I read about SVT-AV1, and apparently, it's faster, but the quality is terrible. However, I checked available codecs in FFmpeg once again, and indeed, there are more to choose from (previously, I didn't expand the terminal window :P). I tried other encoders, and they are much faster (around few seconds). The whole idea of the program is "do it automatically," so I need to figure it out how to detect the most optimal encoder when the program starts. An update is coming soon.