HD Audio Formats

[admin_exported]

As a long-time fan of DTS over DD, I know how much personal view (and a better bass punch!) means when expressing a preference. But here's my question. Both DTS Master HD and DD True HD formats are supposed to provide lossless/uncompressed versions of the original theatrical sound mix. Why is there a difference, then? Or is there?
Over to the experts....

 

[Anonymous]

Yes, I'd be interested in knowing too. For instance, is it a function of the quality of your equipment? If you had a high end system would you notice any difference, versus a budget set-up? What do the WHF experts have to say on this?

 

[Anonymous]

ÿ

Modern feature films are mastered using 24-bit/48khz
audio to create an uncompressed PCM original. This sounds great, of course, but
takes up a lot of space. This master is then used to create appropriate
soundtrack options to suit a range of applications, such as the highly
compressed Dolby Digital soundtrack stored on cinefilm and still employed by a
large number of cinemas, as well as the majority of DVDs.

It's perfectly possible to put a full-fat 24-bit/48kHz
PCM original soundtrack straight on to a Blu-ray disc, but it takes up a lot of
space, and so tends to be reserved for discs that use two layers (BD50, as
opposed to BD25) and which employ more sophisticated video encoding systems. The
majority of PCM soundtracks are actually downconverted versions of the
original, stored at 16-bit/48kHz. They still sound good, of course -
uncompressed PCM is still miles better than heavily compressed Dolby
Digital.

One solution is to use the lossless packaging system,
either DTS-Master HD or Dolby TrueHD. This packages the 24-bit/48kHz original
master into less space, so it allows studios to both package soundtracks on
their Blu-ray discs more effectively, and also preserve the 24-bit original,
rather than accept a downconversion to 16-bit. As a (very) rough rule of thumb,
a 24-bit/48kHz PCM original packaged using Dolby TrueHD lossless uses about
half the disc space of the uncompressed audio.

In theory, a 24-bit/48kHz Dolby TrueHD or DTS-HD MA
losslessly packed soundtrack will be bit-for-bit identical to the 24-bit/48kHz
PCM master, and probably better than downconverted 16-bit/48kHz PCM. But which
is better between the Dolby and DTS variations on the theme? At the moment I
think it's impossible to call, in part because most (almost all) discs and
studios support either one or the other system, but not both. In theory, DTS-HD
MA allows for a higher bitrate, 24.5Mbps, next to Dolby TrueHD's 18Mbps, but
I'd be surprised if that translated into any dramatic sonic differences between
the two systems.

Perhaps it's something we should explore in the Ultimate
Guide To Home Cinema, due later this year (assuming we could find a disc or some content encoded in both audio formats, derived from the same master, and authored by the same studio, that is!). What do you think?

 

[Anonymous]

I think this is a terrific idea, Andy.

In the US, the BD of Top Gun has both tracks. It's region-free. No details are posted on the tracks for the UK release, yet. This might be the one to go for.

 

[Anonymous]

Hi Andy

I fully support this as I guess there might be lots of readers out there, me included, who have taken or are wanting to take the plunge but would like some real help in understanding this. It's so difficult to do a proper test yourself between the different HD audio formats.

 

[Anonymous]

Thanks both - I'll get hold of the disc (expenses, Clare?) and start working it up into a test/feature for the next issue. Any more recommendations on content gratefully received. BTW sorry if any of my earlier reply was teaching either of you to suck eggs. I get the impression from your replies that some of might have been.ÿ

 

[Anonymous]

Just wanted to say that I found this thread really useful too!! It would be great to have an article on the differences between all of the various audio formats for beginners like myself!

 

[Anonymous]

Regarding suggestions for other content, an overview trhat included the sonic qualities of DTS-Audio (ie Alan Parsons' On Air) as against DVD-Audio etc might be welcome, though I don't know if that expands the purview too much....For myself, I've been hugely impressed by the sonic qualities of DTS-Audio, so a box-out or similar on this would be most welcome.

 

[Anonymous]

Hey Kaotician!
Now, there's a can o' worms! I'm a fan of DTS-A, DVD-A and SACD, but given that they're essentially marginal products (albeit on the button for the audiophiles on this site) it'll perhaps be difficult to justify the time and space. I'd certainly like to see something on it tough...