https://archive.nyafuu.org/wsr/thread/951587/#951966tldr - the inefficient but short one-liner i'd suggest is:
ffmpeg -i input.webm -c:v libvpx -vf "scale=iw:ih" -crf 10 -qmin 0 -qmax 55 -an output.webm
replace iw and ih with your desired width and height
otherwise, the only other thing to change is the qmax value if you want a larger filesize
you ideally keep changing it until you're just under 3mb
full guides here:
https://trac.ffmpeg.org/wiki/Encode/VP8https://trac.ffmpeg.org/wiki/Encode/VP9although the 4chan only accepts vp8, the vp9 guide has a lot of applicable things to apply to your vp8 encoding as well
