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A New Definition of Sound

26 Oct, 2007 By: Chris Tribbey

Remember DVD audio? Simple, wasn't it?

You had either a Dolby Digital or DTS track on your discs. And any DVD with a 5.1 soundtrack was considered top-notch.

But with HD DVD and Blu-ray Disc, audio has become more complicated, leaving the average consumers wondering what they need to appreciate the full experience. True HD, Dolby Digital Plus, DTS-HD, higher bitrates and 7.1 (seven!) surround sound. Your typical home theater fan may wonder if it's worth figuring out.

Yet high-def audio is far better than anything DVD can offer, studios and high-def experts insist. Consumers just need a little direction.

“You really can't do better than lossless, master quality, which is what you get with these new audio codecs delivered on high-definition discs,” said Daniel Silverberg, VP of HD media development for Warner Bros. In layman's terms: High-def audio can deliver almost exactly what was originally recorded for the movie, and little — if anything — is lost when the disc is played at home. High-def players are programmed to decode the various high-def audio options offered, giving consumers a superior sound experience.

“When we encode a title, it is bit-for-bit identical with the source audio,” Silverberg said. “The good news is that both the Blu-ray and HD DVD formats support lossless audio, and WB tries to incorporate lossless multi-channel wherever possible, depending on the type of release and the source material.”

He said Warner has “been using Dolby True HD for HD DVD and are transitioning to that codec for its Blu-ray titles.

Both DTS and Dolby Digital have created new audio formats for high-def, using the disc space available on the greater-capacity discs, allowing for less-heavily compressed audio tracks.

Kevin Collins, Microsoft's director of HD DVD evangelism, said every HD DVD player must support two of the advanced audio codecs: Dolby True HD and Dolby Digital Plus.

“U.S.-based HD DVD studios always use Dolby Digital Plus or Dolby True HD on all their titles,” he said. “All HD DVD players decode those audio codecs in the player and provide the consumers with a high-resolution audio experience that far exceeds DVD.”

For Blu-ray, DD-Plus, DTS-HD and True HD are optional on set-top boxes, but both standard DTS and DD are required, as are Pulse Code Modulation (PCM) tracks, which deliver the master audio track recorded by the studios.

Say what?

Adam Gregorich with Home Theater Forum helped clear things up.

“Dolby Digital is the equivalent of what was on DVD, but usually at a higher bitrate on HD formats,” he said. “Dolby True HD is lossless audio that is supposed to match the master bit for bit. The trick is both [DD Plus] and True HD can be encoded at 16 bit or 24 bit. Here is where it gets contentious.

“A lot of people claim that True HD is better because it is lossless, but some sound mixers [and] designers are saying that they can't tell a difference between a good (DD Plus) track and the lossless True HD track on a movie that they mixed.

“It's just one more thing for early adopters to argue over at this point.”

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