ATV 3 white dots on TV screen, why?

Hi, so I just got my ATV 3 around 3 weeks back and have encountered the same problem since the first setup. I notice there are a lot of tiny white dots on my TV screen, sometimes it's extremely obvious sometimes it's just a tiny bit. The video settings are all set to Auto. I tried reducing the TV resolution from the auto setting 1080p 50hz to 1280 x 1024 60hz then the white dots disappear at once. I wonder what has caused this to happen? HDMI cable? TV? Internet connection? My TV supports full HD which is why I hope my ATV could provide video output of 1080p. Any geniu