scouser

Whats the best command line tool (osx/nix... maybe could load up windows if its decent enough cl tool) to mass edit videos?

I want to do these things -

add preroll/postroll
convert to mp4/avi/wmv
convert size/bitrate down
add watermark (image or text)
sometimes rotate or flip images

i know i can do some in ffmpeg (not sure if can do them all). anyone got any recommendations?

also how do you normally get screen grabs? at the moment im just basically print screening vlc and pasting to photoshop. is there an easier way (maybe a (non command line) app just for extracting captures from vids that shows many screenshots (like on a timeline)) or something???

thanks