There sure is confusion between .mp4 and .m4v because people think they are different when they are not. These 2 suffixes can be applied to MPEG-4 video files that are exactly the same in every way. Double-click the file and there'll be different behavior: .mp4 opens in QuickTime Player whereas .m4v opens in iTunes by default. But drag-and-drop onto either application will open either file type. I hoped that helped you out man