Taking a small image (less pixels) and scaling it up (to an image with more pixels) requires adding more information to the image.
Your options for doing this depend on whether or not this information is available and how you plan to fill in this information (which can depend on where you got the image).
From the internet
If you found the image on the ...
Probably overkill, but DaVinci Resolve - Mac, Win & Nix - is freeware unless you're a pro video editor who needs hardware integretion.
That's literally one of the world's best video edit suites… for free. I honestly have no idea why it's not mentioned in that review, it's right up there with Final Cut Pro & Adobe Premier.
Otherwise, people tend to ...
I personally use ffmpeg using command like:
ffmpeg -i input_file.mp4 -c fixes_input_file.mp4
This help me recover from repeated error with source files in DaVinci Resolve
Also I use (depend of the video) command in this way:
ffmpeg -i input_file.mp4 -c copy fixes_input_file.mp4
What you seem to need is not a video "editor" per se, but a simpler tool for trimming and merging. A very important (in fact, crucial) feature of such tools is that they can usually do lossless editing without re-encoding the video.1 Apart from preserving the quality, it is orders of magnitude quicker, practically instant to save.
The one I use is ...
You can use Write-on Video. It is an intuitive timeline-based video editor. Can crop, cut merge videos. Kdenlive is the another software for video editing. It's free and open-source. It works in GNU/Linux, Windows and BSD.
these might help, but there's probably more.
Most likely very expensive options
Not as expensive options
Personally I would suggest the following combination:
Audacity for the sound editing
Python + Moviepy as a front end for:
FFMPEG which does the heavy lifting on the video processing.
ImageMagick for titles & captions
The other optional dependencies
GIMP for image editting
VLC for previews
The really good news with the above is the total price, ($0....
I personally use Adobe Premier Rush and I love it. I have used Final Cut Pro and Adobe Premier in the past but for the price they're not worth it for creating simple split-screen videos. Here is a Youtube video of how to actually make one:
It isn't free, but you can start by paying monthly for it on Adobe and ...
How about LosslessCut?
Shave gigabytes off video and audio files in seconds without loss of
Losslessly trim or cut out parts of video/audio
Lossless merge/concatenation of arbitrary files (identical codec parameters)
Lossless stream editing: Combine arbitrary tracks from multiple files
Losslessly extract all tracks from a file
Remux into any ...