The Dolby Digital master is always produced on the dubbing stage at the end of the final mix of the film. During this process, the DD master is A/B compared to the 24 bit "printmaster" mix coming directly from the mixing console in real time, with the picture running. I have never heard any volume differences during this comparison; the only difference I routinely hear is a sound quality degradation due to the DD encoding. What this means in practical terms is that at least at it's creation, the DD master has the identical volume level that the film was mixed at. The DTS encoding is always done after the fact, and the film's mixing engineers do not routinely listen to this master.

As an aside, film mixing consoles do not have a "monitor volume" control that sets the playback sound level that is heard. The volume of the film is literally controlled by the engineers mixing the various sound units to a volume that is "appropriate" and what the film's director wishes. Some want their films mixed louder, some not so loud. But at any rate, on a film console (unlike a traditional music recording console), the volume level of the mix you hear is literally what it will be in a cinema.

[This message has been edited by soundhound (edited February 26, 2003).]

Here are some links:

http://www.smr-home-theatre.org/optimode/page3.html
http://www.dolby.com/tech/

BoB:

Thanks for the kind words regarding links - glad they helped.

The article on WireHed wasn't really definitive on a lot of issues IMO, pretty much seemed to follow the usual 'it sounded better to me, and here are some facts' format. Nothing really new or different. They handily omitted some facts too, like the question where the 0.6 db boost on the DTS 'shootout' CD came from and the fact that DTS hits -3db at 15khz and 754 kbps (the typical DVD rate) among others.

My take on it is that DTS may sound better (from my experience) but whether it's more accurate or not is not proven and in any case it does have issues of it's own AND consumes a truly hogish amount of bandwidth compared to the rather small improvement over DD.

I'd like to see DTS at 448 kbps, but I doubt the codec could produce anything worthwhile at that datarate. I bet a codec with the efficiency of DD and a higher datarate, maybe just an AC-3.1 where higher datarates are defined would beat either current solution. I'd also like to hear what Dolby 'E' (2mbps datarate) might sound like, but I doubt consumers will in the near future.

D.D may be more accurate to the master, and without hearing comparisons myself I just have to take people I trust, (Like SH’s) word. But the reason I was asking the volume question is that repeatedly seeing that argument that DTS is recorded hotter so we simply perceive it as ‘louder = better’ has always confused me as to its merits as a valid point. I have a comfort zone for my ears regardless of the media or version that I constantly adjust for. If I’m ready to ‘dig in’ to a movie and it’s not to late, regardless of the ‘level’ it was recorded at. I will set it to the level I wish to experience. So unless the adjustments such as Charlie’s links on how the DD decoders are set to compensate dB levels particularly on THX equipment, or on the dubbing stage itself ‘Dialogue normalization’ factors in a manner I’m not grasping.

Don’t I just tend to up my dB to the level my ear ‘likes’ for DD.
And pull it back if it’s overboard on a DTS version.

My volume knob is not fixed beyond my control. I set the level so how should that factor into equating that I simply might be choosing DTS as a preferable solely because its recorded louder?

You probably prefer the DTS because it does sound better. I preferred it myself. The point I have been trying to make (and what was borne out at the DTS vs DD shootout I participated in with the "Terminator II" reel) is that beyond the hype, smoke and mirrors, they both can be accurate to the original master when they have to be. I know that DD degrades the sound, and there is no reason to think that DTS doesn't also do so, but probably to a lesser degree.

From a marketing point of view, it is necessary that your product stands out from the competition. Whether DTS does this by actually sounding better, or by manipulation of the master or a combination of both, only they know for sure. All we know is what they say, and barring the opportunity of taking a sound file to DTS for encoding and then doing a comparison to the original, the debate is bound to continue.

[This message has been edited by soundhound (edited February 26, 2003).]

Interestingly that is possible, since (if I understood correctly) the DTS CAE-4 encoder has been available to studios (and maybe the public, with enough $$$ ?) since 2000, so it seems like an interested 3rd party could hold a thorough shootout, if motivated and backed.

EDIT: [added link]

http://www.dtsonline.com/proaudio/cae4.html


[This message has been edited by charlie (edited February 27, 2003).]

I have not seen a DTS encoder at any studio sound department I've been at, but then again, I'm usually not concerned with sound lay-back issues, and haven't specifically looked for one. I'll make it a point to ask to have a file encoded if I do get the chance. I still haven't purchased the Dolby Digital encoding software because I haven't had a request for a DD encoded copy a music soundtrack yet.