Quick Summary (TL;DR)
If your EasyWorship Alpha Key outputs look slightly transparent when using HDMI-to-SDI converters with a Blackmagic ATEM, the issue is usually a mismatch between RGB full range (0–255) and YCbCr limited range (16–235). Fix it by configuring your GPU to output YCbCr422, Limited, 8 bpc. This ensures clean, opaque overlays in church production and streaming.
Introduction and Overview
This is the third article in our 4-part series on EasyWorship Alpha Key workflows for church production and live streaming. In Part 2, we covered why churches need to convert HDMI to SDI. In this article, we’ll look at why transparency problems happen when converting HDMI to SDI, how to fix them with the right GPU settings, and which converters work best.
The Alpha Key Conversion Problem
When EasyWorship outputs dual signals:
- Fill: Full-color graphics (lyrics, lower thirds, scripture).
- Key: Grayscale matte for transparency.
…these are sent over HDMI to converters like the Decimator MD-HX or Blackmagic Up/Down Cross Converter. The issue? Pure white in the key signal doesn’t equal pure white in SDI. This results in overlays that look slightly transparent instead of fully opaque.
Partially Transparent
Fully opaque
Why It Happens
- HDMI (GPU default): Outputs RGB full range (0–255) for monitors.
- SDI (broadcast standard): Expects YCbCr 4:2:2 limited range (16–235 luma, 16–240 chroma).
- Converters: Remap 0–255 into 16–235, but this scaling isn’t always perfect. Whites (255) may land below 235.
(This limited range exists to preserve headroom and footroom from the analog broadcast era.)
The Fix: Configure GPU to Output Broadcast-Legal Video
Instead of letting converters handle scaling, configure your GPU to output the correct format.
Recommended NVIDIA GPU Settings
- Desktop color depth: 32-bit
- Output color format: YCbCr422
- Output color depth: 8 bpc (10 bpc if supported by your chain)
- Output dynamic range: Limited (16–235)
Pro tip: If your converters and mixer support it, try 10-bit YCbCr 4:2:2 for smoother gradients.
Troubleshooting Transparency Problems
If your EasyWorship overlays look wrong after HDMI-to-SDI conversion, check for these symptoms:
- Lyrics or text look washed out or semi-transparent
- White areas don’t appear fully solid
- Keyed elements shimmer or fade slightly
Fix: Confirm GPU is set to YCbCr422, Limited, 8 bpc, and test with a white block to verify full opacity.
Quick Fix Checklist
☐ Set NVIDIA GPU to YCbCr422, Limited
☐ Use 8 bpc (or 10 bpc if supported end-to-end)
☐ Test with gradient or solid white patterns
☐ Choose converter (Decimator = ease, Blackmagic = cost savings)
Key Takeaways
- Transparency issues come from RGB vs YCbCr mismatch.
- Configure GPU for broadcast-legal output to fix.
- Decimator = ease of use, Blackmagic = lower cost.
- With correct settings, EasyWorship outputs look crisp and professional on IMAG and streams.
Wrap Up
For houses of worship, HDMI-to-SDI conversion can cause frustrating transparency issues in Alpha Key workflows. By setting your GPU correctly and using the right converter, you’ll ensure lyrics, scripture, and sermon overlays are fully opaque and professional-quality.
This concludes Part 3. In Part 4, we’ll cover how to sync key and fill outputs so your overlays stay artifact-free in worship production.
Final Note: EasyWorship was built for church production. With GPU settings dialed in and HDMI-to-SDI handled correctly, your Alpha Key overlays will integrate seamlessly with broadcast gear like the Blackmagic ATEM, ensuring distraction-free worship visuals.
