CNET también está disponible en español.

Ir a español

Don't show this again


Head of BBC HD says 'reducing bit rate has no impact on picture quality'

In an extraordinary interview with Points of View, the head of BBC HD says there's no evidence that reducing the bit rate has a negative impact on picture quality. Sadly, science disagrees

The BBC recently reduced the bit rate of BBC HD, leading to outraged complaints about the picture quality. The BBC has admitted that it has reduced the bit rate, but it also claims that its new, more efficient encoders make up the difference with increased efficiency. But in an interview with Points of View, Danielle Nagler, the head of BBC HD, said that there's "no evidence that reducing the bit rate has had an impact on picture quality". Which strikes us as absurd.

We agree that good encoders are very important, but they can't work magic. They can make very real data-rate reductions, and we're all for that. But what the BBC has been doing recently is reducing the bit rate to the point where even its new encoders can't produce the kind of picture that BBC HD viewers are used to, and expect.

We have our own theory about this, namely that the BBC is bringing the freesat BBC HD feed down to the level it will be on Freeview HD. Doing this will mean the corporation won't have to listen to people moaning about how one platform is better than the other, and it means it won't have to push out two different HD video streams.

As always, the commenters on the BBC Internet blog have done a lot of hard work to prove the image quality is greatly reduced. There are several A/B comparisons by a commenter called HD_fan428 and we think it's quite easy to spot the difference between the old encoder and the new one. The same user has made some specific illustrations, which show some of the very unpleasant picture degradation on certain images. Take a look at this screenshot, and you'll see nasty blocking effects and a very distinct lack of fine detail, as well as some solarisation artefacts.

It's our view that HD is, and always should be, a high-quality proposition. It's a premium service, and there's no point offering it unless you're going to treat it as such. HD channels need to use plenty of bandwidth to do HD well. We've said this before, and we'll say it again, but just because something has a resolution of 1,920x1,080 pixels, or 1,280x720 pixels, doesn't make it HD. We're not going to deny that encoder efficiency plays a big part, but it will only get you so far.

The BBC has now reduced its data rate to a touch below 10MBps, which is a significant drop, and makes it one of the lowest bit rates of the HD channels available in the UK. This is not what we expect from the nation's broadcaster, and if Sky can manage to produce good HD channels, why is the Beeb struggling so much?

Then, as if we weren't all annoyed enough by the bitrate debate, Points of View moved along to the BBC HD on-screen logo. Many complain about the digitally originated graphic that the BBC forces us to look at on BBC HD, but Nagler's ruling on the matter is one of the most arrogant things we've ever heard. In her own words, "I could take it off, but I don't think I'm going to."

Put simply, Nagler is saying that despite people strongly disliking its presence, she doesn't particularly care for their licence fee-paying opinions. We've always opposed on-screen logos, because they serve no purpose other than to make the BBC marketing department feel worthwhile. Those who don't care about DOGs wouldn't miss them if they went, and those who do care passionately want rid of them. So who loses if they go? No one. Well, apart from the guy in charge of the machine that generates it, anyway.