i see stackoverflow didn.t answer your question, yes you leave alot of signature. This isn't a solution (am still working on that) but a way out. I suggest you look at
tarantula:This gets all the movie meta data from IMDB then corelates it with that on
http://rottentomatoes.com, if by chance the movies is there on rottentomatoes, it download the trailer from there (rottentomatoes.com). I know this isn't what you are looking for.
Else, you could set out to write your own parser but you are gonna have to pour through
Downthemall code to see how they always manage to find video URIs.
@IFailStuff, he needs some code to put in his python script to download FLV files from IMDB. He insists he won't use any other software. Maybe just a learning process. If it was Youtube then Pafy would have done the Job.