Stretching (change of aspect ratio, not cropping or scaling)

Hi team, I have a few 960x2160 videos with 4:9 aspect ratio I want to upscale to 3840x2160 16:9.

It appears that even the current beta only supports scaling to 400% on both axes (preserving the 4:9 aspect ratio), or cropping (it upscales to 3840x8640, but the custom parameters only put out a slim strip of that video if I enter 3840x2160 in the original undesirable 4:9 aspect ratio).

What I want to achieve is monodimensional upscaling x axis only (stretching 960 to 3840) while preserving and only cleaning up the y-pixels.

Is there a hidden way to achieve this?

Thank you kindly in advance!

When your video has a SAR or DAR flag (to correct for non-square pixels) VEAI will respect that. For example if you have a 720x480 video, it will display as 4:3 and when you process it at 100% resolution the output resolution will actually be lower at 640x480, but with square pixels.

In your case the 960x2160 video with the correct SAR or DAR flag applied should output to 3840x2160 when set to 100%. Whether it will be upscaled correctly and look good is another question though.