iphone videos

I downloaded videos from my iPhone to photos. The videos don't play in photos. I exported them and they came out as i4v format. Quicktime can open them, but clicking on "play" does not start to play; however, when I fast forward, they play (in 2x or more). I can see the total time indication at the end of the clip is a negative time, and when I fast forward the absolute amount goes from, e.g. -1.59 to 0.0. Normally, the duration would appear as a positive number, but I don't know how to change it.

The same thing happen when I convert the file to m4a or mov, so I don't think this is the i4v format.