America's cable operators are preparing to roll out a new series of set top boxes designed to support a raft of new high definition channels broadcast using MPEG-4 compression.

HBO, which plans to offer all 26 of its HBO and Cinemax-branded channels in high definition by the middle of next year, announced today that it is switching from Motorola's DigiCipher MPEG-2 encoders to equipment that will support both MPEG-2 and MPEG-4/AVC. However, the MPEG-2 capability will only be used to transmit HBO HD and Cinemax HD; all other feeds will be provided to both satellite and cable operators in MPEG-4 because of the newer standard's more efficient and cost-effective compression. Those providers will need to either pass through the MPEG-4 broadcast directly to set top boxes that support it or invest in transcoding equipment; DirecTV is already rolling out MPEG-4 HD boxes, and several cable operators, who are keen to switch to MPEG-4 to make more efficient use of available bandwidth, have put in orders for MPEG-4 capable STBs.

The decision by HBO - an important premium revenue provider for cablecos - to offer an all-HD package has helped speed along the adoption of MPEG-4. However, it is by no means the only major US broadcaster to announce big HD plans: Turner Broadcasting, which already operates a TNT HD simulcast, plans to offer TBS and CNN in high definition in short order. The Weather Channel is in the process of converting to HD, and is even planning to rollout a new series of local forecast-providing computers to HD-capable cable headends to provide a complete high definition channel.