I am trying to do a composition of two videos, one being full-screen while the second one appears as a small window in one corner, as in the following example: Example of current composition

Ideally, I would like to round the corners of the video at the corner and add some border to it:

Picture-in-picture with rounded corners and border

I couldn't find information about how to achieve this result. I tryied to create a mask by VFX->Masking but I only managed to create a rounded rectangle by combining rectangles and circles, but this solution makes it hard to adjust the settings.

If rounding corners has no simple solution, it would fi fine just to add a border to the video.

Picture in picture with border only

Any help would be greatly appreciated!

  • $\begingroup$ You might try something involving blurring a mask and then doing a greater than comparison on it. $\endgroup$
    – TheLabCat
    Dec 16, 2022 at 15:23
  • $\begingroup$ You could mix the 2 videos in the Compositor with a mask as factor? $\endgroup$
    – moonboots
    Dec 16, 2022 at 19:27

1 Answer 1


version Compositor

TheLabCat's comment in images :) just ... I don't think VSE can handle this blur task, so ... version in compositor.

enter image description here enter image description here Originally I used Math node > Less than 0.5, but edge was jagged (without antialiasing) so I used ColorRamp node instead.

version Sequencer

For VSE you would have to use Mask (in a current version there is not an one click solution like in other apps, but on other hand with this system you have open a gate to endless and much more complex and animated masks.

It will be hard to create round corner in native blender's Mask system with rounded corners (seen under Paint Editor).
Would be probably more easier to create a "mask" object in 3Dviewport (or use bw image imported as a strip).

Here is example with mask from Scene ...
You already have one scene with VSE setup. Create another Scene in the same file and in 3Dviewport set Camera to Orthographic, Add a Plane at location you want to see Small Screen through Camera, add Solidify+Bevel modifiers, set white material and black world ...

enter image description here Left camera is the mask for SmallScreen, right camera with Plane is duplicated + one more Solidify modifier. It will works like a stroke thickness for Colour strip :)

So you should see something like this ...

enter image description here

In your VSE scene add two Scene strips (containing your masks) and under properties choose corresponding Camera object. Strips can be placed whenever you want (or hide them). We need them just for strip modifiers.

For Small Screen add Mask Modifier > Strip and choose Scene strip with mask done at the first camera. For a stroke add Color strip and ad Mask modifier > Strip > Scene with camera two ...

enter image description here enter image description here

File contains both version ...

To be more flexible you can create a rounded mask for entire screen, and under VSE apply mask to "small" screen at size of full screen, group strips and transform (scale, translate) whole group (image with stroke).


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