That's why you'll see those folks on video asking;
"Am I being detained?"
"Am I free to leave (go)?" (This interrogation, not necessarily the festival on public property.)
They'll often repeat these phrases because being detained is a legal stance. You'll see in some of those video's the police don't like folks questioning their authority. Yet the police know that there are limits to this authority. If you're not being detained then they aren't about to arrest you. Thus they are limited in what they can legally do. So, by asking 'Am I free to leave?' your ending their interrogation without being insulting.
There have been other video's done, by lawyers, suggesting this exact response. More they were done for folks that may have had illegal drugs in the car and not submitting to an illegal search and seizure.
But that advice also pertains to any time police start getting past just a conversation and start interrogating you. You can't be insulting, but cooperation in getting yourself arrested by giving them to much information is against the 5A.
That's when you'll often see the cop asking if they are a lawyer, because they know they've crossed the line yet still can't stop themselves. Hoping you don't know or aren't willing to stand up for your rights.
That's they game they (the police) play. And some of the best free legal advice you can get. They are hoping you'll just give up and let them abuse their authority, with your consent. They need that consent and they know it. Those phrases given at the top are to stop the runaround the Constitution and the laws. If they answer that your not being detained and are free to go the interrogation is over. And until you get an answer like that you can't just walk away.
Do it wrong and you could find yourself proned out eating concrete.
"The human race divides politically into those who want people to be controlled and those who have no such desire." - Robert A. Heinlein
What a shame that we have the two major political parties that believe the former.