The BBC Trust has given its full backing to the launch of a full-time HD TV channel and limited content may even appear on Freeview "almost immediately" thanks to the removal of other services.

The current BBC HD service is only a trial, due to run until later this year. A so-called Public Value Test (PVT) was needed to establish whether it was worth licence payers' money. The channel would pull channels from across the BBC's stations.

The Trust concluded a new channel will be of "high public value", adding it would make little impact on the market. Other new BBC services such as the iPlayer download service have to pass the same test.

For satellite and cable the proposal is for a nine-hour service broadcasting from 3pm to midnight. Some flexibility will extend beyond this to allow coverage of significant live sport or other events such as Wimbledon or a football World Cup.

HD to reach Freeview?

For Freeview, two options are proposed. The first would take place after the digital switchover with a full nine-hour service as described above. People would have to buy an extra set top box and would be reliant on extra spectrum becoming available. The Trust is determined to consult people on this, asking: "Would people prefer the BBC to launch the service as soon as possible, even if that meant people having to buy two set-top boxes in order to receive the service within a very short period of time?"

The second proposal is a shorter term solution with a four-hour scheduled broadcasting overnight between 2pm and 6pm. That's because there is no capacity for HD services on Freeview pre-switchover but it could still be of use for PVR owners. The BBC would need to take down BBC Parliament, BBC Four and three BBCi streams between the hours of 2pm and 6pm to create capacity for the overnight schedule.

However, the Trust makes it clear that "this action would be intended as an interim measure until spectrum capacity allows for the introduction of a nine-hour service".

Rearranging spectrum

The Trust says it "believes that an HD channel should be provided on Freeview as soon as possible and early next year [it] will review options for delivery on Freeview in the light of what might be technically possible following Ofcom's proposals for rearranging spectrum."

Ofcom will make the decision on the allocation of bandwidth post-switchover - it has been suggested Ofcom may sell off the bandwith rather than provide more space for Freeview HD channels.

However, as Alex Lane from our sister magazine What Sateillite and Digital TV comments, "it's likely that the Trustees will also follow recommendations not to launch an HD service on Freeview until a new generation of compression and broadcast technology is ready, which won't be until 2009 at the earliest."

The Trust says it will now launch a public consultation into its conclusions, which will run until 23 October. Other thoughts were also proffered by the Trust, including warnings over HD content being offered for download due to bandwidth considerations, as well as the consideration of IPTV. You can read more about them in the Trust's conclusions.

The BBC HD trial started last year with showings of Planet Earth and Bleak House. Football games have also been shown live in the format on the channel in simulcasts with BBC One.