Preview Cam

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Using it with OBS ​

Preview Cam is independent of OBS Studio: it opens the camera for itself and changes nothing on the device. There are a few things worth knowing when you use both.

Sharing one webcam ​

Whether two applications can read the same physical webcam at once depends on the camera driver and on which application opened it first. If the camera is taken, the overlay says Camera in use instead of showing an empty window.

The reliable setup is to let one application own the webcam and have the others read a virtual camera:

  • NVIDIA Broadcast owns the webcam; OBS and Preview Cam both use Camera (NVIDIA Broadcast).
  • OBS owns the webcam; start Virtual Camera in OBS and select OBS Virtual Camera in Preview Cam.

Any camera Windows lists can be selected in Settings → Camera → Device.

Getting the overlay into a recording ​

Display Capture records the overlay like everything else on screen. If you capture a single window instead, the overlay is not part of that window, so add it to the scene in one of these ways.

This gives OBS exactly what the overlay shows — cropped, mirrored and in the same shape — with a real alpha channel, so rounded corners, the circle and a removed background stay transparent.

  1. In Preview Cam: Settings → Camera → Virtual camera for OBS → on.
  2. In OBS: Sources → + → Video Capture Device.
  3. In the Device list choose Preview Cam.

The camera delivers ARGB video only, so OBS always receives the alpha channel. If the corners still look filled after updating Preview Cam, OBS is using the previous version of the camera: remove the source and add it again, or restart OBS.

Good to know:

  • The hover controls and messages are not part of the picture.
  • The picture has the overlay's proportions at the camera's resolution, for example 1080 × 1080 for a circle from a 1080p camera. After changing the shape, deactivate and reactivate the source in OBS to pick up the new size.
  • While Preview Cam is not running, or the overlay is hidden, the device delivers a transparent picture.

Window Capture ​

  1. In Preview Cam: Settings → Behavior → Allow window capture → on (the default).
  2. In OBS: Sources → + → Window Capture and choose [preview.exe]: Preview Cam.

OBS draws captured windows opaque, so the area outside a rounded or circular shape comes out black. Use the virtual camera when you need transparency.

The camera directly ​

Add a Video Capture Device source and pick the same camera the overlay uses. You get the plain rectangular picture and shape it with OBS filters; Preview Cam is then only your own on-screen monitor.

Transparent background with NVIDIA Broadcast ​

  1. In NVIDIA Broadcast: Virtual background → Remove.
  2. In Preview Cam: select Camera (NVIDIA Broadcast).
  3. Settings shows ARGB32 · with transparency when it is active.

Turn Transparent background off in Settings if you prefer a black background.