Annoyance: People who chew food with their mouth open

I was taught at a young age table manners and etiquette. My dad had drummed it into me all of my life. So whenever I'm in the company of someone who 'smacks their lips', chews with their mouth open, or be a noisy eater really grates on my nerves. I just want to slap them. Okay, sometimes when I'm eating I put food in my mouth that's too big and have to chew a few times before being able to close my mouth; but I make a conscious effort to chew with my mouth shut. I just wish they did the same

This video on YouTube shows how it makes me feel:

Another thing that annoys me is people who chew gum with their gob open! Just stop it