Project with two different frame rates - how to keep all frames


I have quite specific situation.

I have my main project with 30 frames per second. And it’s ok for most pieces of videos I would like to put here but with one exception (I don’t want to modify my main project frames rate). There is one very specific video registered with 50 frames per second and it’s some kind of rainbow blinking. Skipping some frames makes this rainbow to look very strange, thus I would like to keep all 50 frames. My idea is to just display this video with lower speed. More precisely the original piece of video has 49 seconds with 50 frames thus I would like to have it in my project to have around 82 seconds (more precisely 81.66666666…, but in this way all frames would be kept without skipping). However after adding it to the project it still has 49 seconds (thus shotcut automatically skips part of frames to have the same lenght).

My first idea was to set for this piece of video the speed 0.6 in properties tab (50*0,6=30) thus I would expect that this would give me the expected result (I would expect that lower speed will cause shotcut to keep all frames and will give me the video lenght around 82 seconds). But unfortunately it doesn’t seem to be true. The video lenght is extended to almost 82 seconds but the video still looks strange. It looks like that first shotcuts skips some frames and then when changing the speed it duplicates some frames instead of using those previously skipped frames).

Is there any way to solve this?

Or do you perhaps know any external program which would modify this video file properties to make it longer but with 30 frames per second instead of 50 frames per second?

Any ideas please?

This is exactly what I would have recommended to do.

What is your project video mode set to? Perhaps your project is not actually operating in 30fps.

Select File->Settings->Video Mode and select the specific video mode that you intend to use.

Something to test…

Start a brand new project with a 50fps Video Mode. Drop in the rainbow clip. Step through it frame at a time. Is every frame unique? Or is that 50fps clip actually a 25/30fps clip that was scaled up to 50fps and has its own duplication in the clip itself?

I would have expected the 0.6x speed technique you did to work exactly as you hoped. I’m curious if something fishy is going on with the source clip.

Another option is to use Shotcut 21.05.01 or later, create a new 30fps project, and import just the 50fps clip. Add a Time Remap filter to it and change the mode to Blend. Export as an intermediate file and bring it into your main project.

The idea behind Time Remap with blend mode is to get back to the original 49 second length, but blend frames from 50 down to 30 so that none are totally skipped. They’re just merged into neighboring frames in a sense.

When creating new project with 50fps and adding my special 50fps clip everything is fine.

Concerning shotcut 21.05.01 I don’t want to upgrade mine now in the middle in the project (I noticed many times that there is no backward compatibility and sometimes the filters from older shotcut imported to newer one works slightly different (thus frames look different).

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