I did see a film of part of a funeral service for a Union soldier in the films "Echos of the Blue & Gray" but it was a much later event as the film included sound. I assume that it was probably later than 1930.
Hadskey report states that Nathan A. Lott never mustered with the 7th so I have no idea how long his service to the regiment was. I believe the old veterans evidently considered him a fellow vet by their use of the flag at his funeral. There was a Nathan Lott who served in the 2nd Regiment, Mississippi Infantry (State Troops, Quinn's). I bet this is the same man but we need to research this more. Another man named Nathan W. Lott served in the 27th Regiment, Mississippi Infantry but I don't thin that is a match.
Maybe you and Mitch can work some magic and provide more details on this man.