Video Grabbing Script

I have had a website designed. I now require the script which will allow users to paste video URLs and then convert them to a variety of different formats. eg. mp3, avi, flv etc. The video links will come from YouTube, GoogleVideo, Yahoo Video, MetaCafe, and Photobucket and the script will need to grab the video to convert just from the URL the user posts.

I do not require any of the user portal programming for the site, just the grab and converter script.