I am using Kdenlive v21.12.1 on Windows 10. I am trying to use the Rotoscoping effect to change the background in my video but it's not working for me. I've placed the effect on the "foreground" clip in the top track and selected the area that I want to keep, and I have the desired background in the second track. When the rotoscoping mode is set to Alpha, nothing happens at all, I just see the video from the top track (and nothing changes if I try changing the Alpha Operation). When I change the mode to Luma, the foreground becomes all white and the rotoscoped area is all black. When I change the mode to RGB, the foreground returns to the correct clip, but the rotoscoped area is still just black rather than the clip on the lower track.

At first I thought the problem might be caused by me using a still image as the background instead of an actual video clip, but when I put a video in there to test it out nothing changed, so it looks like that's not the problem.

Can anyone suggest what might fix this?

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Also, separate question while I'm thinking about it - is there a way to rotoscope two different areas in the same clip? I'm going to need to do that, if I can get this working in the first place.

if i can suggest... please use an updated build (there was a lot of fixes on last years) : https://download.kde.org/stable/kdenliv ... 2.04.3.exe

Thanks for the link. No luck though - I installed the new version, verified that that's what was running, but still the same problem. Or should I start again with a new project to make sure no bugs got saved with the old one?

EDIT: I did delete the old project and start a new one, and it worked! When I added the "foreground" video to the project it gave me an error message about not being able to edit until it converted it to a different format, so I'm guessing that was the problem all along. It did convert it automatically (I just had to select the new format), and after that I got exactly the effect I wanted.

So coming back to my other question, is there a way that I can apply the effect to two different parts of the screen at the same time? My specific example is that I'm playing guitar in the video, and there's a closed loop between my arm, the neck of the guitar, and the strap. If I can, I'd like to have my rotoscoped background inside that loop, and also outside of it, without just erasing the guitar strap. Any advice on how I can accomplish this?

EDIT 2: I dug around a little more and found the answer to my second question here - viewtopic.php?t=171848
the TLDR for anyone else who wants it is to add a second rotoscope to the same clip but change the function to Add instead of Write on Clear. I tested it out and got what I was looking for.

nice .. yep any variable frame rate clip need now a "transcoding" to prevent audio/video de-sync