I'm rendering videos I recorded using Zoom for my classes, mostly a slide show and my voice.
A 30- to 40-minute video takes up about 60MB as recorded by Zoom in MP4, at 2560x1440.
I then add a simple title in the beginning, cut a few seconds before I start sharing the slides window, and add a couple of 150-pixel logos on the corners, and proceed to render to a local file and to YouTube.
Local rendering takes about 2 hours of rendering, plus another 2 hours to export to YouTube. Both the original files and the result are placed in a SSD drive, the machine is a 2019 iMac Pro with 64 GB of RAM. Rush's thread is running at 114%, only about 8GB of the RAM are taken by Rush's process, there are loads of free disk space in the SSD. The final video is rendered with medium quality, mono sound, 720p, and still ends up with 5 times the original mp4 file size.
What am I missing? I produced several videos a couple of months ago, with much faster rendering.