In the last two weeks the picture quality has deteriorated on alot of channels particularly e4 .sky arts sky 1 alibi dave bbc and itv . It also effecrs programmes stored in my programmes from those channels effected. This is only on the tv as when i watch on devices its better . Is this a HDMI cable issue? Ive checked everything and done several reboots. If it is a cable issue can i but a replacement from anywhere or does ot need ro be a specific place? . Or could the fact my sony bravia tv is 6 years old and i need more up to date technology?