If there's one trait shared by all of our HD sources today, it's inconsistency. For the difference in terms of sharpness and, especially, MPEG noise can vary enormously from HD programme to HD programme within each platform we've covered.
However, for us the best results overall consistently come from the Sky platform. This is particularly true with Sky's own 'showpiece' stuff, like its sports coverage, high profile dramas, and top-line movies. This is presumably because Sky can manipulate the bit-rate with which it broadcasts HD material, upping the rate when it wants to showcase particular HD highlights.
At times, in fact - we're thinking in particular of memorable debut HD broadcasts of Zulu and The Italian Job, which Sky helped master into digital HD - Sky's broadcasts of films look superior to the Blu-ray versions! But on other occasions, usually with less popular material, HD sources can suffer clear blocking noise and softness, to an extent that can actually leave pictures looking only marginally better than standard def.
The good stuff is far more common than the rough stuff, though.
Next down the list for HD quality, we'd say, is actually the Freesat platform. For while it only has two HD channels, these do look as clean and clear as I've seen them anywhere else. In other words, Freesat appears to broadcast its two channels using whatever data width is apportioned to them by the BBC and ITV providers. It doesn't add any compression of its own.
That said, the quality of at least the BBC's HD channel has noticeably reduced on Freesat over the past 12 months, presumably on account of the BBC switching to a lower broadcast bandwidth (though the Beeb denies that this has affected picture quality). Some people believe the Beeb has done this so that its Freesat pictures will look more similar to those possible via the more bandwidth-constrained Freeview HD platform. But this is mere speculation, so let's move swiftly on.
The Virgin system is, in some ways, the most consistent HD performer. There are still obvious differences between different programmes and different channels, but they're less pronounced than they are on Sky's platform. However, part of this more consistent HD pattern finds Virgin's HD pictures looking slightly softer than those of its satellite-carried rivals.
Our weakest two HD performers are Freeview HD and BT Vision. Perhaps because it still has to work with relatively limited bandwidth, Freeview HD pictures look slightly softer and noisier than the best HD signals. And BT Vision's downloaded HD pictures tend to look a little gritty.
It really is great to find so many HD sources available now - especially as the UK's HD offering is far in advance of that found elsewhere in Europe. But inevitably, it's still a fact that if you really want to shift your whole TV lifestyle to HD, where you only watch standard def on rare occasions, you're going to have to pay for the privilege by going the Virgin or, best of all, Sky routes.
If you can't afford to pay for the hefty Sky and Virgin subscriptions, though, the Freeview HD platform really is shaping up to be a very likeable free alternative. Its three channels of free HD contain plenty of varied and solid quality HD content, delivered through existing or easily upgraded aerials to affordable receivers. The only catch right now is the service's limited coverage area, but that will be sorted over the next year or two.
Freesat doesn't have the coverage problems of Freeview, but by only carrying two channels of HD, it's starting to seem like a rather fussy option compared with the dish-free Freeview HD option.
BT Vision is the least attractive HD service. But to be fair, its on-demand services do offer something unique in catch-up TV terms, so it's perhaps not surprising that HD currently feels like something of an afterthought.