Skip to main content

B4 Video Return


The goal is to use RET, VTR buttons on B4 lenses to be able to act on the video return from the switcher.

Camera set up

The first step is to configure the camera and the lens.

Here, I created a Dreamchip AtomOne with a Canon B4 lens:

  • On the web UI Configuration, in Camera, click on +
  • Create your camera as usual, here I used a Dreamchip AtomOne
  • Add your lens as usual, here I used B4 Generic on my CI0-12-137, port 2

You can find more information:

  • on Dreamchip camera setup here.
  • on B4 lens set up here.

Switcher set up

The second step is to configure the switcher and link my camera (configured above) to the correct input.

Here, I created an ATEM switcher and linked my camera DC to the input 1.

You can find more information on various switcher/router integration here.

Ensure the link is working, the block should be green:

Now, navigate to /dev/app.html. If my RCP is RCP-18-4 and I use the URL:, then it is

Search for ATEM switcher (CTRL+F)

Click on the title, and you should see a panel on the right:

Set up the B4 video return by changing the field video_return (empty by default):

  • It is a list, separated by ;
  • Each item in this list follows the syntax : output:live_input,program_input,ret1_input,ret2_input
  • In this example: Aux5:1,2,3,4 means:
    • Aux5 : my monitor output on my ATEM
    • 1 : my camera is on input 1, input 1 is displayed when no button is pressed
    • 2 : input 2 is displayed when program button is pressed
    • 3 : input 3 is displayed when RET1 button is pressed
    • 4 : input 3 is displayed when RET2 button is pressed

Depending on the switcher, names can differ.

Here on my ATEM, output 5 is named as Aux5, on another router, it could be simply 5.

Refer to the configuration page of the RCP to ensure names match.