BBC, ITV 'learned how to use HD bitrates'

Thursday, November 19 2009, 12:16 GMT

By Andrew Laughlin,

The Digital TV Group has said that broadcasters have "learned" about effectively managing bitrates for high definition channels ahead of the launch of Freeview HD.

The BBC was recently criticised for a 40% reduction in screen resolution for BBC HD on Freesat after it introduced new encoders in August. ITV HD also suffered a temporary reduction in screen resolution in September from 1440x1088 down to 960x1088 due to routine maintenance on an encoder.

Earlier in the week, the BBC confirmed a rollout timetable for Freeview HD, including the aim of 50% UK coverage for the service in time for the World Cup tournament in June next year.

However, existing HD screen resolution issues on Freesat have been widely criticised by viewers, leading to fears that the same problems could result on Freeview HD when the service launches.

In response, DTG director general Richard Lindsay-Davies claimed that broadcasters have "learned" from the issues on Freesat how to effectively manage bitrates for HD channels, especially in terms of the specific requirements for different types of content.

"If you've got fast moving, native HD content with lots of movement within the picture, then you need amazing bitrate to deliver that well. If you have something that is bordering on stills, then the bitrate is less important," he said.

"I think that broadcasters will start using a bigger array of technical tools available to them with DVB-T2 and MPEG-4, things like statistical multiplexing, to ensure that they share bandwidth around. But also, they will make some decisions on the importance of the programme and the kind of genre that it is."

Lindsay-Davies said that most of the time a high bitrate is not required, but broadcasters must be aware when a particular strain of programming needs a greater allocation.

They must also be mindful that if they have promised high definition distribution, they must "set aside adequate bitrate to do it justice", he added.

"I do think that they've learned a lot. A couple of the broadcasters have got away with murder on the terrestrial channels with very, very low bitrates, and the smaller broadcasters are not using very big bitrates at all," he said.

"But the BBC HD mux has been designed with appropriate capacity to manage those services very well and there are no plans to deviate from that at this stage."