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More Compatibility Seen Between HD Discs, Existing Audio Systems

Many consumers who already own an A/V receiver or preamp processor will have more options than previously thought to reproduce the highest bandwidth multichannel soundtracks of Blu-ray and HD DVD discs without junking their current components, Dolby Labs said.

Taking many in the industry by surprise, Dolby announced that consumers will be able to stream all of the discs’ mandatory and optional high-bandwidth soundtracks through a receiver’s single-cable HDMI 1.1 digital input from many of the new players. Initially, Dolby and receiver manufacturers believed that the only option for owners of existing receivers would be to connect multiple analog-audio cables between the receiver and player to hear the full potential of the high-bandwidth soundtracks.

HDMI 1.1’s ability to connect players and receivers, said Dolby Labs technology strategy director Roger Dressler, means “one less impediment to buying the new players,” especially for consumers who have connected the analog outputs of SACD and DVD-Audio players into their receivers’ multichannel analog inputs. Although the soundtrack-carrying HDMI outputs aren’t mandatory on high-definition disc players, he noted, it’s likely that the players will have them.

A single-HDMI connection will be possible, Dressler explained, because in all but perhaps the most basic players, all of the multichannel audio formats on a high-definition disc will be converted to PCM before exiting a player’s HDMI output. HDMI 1.1’s bandwidth is capable of simultaneously streaming an HD player’s video and a high-bandwidth soundtrack, and HDMI 1.1 inputs appear on many newer receivers and processors, all of which are already equipped to process PCM, Dolby pointed out.

The optional and mandatory soundtrack formats of the high-definition disc formats were announced last year, but Dolby and other industry insiders didn’t learn until much later that the high-definition players would likely spit out PCM.

PCM conversion will be needed in disc players that support the ability to play Internet-streamed audio content, such as director’s comments, while discs are playing, Dressler said. To accomplish that, the players must mix a disc’s soundtrack with the Internet stream, and to accomplish that, the players will convert the two streams to PCM. The players might also internally generate PCM sounds that would have to be mixed in as well, he said.

Although PCM conversion within a player isn’t mandatory, it is “the most practical way that the next-generation disc players achieve these new interactive features.” Dolby said in a statement. “Content makers are keen for it [mixing]”, Dressler added. “So we expect they will want mixing to happen.”

Like most industry insiders, Dressler continued, “I don’t think we understood that mixing would be a substitute for decoding downstream.”

Even if mixing doesn’t happen in a player, downstream decoding in an A/V receiver through a single-cable connection could be an option when new HDMI 1.3 specifications are finalized later this year. HDMI 1.3 connections could appear in first-generation Blu-ray and HD DVD players, marketers said. The 1.3 outputs would be able to stream the mandatory and optional soundtrack formats in their native form to future A/V receivers that would internally decode the high-bandwidth soundtracks.

The high-bandwidth formats include multichannel uncompressed PCM, lossless Dolby TrueHD, lossy Dolby Digital Plus, and lossy and lossless forms of DTS HD, formerly DTS++ Lossless.

Although Dolby will initially focus on selling its high-bandwidth decoders into high-definition players, DTS said it will aggressively target players and receivers. DTS cited the precedent of high-end A/V receivers to use 1394 digital inputs to accept DVD-Audio and SACD signals in the digital domain for processing. The receivers are marketed as offering superior decoding and processing.

“There could be different solutions to different-priced players,” Dressler added.

S/PDIF inadequate: HDMI in whatever flavor is the way to get high-definition players to spit out wideband soundtrack formats in digital form, Dolby said. That’s because the bandwidths of the players’ uncompressed-PCM formats, new lossless-compression formats and new lossy-compression formats exceed the capabilities of existing receivers’ single-cable digital S/PDIF inputs, which max out at 1.5Mbps. The data rates of the new soundtrack formats can run as high as 27.6Mbps.

For receivers lacking HDMI inputs, consumers would have to hook up six to eight analog cables if their receiver is equipped with multiple analog inputs. If their receiver lacks HDMI inputs and multiple analog inputs, consumers could opt to use the receiver’s S/PDIF input to stream a disc’s lower bandwidth mandatory multichannel formats, which squeeze through S/PDIF inputs and are compatible with receivers’ existing 5.1-, 6.1- and 7.1-channel decoders.

The mandatory formats for Blu-ray discs are the Dolby Digital 5.1 and DTS 5.1 legacy formats. For HD DVD, the mandatory formats are the new Dolby Digital Plus format up to 3Mbps and the new lossy HTS HD format. Dolby expects HD DVD players to incorporate built-in converters that will convert Dolby Digital Plus to 640kbps Dolby Digital 5.1 and lossy DTS HD to DTS 5.1 at up to 1.5Mbps.

Examples of the discs’ S/PDIF-incompatible soundtracks include Blu-ray’s optional six channels of uncompressed 192kHz/24-bit PCM at 27.6Mbps, HD DVD’s two channels of 192/24 PCM at 9.2Mbps, and both discs’ 7.1 channels of 96/24 PCM at 18.4Mbps, said Dolby.

The data rate of Dolby Digital Plus runs to 3Mbps on HD DVD and up to 1.7Mbps on Blu-ray discs in applications up to 7.1 channels.

Another Plus: Although the mandatory and optional high-bandwidth formats can deliver 7.1 discrete channels, owners of older HDMI-lacking receivers with 5.1-channel analog inputs won’t be left out in the cold. Any lossy or losslessly compressed 7.1-channel soundtrack carries metadata allowing producers to control down mixes from seven channels to five for receivers with five analog inputs, said Dolby’s Dressler. Uncompressed PCM tracks, however, lack metadata, so a player’s down mixing isn’t likely to “ensure a consistent result from player to player,” he noted.