[rdhw]

There are many possible factors affecting picture quality:

1. if it's just some channels affected, then it's not your V+ box at fault.

2. different channels are transmitted on different multiplexes on different frequencies on the cable. Sub-standard signal levels might affect some frequencies more than others. This needs an engineer visit to check signal levels across the whole cable spectrum.

3. some channels are transmitted at lower bit-rates, and hence greater compression, than others. This will lead to greater perceived pixellation on movement. The "1970/80s repeats" channels are all pretty low bit-rate, while the big five terrestrial channels are all of higher quality. BBC News is of lower quality than BBC1 or BBC2, and this is very evident in MPEG artifacts around the graphics text.

4. Connection via HDMI, with its higher detail quality, can reveal more clearly poor picture quality in the original digital signal, where connection via SCART, with a redundant analogue conversion, might have smoothed over the rough edges somewhat.

5. it is unlikely that the VM picture quality is better or worse in principle than the Sky picture quality, as the VM digital feed for many channels comes from Sky. There might of course be individual Sky customers with poor satellite reception, and inidvidual VM customers with poor cable reception, but the picture quality from good reception on either system should be near indistinguishable.

6. the video signal processing undertaken by some consumer TVs can be counter-productive. For instance, I have found it better, on a Pioneer plasma screen, to disable all noise reduction and other video processing, such as PureCinema or whatever they call it.