Since the switch from MPEG2 to MPEG4 on alot of channels I have noticed a very sharp decrease in picture quality, is Virgin Media using a MPEG4 bitrate thats TOO low? some channels look god damn awful which didn't before?
Have you tried these channels on a screen at least 55"? They are terrible, only watchable if things are still but as soon as there is any movement it's like Lego Vision, HD channels look great, but SD channels since the change from MPEG2 to MPEG4 is awful, I don't receive any pixelation and my broadband is running at full speed, my house is newly wired and had numerous engineers say my signal is fine.
Also my best friend also has the same issue on her TV as we were talking about how bad it is these days.
P.S. The signal strength in the Diagnostics screen shows the signal strength to be between 99% and 100%
There is an issue in that whilst MPEG-2 works well in compressing 720x576, it isn't quite the same with MPEG-4. In fact, my suspicion is that the number of horizontal lines is reduced so that we've got something like 704x576 which leads to bigger images which are cropped, leading to a reduction of about 2.2%. The only things I can suggest are disabling screen overscan (which you should do anyway but is often enabled by default) and watching the HD channels if simulcast with SD.