Using online converters sucks dick, what free program do I use to convert MP4 to WEBM? Premiere Pro (which isn't free, but I have) doesn't support the format, VLC only gives me gibberish (converted video are extremely long despite only playing for as long as the originals, 4chan doesn't accept them) and the single stackexchange post that acknowledges this problem just says to use Avanti/FFmpeg. Problem is that Avanti says it's missing FFmpeg codec files, despite me downloading the lastest versions of both. So I can't get that to work either.

Someone show me the light.