary colour #41A890; Gruvbox (#EBDBB2 on #1D2021, accent #83A598) matches the desktop. The primary colour draws the title underline and the camera frame. Scenes: intro (title and camera), screen with a camera inset, screen only, one application window on a backdrop with the camera, camera only, and a pause card. Desktop audio and the microphone are global sources.

Screen and window captures go through the XDG portal: Wayland gives no way to name the output in advance, so OBS asks once and keeps a restore token.

Titles need the static Montserrat weights from ttf-montserrat: OBS opens the first face of a font file, which is the Thin instance of the variable font from Google Fonts. The run warns when no static Bold face exists.

OBS rewrites these files when it exits, so the role creates them once and then leaves them alone. obs_config_force=true regenerates them and keeps the previous files as backups. The run refuses to regenerate while OBS is open.

Virtual camera

The virtual camera serves Teams and other web meetings. The role writes /etc/modprobe.d/zz-dotfiles-v4l2loopback.conf with exclusive_caps=1 (Chromium lists the device only with it) and loads the module now and at every boot. A module already loaded with other options is not unloaded, since that would cut a running camera; the run prints the reload command instead.

Firefox asks PipeWire for cameras, and PipeWire never adds a camera for this device: it checks the device at boot, before OBS writes to it, when it only accepts output. When Firefox is installed, the role writes the policy media.webrtc.camera.allow-pipewire = false as a default value, still editable in about:config. Other policies in the file are kept, and invalid JSON stops the run.

Start the virtual camera from the OBS Controls dock before the meeting, then pick "OBS Virtual Camera" in the browser. It carries no sound: pick the microphone in the meeting as usual.

Tags: obs, obs_config, obs_virtualcam.

Dependencies

None. The packages role installs 22_obs; the obs.yml playbook runs both.

Example Playbook

- hosts: all
  become: true
  roles:
    - role: obs
      when: "'22_obs' in packages_selected_groups"
      tags: [obs]

License

Unlicense

Author Information

pad