StudioPro Key and Fill

QuickLink StudioPro supports Key and Fill, essential for displaying semi-transparent graphics like lower thirds over live video feeds. This guide explains the concept and walks you through setup and usage within StudioPro.

Understanding Key and Fill

In broadcast production, Key and Fill are used to composite graphics over video in real time.. They are essential to chroma keying, layering, and compositing video sources. In video production, especially in live graphics compositing, the Key and Fill signals work together.

• Key (Alpha/Matte Channel) - Transparency or alpha information (what parts of an image/video should be visible or hidden).
  Defines transparency. Usually a grayscale signal where:
  • White (255)= Fully opaque
  • Black (0)= Fully transparent
  • Gray (1-254)= Partial transparency
• Fill (RGB Image Content)
  Contains the actual visual content (the graphic) that will be overlaid according to the transparency defined in the Key.

Together, the Key and Fill allow graphics to be composited cleanly over video in real time.

Key and Fill vs. DSK (Downstream Keyer)

• Key and Fill: Used to provide separate alpha (key) and video (fill) signals for external hardware to composite.
• DSK (Downstream Keyer): A switcher feature used to overlay graphics post-production path, often activated to toggle graphics like lower thirds, logos, or tickers.

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  StudioPro Configuration Steps

   

  1. Input Key and Fill to StudioPro

  Firstly, you need to add your SDI sources to the scenes. Use the Add Source option to bring in your SDI inputs for Key and Fill.

  Ensure your Decklink card or input hardware is correctly routing:

  • Key input to StudioPro via SDI (in this example we are using P3)
  • Fill input to StudioPro via SDI (in this example we are using P4)

   

  2. Preview Key input

  Switch to your P3 (Key) source to confirm the grayscale image defining transparency.

  

   

  3. Preview the Fill Layer

  Switch to P4 (Fill) and verify that your full-color graphic (base image) displays correctly.

   

  

   

   

  4. Apply a Dynamic Mask Filter

  To use the Key signal for transparency:

  • Go to the scene where the Fill signal is located. P4 input for this example
  • Select the source and navigate to: Filters
  • Click the "+" under Effect Filters
  • Select Dynamic Mask
  • Set the Input Source to the Key (P3)
  • Scroll down to the Alpha Channel section and apply the following;
  • Set Blue Input Value: 1
  • Set Base Input Value: 0

  ✅ This configures StudioPro to interpret the blue channel from the Key input as alpha transparency.

   

  

   

  5. Create DSK

  We can now create the DSK to be able to toggle the overlay on or off.

  To control when graphics appear:

  1. Select the scene with your Fill + Key setup.
  2. Open the DSK menu and click "+" to create a new DSK.

  Use the DSK toggle during live production to show/hide the graphic overlay.

  

   

  Key and Fill should now be successfully set up and ready to apply.

   

  Live Use Example: Interview Feed

  When monitoring a live production, use the DSK (Downstream Keyer) toggle:

   

  DSK OFF

  • The video feed appears without the graphic overlay.

   

   

  

   

   

  DSK ON

  • The key and fill graphics are composited over the video feed (e.g. lower third titles shown).

  

   

  Summary

  With the proper SDI routing and Dynamic Mask filter applied, StudioPro outputs graphics with transparency, leveraging the SDI card's Key and Fill capabilities. This setup is essential for professional broadcast overlays.

  This article was created to explain "Key and Fill" using NewBlue SDI output but also be used with other platforms.