If it's a produced film, you could also run into potential trademark issues with the characters and such. Some studios won't even allow you to show a produced film without permission, much less use it for personal projects.
(btw - transcribe is an odd way of saying what I think you're trying to say. Usually, a transcription means a word-for-word written record of the dialogue/script, not converting something into a short-form. And there are plenty of studios and prod. cos. that restrict public display of even written transcripts. That's why it's so hard to find many of them online, even for those with hearing impairments who might like a written version of what they watch.)