BBC hit by complaints about quality of HD broadcasts

 

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Posted on 17 Dec 2009 at 12:17

Viewers of the BBC's HD channel have been making complaints to the broadcaster about an apparent drop in quality over recent months. It seems their petitions have fallen on deaf ears as the BBC Trust - the corporation's governing body - referred the complaints to an executive who flatly denied there was a problem.

Back in August, the BBC changed the encoder hardware used to compress the video for transmission via Freesat and Sky. This change included a reduction in the bitrate - the amount of data transmitted per second - from around 16Mb/s to around 10Mb/s.

While the head of BBC HD, Danielle Nagler, said, "There's no evidence that reducing the bitrate has an impact on picture quality", there are a plenty of viewers that disagree with this. In fact, there are scores of angry posts on her blog, asking why nothing is being done to prevent BBC HD's quality from going down the pan. The BBC's claim is that the new encoders can produce the same quality at a lower bitrate.

There's some speculation that the BBC has plans to introduce a second HD channel, which might account for the reduction in bitrate in order to make room. However, others hypothesise that the decrease is more due to the fact that the channel couldn't be broadcast on Freeview HD at the higher bitrate. Interestingly, viewers watching BBC HD on Virgin's TV service aren't affected by the change since it uses the older bitrate of around 18Mb/s.

We've not yet had the opportunity to compare BBC HD on Freesat HD and Freeview HD due to the lack of hardware for the latter, but it's important to note that the quality of the image depends on the hardware being used to view it. Both set-top boxes and HD TVs process the incoming image to smooth and sharpen it, and this can affect the final quality. Arguably a more important factor is the size of the TV you're watching, and how far away you're sitting. Any changes in sharpness and compression will be more easily noticeable if you're sitting six feet from a 50in set, than if you're sat at the same distance from a 32in TV.

Nagler has also been quick to point out that production techniques also affect quality, stating, "HD from the BBC does deliver in a range of styles - and that is not always the bright, crisp look which for some is synonymous with HD. There are a number of programmes that we make where that kind of appearance would feel very odd indeed. Different types of cameras used in different ways, with different techniques in post production, will deliver different outcomes." We're not convinced about this, but we'll keep you updated with any developments to this story.

Author: Jim Martin