Huffman compression already in place on Freesat
November 17, 2009
EXCLUSIVE: Freesat has used Huffman compression – the subject of an extended Ofcom consultation over its introduction on Freeview HD – since launch, Broadband TV News can reveal.
Huffman, incorrectly labelled in some quarters as encryption, is not directly involved in content management. However, the BBC is looking to license manufacturers that want access to the Huffman tables to build in the HD content management technologies needed by broadcasters to maximise the range of content available on their HD channels.
“Huffman compression has been there since day one, as part of the content management, but it doesn’t have the ability to change on a programme by programme basis,” Graham Plumb, acting controller, distribution, BBC Operations Group told Broadband TV News.
In the case of Freesat, Huffman ensures that only approved manufacturers gain access to the SI (Service Information), differentiating them from standard free-to-air receivers in the market. Huffman was indirectly responsible for the closure of Sat4Free, which attempted a Freesat-like service in the Irish Republic. If Huffman is used on Freeview it could potentially restrict the number of manufacturers in the market, but this is unlikely given that the majority are members of the Digital TV Group, with which the BBC has been in active discussions for many months.
If the BBC is successful in persuading Ofcom to allow Huffman to be used on Freeview the corporation, which operates the HD multiplex on behalf of the PSBs (public service broadcasters), would be able to set content management states using DVB standardised signalling flags. For the majority of programmes it is likely that viewers would be able to record broadcast content as they pleased, but with an acquired series such as the sci-fi drama Heroes, a viewer might only be permitted to make one recording to an external device. Use of a PVR such as the proposed Freeview+ HD receivers would be unaffected and the viewer would always be able to archive one copy to a device such as a Blu-ray recorder.
“There is not a large number of programmes that the studios have concerns about, though it is conceivable that a message might come up to explain that a programme is not available on this platform,” said Plumb, illustrating a worst case scenario.
Arguably the key difference between the terrestrial and satellite platforms is that the PSBs are required to make terrestrial transmissions, but this is not the case with satellite.