I just recently "fixed" this issue in my house. There is a single Cable TV feed that comes into your property, which
is then split up into multiple wires that go into different rooms in your house (living room, bedrooms, kitchens, etc.) The more branches this cable gets split into, the worst the signal becomes. I had 6 branches from my splitter, we had major issues with color smears and grainy/pixelated pictures. At first I thought my TV was going bad, but I had 3 different TVs that all have the same issues ... Anyway, I did some research and conclude that I need a Cable TV amplifier. Went on Ebay, bought a good one and voila!, everything becomes crystal clear again. I don't know if you have this same problem, but if you want to pursue this path, I can tell you in details what I did ...