Record video with internal sound

Hi there!

I used to use ofVideoGrabber to record audio & video together in the same file. That works very well and is so simple!
I’m using a C920 as cam and mic, but for this project the ambience sound is so high that makes the audio output terrible.

I’m controlling the audio using some bottles and arduino, so the “gift” for each one is a video with the remix of sound and projection.

Can I grab the audio output from Isadora as input and record a video using my C920?

If yes, is it easy to sync video and audio?
Thks in advance!

EDIT:
I need also output the audio to the sound speakers.