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Audio Formats Approved For Future HD Video Discs

Consumers won’t have to replace their current 5.1-channel home theater receivers or preamp/processors if they want to enjoy discrete multichannel surround sound when they’re watching movies on future high-definition (HD) video discs.

Consumers might have to invest in a new receiver or preamp/processor, however, if they want to hear the enhancements promised by many of the surround-sound formats approved for optional use in future HD disc players.

That’s the word from the DVD Forum and the Blu-ray Disc Association, which have approved mandatory and optional audio formats for their competing disc standards. The standards, respectively, are high-definition DVD (HD DVD) and Blu-ray Disc (BD).

For their respective disc standards, each group approved multiple mandatory audio formats that each player must support. At least one of those formats must be included on prerecorded discs, but the choice of formats is up to individual movie studios.

For compatibility with the installed base of discrete multichannel surround-sound receivers and preamp/processors, the two groups mandated Dolby Digital 5.1 and DTS 5.1 as mandatory player formats. As a result, HD discs’ soundtracks will be playable in discrete 5.1-channel surround through the installed base of 5.1-channel, 6.1-channel and 7.1-channel home-theater surround-sound systems.

The Dolby Digital and DTS 5.1 mandates also ensure the ability of an HD player to play the 5.1-channel soundtracks of a DVD disc if — as expected — marketers sell HD players that play current-generation DVD discs.

Some optional 6.1-channel formats will also be playable through current-generation receivers and preamp/processors. The HD DVD and BD specs, for example, provide for optional 6.1-channel DTS++ formats compatible with existing 6.1-channel DTS ES Discrete and Matrix decoders. These signals can be sent to the receivers and preamp/processors via traditional 1.5Mbps digital SP/DIF connection.

HD DVD players also allow for an optional Dolby Digital Plus 6.1 format that’s compatible with Dolby Digital EX decoders.

For both disc types, however, other optional high-bit-rate 6.1-channel and 7.1-channel formats will require the purchase of a new multichannel decoder, which could be built into future receivers. These receivers would need a wide-band input to import the high bit-rate audio signal in digital form. Although neither group has established a maximum audio bit rate, DTS said it expects both disc types to support audio bit rates out to around 18Mbps.

HDMI inputs and outputs have the bandwidth to pass through such a wide-band signal, but it isn’t certain whether the HDMI spec will have to be amended to accommodate some of the standard and optional audio formats, DTS said. Neither the Blu-ray Group nor the DVD Forum have announced their approval of a specific type of digital output.

For some consumers, however, it might not be necessary to replace their current receiver at all — if they buy an HD disc player with built-in high bit-rate decoder and 6.1-channel or 7.1-channel analog outputs. The outputs could be connected to receivers with 6.1-channel or 7.1-channel analog inputs.

Although some of the new audio formats are expandable to more than 7.1 (eight) channels, marketers don’t expect consumer-use players or discs to include such a capability. In any case, if future HD soundtracks were to contain more than 7.1 channels, first-generation decoders would be able to manage the signal, DTS said.

For details on the groups’ decisions,