How to upscale video to better quality

I would like to upscale a video from HD to 4K in Blender. How do I do this?

theres a scale node in the compositor. or you can increase the render dimensions. make sure the percent slider is at 100.

Unfortunately … “you can never move from noise to less-noisy.

You can never move from a sow’s ear to a silk purse.
You can never move from what is there to what is not there.

Perhaps the two targets are close enough that you can successfully “fake it” from one to the other – goody for you – but the general principle still holds. You can calculate your way to less quality, but never to more.

Shorter version - making it bigger will reduce effective quality. This will be especially evident when doing this to create 4k content from lower quality sources. There’s a reason why some are skipping recording in 4k and instead jumping to 8k and downscaling.

You always need to do that! Your “original data source” must always be at a resolution that is equal-to or greater-than the highest resolution that you will ever need to produce from it, so that each and every step always goes down.

Also, if you need to produce several outputs at different levels of resolution, each of these conversions should source from the same, highest-resolution source. (Specifically: do not down-sample from a down-sample output … noise will accumulate very rapidly.

Yes, there was a reason why film photographers used 4"x5" or even larger pieces of sheet film in those “old-timey” cameras, and why magazines who prized themselves on the quality of their printed images required their photographers to use such equipment for every image that they submitted.