Q: Using Speech/Dictation feature to transcribe a saved audio file?

Is it possible to use the Dictation & Speech application on my MacBook Pro (El Capitan) to convert an audio recording (I have saved to my computer) to text?

Can I set it up as if I am going to speak but just let the audio recording run & have the application transcribe to text?

I know it's probably a long shot but thought I would ask before I spend the time transcribing an audio conversation of about 30-45 min. :-)