This issue has been discussed a couple of times and mostly vlc was the recommendation for pre-Sierra. However, on my Macbook Pro Retina (Sierra) vlc gives a poor result when watching a DVD through the USB SuperDrive. The mac dvd-Player is a bit better, but far from good, and is not an option since I cannot take screenshots.
Has, in the meantime, a player appeared that could be recommended?
Has, in the meantime, a player appeared that could be recommended?