Split Screen "Mirror" project -- how to adjust positions 'within' a position?

I would search for this question however I couldn’t even figure out a way to phrase it properly to even begin a proper search. I struggled to even phrase this topic title. I’ll try my best to explain what I’m trying to achieve here:

I started my “Mirror” project with much success.

  • 640 x 480 25 fps source
  • Use filter Crop: Source total of 320 (half) from left/right
  • Use filter Size, Position, & Rotate Horizontal fit - left
  • Copy/Paste whole clip to Video Track 2 (V2)
  • Select V2 clip
  • Select Size, Position, & Rotate and change Horizontal fit to - right
  • Apply Mirror filter

Everything looks as I want it to. The horizontal total of the video is 640 and 320 of the cropped video is on the left, and the mirror of this video is the 320 on the right. Now here is where my problem and question begins:

I want to use Keyframes to adjust the position at many separate parts of the video, however, I need the mirrored tracks to never break the horizontal positional divide in the middle (the mirror divide). Considering Keyframes can only be used with Size, Position, & Rotate, the Crop filter will not be useful with this project as I will need the full 640x480 video to ‘play’ with its positions, within a 320x480 positional ‘frame’ on the left half of the video (of which I will mirror to the right half).

Essentially, I need:

  • V1 clip (left) (640 x 480) must only be visible 0-320 x 480 (left half)
  • V1 must be able to position freely with never being ‘visible’ horizontally at 321-640
  • V2 clip (right) (640 x 480) must only be visible 321-640 x 480 (right half)
  • V2 must position freely, never being ‘visible’ at 0-320 horizontal of the video

I’m am clueless how to achieve these positions “within” a position and I still feel like I’m not phrasing this correct.


  • How do I dedicate V1 track visibility position to left half of the project and V2 to the right half?
  • How to adjust the positions of the tracks within there dedicated left/ right video positions?

Any input is appreciated on this! I’d really like to figure this out so if my post is confusing, please don’t hesitate to let me know and I’ll happily try to clarify.

If I understand your objective correctly (that’s a big if, but I’m confident) then crop: source isn’t really what you want to use at the start.

In your case, you DO want crop, but crop rectangle - applied as a filter - after the Size, Position, Rotate (SPR) filter. The easiest way is going to be to import your video to V1, add the SPR and the crop rectangle (in that order), then do your SPR keyframing, moving it around as necessary. Once you are happy with your work, only then copy that to V2 and apply the mirror filter and voila!

Here is an example created exactly as I described above. Just unzip the mlt and the video to the same folder, then open in Shotcut to see the how it works (there are keyframes on the SPR moving the video back and forth).

There might be another way to do this, but in the meantime this works and isn’t difficult to implement (assuming I did understand you correctly!).

Mirror.zip (1.2 MB)



So is this what you wanted, or did I misunderstand?

Yes, it worked like a charm. And, you have made a best friend for life. I read your post late Thursday night, went to bed enthusiastic about trying it the next day. I was hopeful when I first read your post and then I was ecstatic when I saw your video example. I was literally so busy playing with it all day yesterday that I forgot to respond.

It took me about 10 minutes to figure out to engage “Transparent” on the Crop: Rectangle filter. I was going back and forth between your project example and my project, and finally realized your project had the Transparency engaged.

In fact, “Transparency” was a word that completely escaped me when attempting to phrase this whole question. I’m half way decent with image editing so I don’t know why, it’s a common concept.

This whole mirror, positional freedom idea is super simple idea now that you’ve shown how to do it:

  • Size, Position, & Rotate
  • Crop: Rectangle cut half from the horizontal size (320), then engage Transparent
  • Play with the Position and Keyframes
  • Copy/ Paste V1 to V2
  • Select V2, add Mirror filter

My computer is kind of old, bit laggy and there is no lag at all with playback, either.

I sincerely appreciate you helping clear this up. I’m about half way through the 8 minute long video project right now. I will post the video here when finished. I feel like this “Mirror” idea is definitely not a novel concept at all and it looks like something out of the 60’s or 70s, but, it feels novel to me and I am having a blast playing with it.

I am eternally thankful for you taking the time make that example and .MLT. I was literally about to give up and scrap the project if nobody responded. Infinite appreciation for the consideration and for posting that!


All good mate, that’s what the forum is all about (and in my limited experience this is one of the better support forums, where someone will usually always come to the rescue).

Glad to be of service. Good luck with the rest of your project!


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