Miranda warnings are required prior to in custody interrogation, not prior to arrest. The guy had no right to a Miranda warning.
I viewed the video yesterday. I don’t recall seeing the cop explaining to the man that he was making an arrest. I recall the cop telling him to put his hands behind his back. The cop appeared quite unreasonable. He did not want to show the guy where he broke the law. He did not warn the guy that if he did not sign then he would be taken into custody / arrested. I think the cop botched it pretty bad. But I am sure the judge will side with the cop since they always seem to no matter the circumstances. With a good enough attorney, I think the guy probably can sue the city / county / jurisdiction, and use the tape to sway the jury.