[andymt]

all i can say is that if the broadcasters encode the channels themself then this might be useful-

on digital terrestrial, itv is also a weaker signal/and appears more pixelated in a low signal area.

this is because the network with itv on it also has many analogue channels on which take up more bandwidth, but, more channels are squeezed into low bandwidth to cmpensate this
there is no such problem with the bbc network,
however this is dtt, so it prob does not correlate to digital cable.