how can a convert a brawl video to a video on PC?
Unfortunately, you can't. Brawl videos aren't actual recordings of battles, just the commands you enter on the controller. Basically, it's just playing the match the exact same way you played it at the exact same timing.
I had a feeling...ever since I changed a character and the reply showed that I died within 5 seconds :>.>palm:
Yeah sorry about that. I heard you can record in game video with USB Gecko or something like that, but I can't confirm that since their site isn't working properly right now >_>