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Chroma Key works in fusion pvw, but breaks when rendered-

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MisterAmmaiu

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Chroma Key works in fusion pvw, but breaks when rendered-

PostTue Jan 14, 2025 2:12 am

Hello there!
I have been trying to use the Fusion tab in Resolve Studio 19.1.2 to apply a chroma key to a blue-ish screen in a doorway, such that the doorway is replaced with a gradient. In the Fusion page, this ends up looking like the following:
Image

However, when I export from the Deliver tab, the resultant video ends up containing a partially-failing chroma key that looks something like this:
Image

This was exported with the below settings:
Image
Image

If it's helpful, I've pasted my nodes below, most of which are static images used to clean up the chroma key (i.e. chair, lamp, light, person, etc.). I do have some currently unused polygon nodes that I kept in case I needed them again, but they aren't hooked up to anything.
Image

On the Deliver tab, I tried playing around with different formats and codecs, as well as setting key frames from automatic to 1, but to no avail. I'm very much a novice when it comes to the depths of resolve compositing and rendering, so any help or pointers would be greatly appreciated!
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MisterAmmaiu

  • Posts: 2
  • Joined: Tue Jan 14, 2025 1:49 am
  • Real Name: Mister Ammaiu

Re: Chroma Key works in fusion pvw, but breaks when rendered

PostTue Jan 14, 2025 10:27 pm

Okay so for those who may find it useful, I figured out the issue.

The fix is that, at least while compositing and rendering the chroma-keyed clip, disable optimized media. At the global level that can be done by going to Playback > Use Optimized Media if Available and ensuring it is unchecked.
Image

For me, this meant that the Fusion tab now matched the rendered export, where the key was not keying out the desired color completely. You can then adjust the key to cover missed regions, then export, and finally get the desired region entirely keyed out as expected.

I'm not familiar with the internal workings of Resolve, but I'm guessing the cause of this issue has to do with the color range of the compressed optimized footage being smaller and thus easier to key than the uncompressed raw footage. So, when applying a chroma key to optimized footage in Fusion, the key becomes calibrated to the "easier-to-key" optimized footage. Then, when rendered in export, the uncompressed raw footage is used. This is sorta "harder-to-key" due to its increased color range, and so the key calibrated to the compressed footage may drop out occasionally on the raw footage, which is exactly what I was seeing in the render.

Hopefully this helps someone down the line! I'm happy to have found the issue and glad it was fixable!

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