Hologramu Hologramu

Choosing a cameraFree

Finding the right webcam — even when several devices show up.

The device listLinux

On Linux a single USB camera often reports several /dev/video* nodes, only one of which delivers pictures. Hologramu queries each device and hides the metadata-only nodes.

When the list stays empty

  • Is the camera held by another program?
  • Are the permissions on /dev/video* missing?

What the machine itself knows is shown by v4l2-ctl from the v4l-utils package (sudo pacman -S v4l-utils or sudo apt install v4l-utils):

bash
v4l2-ctl --list-devices

If the camera is listed there but not in Hologramu, membership in the video group is usually what is missing. Log out and back in after the second command.

bash
groups
sudo usermod -aG video $USER

A phone instead of a webcam

A phone makes a good camera — and a good second one. See Phone as a camera.

Preview

The preview window normally shows only points and lines. Show camera image in the preview adds the picture — but only until the tracker restarts.

TODO: Find out whether that is deliberately temporary, and state the reason here.