Your teacher may "dictate" a dialogue, a monologue or a passage from a book during a class. You would then "write down the dialogue from a video" or "transcribe a dialogue from a video".

"To dictate" -> someone reads aloud for the purpose of someone else to write it down. e.g. "I dictated a letter to my secretary." (... and virtually nobody does this anymore in the age of computers!) "To transcribe" -> I transcribed the audio from the tape/video -> I wrote down exactly what I heard on the tape/video.