Dolby DD+, Dolby TrueHD, and DTS HD Master are three new formats that are supported by the new HD DVD and Blu-ray Disc (BD) standards. Audioholics takes a look at one of them - TrueHD - and gives it the once-over.

What is TrueHD? Like DTS HD Master, it is a lossless, bit-for-bit duplicate of the studio master soundtrack. Listening to a TrueHD soundtrack, you will not be hearing anything different than what the movie’s sound engineers heard. That is, of course, assuming that your home theater’s audio equipment and room are up to the task.

TrueHD supports up to 8 full-range channels of sound. In practise, though, one would be used for the bass, just like the “.1″ in “5.1″ surround sound. TrueHD stores the original studio soundtrack, without losing a single bit of it. However, it does pack the data closer together using a lossless compression scheme. This does not affect the sound quality in any way. TrueHD also uses a bit rate of up to 18Mbps. Though in practise, that sounds like a bit much.

HDMI 1.1 can transport up to 8 channels of digital 24bit / 96kHz audio, which is how some BD and HD DVD players today output the TrueHD or DTS HD Master soundtracks. Or they put them out on the analog outputs after converting to analog. Which is why the inclusion of 5.1 analog outputs is strange - shouldn’t it be 7.1? As well, another option that the Toshiba players use is to convert the soundtrack to normal lossy compressed DTS 5.1, in case your receiver can’t handle any of the other formats. If your receiver or pre/processor supports HDMI 1.3 though, you’re in luck. HDMI 1.3 can transport the whole TrueHD (and DTS HD Master) soundtracks digitally. However, I don’t know of a single receiver or pre/pro today that has HDMI 1.3 support.

Dolby TrueHD Overview