In what software can I perform a specific video editing technique and convert it to a web format?

Question

Video processing

Making a video background for a website
1) The website uses a full-screen section with a video playing in the background
2) The width of the viewport (and therefore the section) can vary from 768 to 1920 pixels.
3) There is a video of size 800x480
In order for the video background to always occupy the entire width of the section, I want to do the following editing:
1) Change the properties of the video file so that its dimensions are 2000x480
2) Divide the video itself into several pieces of the same duration and line them up by horizontal lines
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Please advise how to perform this video editing technique:
1) Change the width of the video "canvas" (from 800 to 2000 pixels)
2) Fill the resulting space with pieces from the same video
3) Convert the resulting video from avi to web formats webm and mp4
It is desirable that this can be done in a free online service.
Thank you for your help!

Answer 1

ffmpeg

Answer 2

And the second answer, no less classic - gstreamer.
Both tools solve this problem - you just need to select the options.