Undoing nonlinear horizontal stretching?

I have some legacy 4:3 material that has been vandalised by horizontal stretching to make it 16:9.

(Something that should be made a capital offence, requiring a custodial sentence, but I digress…)

The problem is the stretching is nonlinear and appears to increase the further from the vertical centreline. It might be x-squared, or parabolic, or hyperbolic, or who knows what, but I’d like to “un-vandalise” these clips and restore the source material to its original and undistorted correct aspect ratio.

Do anyone know of any tools in DVR that could assist in such a process? It might require a degree of trial and error, since I don’t know what the underlying stretching algorithm was, so cannot calculate the exact inverse to undo it.

Thanks.

mmm...

you can try in fusion with the warp tool, make a grid with about 5 vertical zones and carefully by trial and error see if you can make the circle square, once you find one, you find all of them.

mmm...

you can try in fusion with the warp tool, make a grid with about 5 vertical zones and carefully by trial and error see if you can make the circle square, once you find one, you find all of them.

OK, that’s an idea.

I do have low-res non-distorted samples of some the original video, so I can use that to calibrate. I’m hoping that whatever nonlinear warp they did apply was consistent to all clips.

I'd make a 4:3 timeline and put all the vandalized 16:9 clips in there.
Go to timeline settings -> mismatched resolution -> stretch frame to all corners.
Like Walter said, you might need to use the warp effect afterwards.
I'd put the low-res non-distorted samples above the vandalized clips, put like 20 opacity, and try to match the clips. I do hope that the warp is indeed consistent to all clips..

Don't use opacity, use difference. It's easier

(Something that should be made a capital offence, requiring a custodial sentence)

Agreed. Along with jump cuts, blanking fill, and animated captions. All things that ruin a good video and make it unwatchable.

Thanks all for your suggestions. I’ll have a crack at restoring this video and report back!

you can try in fusion with the warp tool, make a grid with about 5 vertical zones and carefully by trial and error see if you can make the circle square, once you find one, you find all of them.

OK I can report back this can do exactly what I want!! So thank you very much for this pointer.

For others who ever need to do something like this:

1. Reduce the Y grid size to 1 so that there are only vertical grid lines in the Warp tool (in this case, I do not want to distort anything vertically)
2. Change the X grid size to whatever you want (I needed 12 to 16 vertical lines to do an accurate reverse distortion)
3. Ensure that "Show Key Points" in the toolbar is active, that the viewer is showing "Destination" not "Source", and the Magnet Type is "selected" so that only the selected Key Points in the grid are moved,
4. To move an entire vertical line in the grid left or right, and not just one end of it, select the Key Point at the top of the line, and shift-select the Key Point at the bottom of the line, so that both will move together.
5. Before moving either selected Key Point, hover your mouse over one of the selected Key Points so that it turns white, then hold down the Shift key to constrain the movement of the Key Points. Click and hold the mouse button down while dragging the Key Point (which should move the entire vertical line) to where you want. You need to be a little careful that the first mouse movement is horizontal not vertical, otherwise the constraint won't be horizontal.
6. Once done, click any other Key Point to deselect the two selected Key Points and repeat.

It doesn't seem possible to numerically control the position of the Key Points. Only visual, on-screen dragging.

Or maybe a macro could do it... a job for another day.

To move an entire vertical line in the grid left or right, and not just one end of it, select the Key Point at the top of the line, and shift-select the Key Point at the bottom of the line, so that both will move together.

You can also draw a bounding box by click-dragging the mouse - all of the points within the box will be selected.

It doesn't seem possible to numerically control the position of the Key Points. Only visual, on-screen dragging.

You can move selected points using the keyboard arrow keys. Using Shift+Arrow moves them by 10X as much as the arrow keys alone. So if you're looking to reproduce a particular offset you can count how many arrow key pushes it takes and then repeat that with whatever other points you need to match with. A little kludgy perhaps, but more accurate than using the mouse.

Something that should be made a capital offence, requiring a custodial sentence

Hehe... 'Elastic Aspect' was one of my more popular plugins, back in the day, designed specifically for non-linear vandalisation of 4:3 footage. You're welcome.

You can move selected points using the keyboard arrow keys. Using Shift+Arrow moves them by 10X as much as the arrow keys alone. So if you're looking to reproduce a particular offset you can count how many arrow key pushes it takes and then repeat that with whatever other points you need to match with. A little kludgy perhaps, but more accurate than using the mouse.

Thanks for that, that is very helpful to know!

Something that should be made a capital offence, requiring a custodial sentence

Hehe... 'Elastic Aspect' was one of my more popular plugins, back in the day, designed specifically for non-linear vandalisation of 4:3 footage. You're welcome.

Just because you can do something doesn’t mean you should…

There were even some TVs offering that as an option…

There were even some TVs offering that as an option…

My DVD player has it as an option!

Why anyone found pillarboxing so offensive that it needed to be “solved” with visual vandalism instead I’ll never understand…

There were even some TVs offering that as an option…

Why anyone found pillarboxing so offensive that it needed to be “solved” with visual vandalism instead I’ll never understand…

Same reason that many find 9:16 video on a 16:9 display to be an abomination...