@42piratas,
If you have local files, there’s no reason to bring Brave into the equation – Brave would be the “third layer” in this scenario.
If the files are local, open up VLC or whatever your preferred media player (w/casting capabilities) is and cast to your TV/device directly. There may be a way to funnel the connection through Brave via some extension or something but again, I’m not sure what the advantage of doing that is.