Export video based on audio file length?

I would like to export an audio visualization, which runs from the start of the audio file to the end of the audio file. Is there a technique for telling the export to simply stop when it reaches the end of the audio file? Or do I have to figure out/already know how many milliseconds long the file is and set the timeline by hand?

On that note, is there a way to determine the number of milliseconds long an “audiofilein” file is within the app?

Place an Info CHOP and point it to you Audio File In CHOP.
Now the INFO CHOP will show lots of useful information in its channels about your audio playback, the one you want is the channel fraction. With an Chop Execute DAT you can make it perform an action when that has reached 1, so for instance use that to control a Movie File Out TOP to render out your work.
example attached, it will print to Textport when you audio file is done

base_audio_playback_info.tox (854 Bytes)