What download speed do you have. I find that sometimes I get buffering on busy sports channels, like when there's a important game and other days the same channel has no problems.Well a lot depends on the type of IPTV Box, but more critical is the Download Speed of your Internet Provider.
Remember that the best quality will be a hardwired connection from your Internet Modem and directly to your IPTV Box or TV.
My IPTV box picture quality is perfect, with a rare freezing from a a very remote foreign TV Channel. Canadian and USA Channels are perfect quality.