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Audio Formats Approved For Future HD Video Discs

10/08/2004 10:14:00 AM Eastern

New York— 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 standards. The standards, respectively, are High-Definition DVD (HD DVD) and Blu-ray Disc (BD).

For their respective 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-, 6.1- 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 formats, delivering 6.1 and 7.1channels or more, will require the purchase of a new multi-channel 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 standards will support audio bit-rates out to around 18Mbps for select high-bit-rate formats.

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 has 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- or 7.1-channel analog outputs. The outputs could be connected to receivers with 6.1- or 7.1-channel analog inputs.

Although some of the new audio formats are expandable to more than 7.1 (or 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.

Here’s what the groups decided:

HD DVD MANDATORY FORMATS

The DVD Forum specified three formats that HD DVD players must support: Dolby Digital Plus, two-channel lossless MLP (Meridian Lossless Packing) and DTS ++ Lossy.

Dolby Digital Plus soundtracks can contain 5.1 or more discrete channels at data rates up to 3Mbps. Soundtracks encoded in 6.1 or more than 6.1 channels will contain a 5.1-channel signal that’s compatible with existing Dolby Digital 5.1 and matrixed 6.1-channel Dolby Digital EX decoders. The players’ digital SP/DIF output will spit out the 5.1 signal at a data rate up to 640kbps, exceeding the 448kbps data rate of Dolby Digital soundtracks on current DVDs, Dolby Labs said.

Dolby Digital decoders in current A/V receivers are already equipped to decode 640kbps Dolby Digital 5.1, Dolby noted.

For compatibility with two-channel audio systems, the Forum specified multiple player requirements. First, players must downmix all required multi-channel formats to two channels. Players will also be required to decode two-channel PCM soundtracks (at a minimum of 96kHz/24-bit performance) that have been compressed with MLP lossless-compression technology.

Alternately, studios have the option to include separate two-channel Dolby or DTS mixes on discs.

DTS ++ Lossy refers to an assortment of DTS audio technologies, but the one that is mandatory is DTS’s core technology, which delivers 5.1 discrete channels at a data rate up to 1.5Mbps for compatibility with existing DTS 5.1-channel decoders and digital SP/DIF connections.

HD DVD OPTIONAL FORMATS

One optional format is multi-channel PCM that has been compressed with MLP lossless-compression technology. The MLP soundtrack could contain up to 7.1 or more channels. The upper limit of channels hasn’t been defined. Although the format’s upper data rate limit hasn’t been defined yet, the potential exists for all channels of a 7.1 soundtrack to perform at 192kHz/24-bit levels.

This format would require consumers to buy a new decoder if one isn’t built into the player.

Other optional HD DVD formats are part of the DTS++ Lossy family and are compatible with current 6.1-channel DTS ES Matrix and Discrete decoders and with DTS 96/24 decoders. DTS++ Lossy also supports 7.1- or more channels.

DTS Lossy soundtracks with 6.1 or more channels will be playable in 5.1-channel form through existing DTS 5.1-channel decoders. The 6.1 soundtracks will be reproduced in 6.1-channel form through existing 6.1-channel DTS ES decoders. Though the data rates of DTS Lossy soundtracks could reach 3Mbps, according to DTS information presented to the Forum, they will include a 1.5Mbps component for compatibility with current DTS decoders.

A new decoder would be needed to reproduce DTS Lossy 7.1 soundtracks in discrete seven-channel form.

Another HD DVD option is DTS++ Lossless, which uses lossless compression to deliver a minimum of 5.1 discrete channels (with no limit on the maximum number of channels) at up to 192kHz/24-bit performance levels. When decompressed, the soundtrack is bit-for-bit identical to the uncompressed original. Datarates could exceed 12Mbps, DTS said. Consumers would need a new decoder to hear this option at full quality, but because the format contains a Lossy DTS 5.1 signal at its core, existing DTS decoders will reproduce the lossy content.

BLU-RAY MANDATORY FORMATS

The Blu-ray Group has specified three mandatory player formats. Although the group is open to mandating additional formats, “no work is going on” to do so, said a technology strategist for one of the group’s manufacturer members.

The three mandatory technologies are DTS 5.1, Dolby Digital 5.1, and eight-channel (7.1-channel) 96/24 PCM. Only the eight-channel PCM soundtrack would require consumers to invest in a new decoder.

For compatibility with two-channel sound systems, players will likely downmix the Dolby Digital and DTS 5.1 soundtracks to two channels, although the Blu-ray spec doesn’t mandate downmixing. In addition, content providers can include two-channel PCM, Dolby Digital or DTS on discs to provide compatibility with two-channel systems.

BLU-RAY OPTIONAL FORMATS

Several options include uncompressed 5.1-channel 192kHz/24-bit PCM, which players could downmix to two channels if a manufacturer chooses to include that capability.

The other options include all of the DTS++ Lossy and Lossless technologies that are also options in HD DVD players. The options’ compatibility with the installed base of existing decoders is the same as it is with HD DVD.

As with HD DVD, therefore, some of Blu-ray’s optional DTS++ Lossy formats are compatible with current 6.1-channel DTS ES Matrix and Discrete decoders and DTS’s 96/24 decoders. Lossy 7.1-channel DTS is also an option.

The 6.1 and 7.1 DTS ++ Lossy formats will be playable in 5.1-channel form through existing DTS 5.1-channel decoders. The 6.1 soundtracks will be playable through existing 6.1-channel DTS ES decoders. Though their data rates could run to 3Mbps, the Lossy options will include a 1.5Mbps component for compatibility with current DTS decoders.

A new decoder would be needed to decode DTS 7.1 Lossy soundtracks in discrete seven-channel form.

Another DTS option is DTS++ Lossless, which delivers 5.1 or more discrete channels using lossless compression to deliver compressed soundtracks that, when decompressed, are bit-for-bit identical to the original. Data rates could exceed 12Mbps. Consumers would need a new decoder to hear this option at full quality, but because the format contains a Lossy DTS 5.1 signal at its core, existing DTS decoders will reproduce the Lossy content.