Map MIDI CC to OBS Chroma Key Tolerance

Controlling your green screen settings in real-time can significantly improve the quality of your live stream. This article provides a step-by-step guide on how to map a physical fader or knob on an external MIDI controller to smoothly adjust the chroma key tolerance (similarity and smoothness) in OBS Studio. By using a specialized OBS plugin, you can bypass manual mouse adjustments and achieve seamless, hands-on control.

Step 1: Install the OBS MIDI MG Plugin

OBS Studio does not support MIDI controllers natively for granular filter adjustments. To enable this functionality: 1. Download the obs-midi-mg plugin from the official OBS Studio resources forum. 2. Install the plugin by running the installer or extracting the files into your OBS Studio installation directory. 3. Restart OBS Studio to activate the plugin.

Step 2: Set Up Your Chroma Key Filter

Ensure your camera source has the chroma key filter applied: 1. Right-click your camera or capture card source in the Sources dock and select Filters. 2. Click the + icon under “Effect Filters” and select Chroma Key. 3. Name the filter (e.g., “Chroma Key”) and close the window.

Step 3: Configure Your MIDI Device in OBS

  1. Open OBS Studio and navigate to the top menu. Go to Tools and select OBS MIDI MG Setup.
  2. In the Devices tab, locate your connected external MIDI controller under the “Input” section.
  3. Check the Active box next to your controller to enable it.

Step 4: Bind the MIDI CC to the Chroma Key Tolerance

  1. Switch to the Bindings tab in the OBS MIDI MG setup window.
  2. Click Add Binding.
  3. Move the physical knob, fader, or wheel on your MIDI controller that you wish to use. The plugin will automatically detect the incoming MIDI CC (Continuous Controller) message and channel.
  4. In the Action dropdown menu, select Set Source Filter Value.
  5. Select your camera source, then select your “Chroma Key” filter from the respective target dropdowns.
  6. In the parameter dropdown, select Similarity (which controls the primary color range tolerance) or Smoothness.
  7. Adjust the scale limits. Because MIDI CC sends values from 0 to 127, map these to the appropriate filter scale (typically 1 to 1000 for similarity) to ensure the physical sweep of your controller translates to a smooth, usable range in OBS.
  8. Click Save.

You can now slide your MIDI fader or turn the knob to dynamically adjust the green screen tolerance on the fly, allowing you to instantly compensate for changes in studio lighting.