Capping the bet is also known as "Pressing" or "Past Posting". This is when a player increases
their bet after they already know they have a winning hand.
In the video, the guy on the right has a few chips in his hand as he reaches out to give the dealer a tip. This is before the dealer has gotten to his hand. As he is doing this, he knocks over his bet and adds a couple chips to the pile, then he finishes putting out the tip for the dealer.
If you look at his stack you can see that it is now higher than before.