I'm trying to figure out FCP and it's built in keyer. This is 720p HDV imported with clipwrap off a Firestore. I'm using ProRes422 on the timeline. When I render the clip with a static background I get this line on the subject's face and on her left hand. The source footage doesn't have this line. What's causing it?

I'm also trying to deal with the green/red ghosting.

That's very strange. Which key filter are you using? Does the line occur if you make a still frame of the live action footage and key that? Are you using any other filters at the same time?

That's very strange. Which key filter are you using? Does the line occur if you make a still frame of the live action footage and key that? Are you using any other filters at the same time?

I'm using color smoothing, 8 point garbage matte, chroma keyer.

The line only appears after render, when I muted the background plate and unrendered the clip, the line vanishes.

This is 720p HDV transcoded to proress422.

I'm sure you have tried this already but remove the color smoothing and the garbage matte and see what happens. Also try flipping the order of the filters. I've never seen this problem in a chroma key before but I do know that sometimes additional filters have to be in a certain order or the key doesn't work.

If you key in front of another background and render do you still have the problem?

I unchecked the smoothing filter and rerendered and the stripe disappeared.