Although a lot of opera DVD releases these days seem to be captured livestreams, I'm wondering in general about how operas are filmed for video release (especially how they used to do it before livestream productions). If you attended a performance that was being filmed, did they tell the audience? Give any special instructions to the audience? Do any re-takes? etc etc

Also, if you attended the filming of a performance that was later released on video, how well did you think it captured the actual performance?