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Quote Hugh:

Dolby Digital uses data reduction (often erroneously called data compression) as a means of making the file sizes more manageable for storage or transmission. But this has nothing to do with dynamic range compression.

I see. By the way, as you may know, in information technology, it is standard to refer to the kind of data reduction that you refer to as "data compression". So, for example, mp3 is referred to as a "compressed format", created by "data compression". But it is really, as you indicate, a way of encoding in order to accomplish data reduction.

Quote Hugh:

The metadata carried with Dolby Digital soundtracks has encoded information which states which of the several different dynamic range compressions curves that are available to impose if the user seleects DRC mode.

Am I correct in assuming that this works the other way 'round too in that on the set-up menu of any DVD player, DRC is made available as an option only if Dolby is enabled, or that even if DRC is made available as an option and is enabled when Dolby is not enabled, DRC will only be implemented during playback if Dolby is in fact enabled? I want to be sure that I can simply tell a viewer, a projectionist, or whomever to "turn off Dolby" in order to turn off DRC as well as any other processing that Dolby might do.

Quote Hugh:

Can I suggest you do yourself a huge favour and either spend the time and effort reading through the full set of Dolby's papers on Dolby Digital and its metadata, or just ignore it completely.

The problem is that I am, in fact, forced to deal with it, as I'm forced to use Apple's Compressor, and unfortunately, reading up on Dolby at Dolby's Web site is not going to help much. I will explain...

Perhaps you're not aware of this, but for audiovisual works outside of major feature films and TV programs, Apple's Final Cut Studio has become the de facto standard for post production (although Pro Tools is used to generate soundtracks for all sorts of works). Part of Final Cut Studio is Compressor, which encodes video and audio for DVD. Given the circles that I move in, I must use Compressor, as the other folks with whom I'm working simply won't accept my using anything else. This is why I asked if you would please look at Compressor's instructions for choosing Compressor's various settings for Dolby processing, to see if they make sense, to see which settings should be chosen, etc. It's not quite clear in Compressor in light of what I now know about Dolby, thanks to you. (Thank you.)

Quote Hugh:

In film mixes, the dialogue is generally lower (to allow more headroom for the explosions), typically around -24 to -12dBFS... The replay level is adjusted by the dialnorm metadata to set the nominal dialogue to -31dBFS. That is entirely separate from the industry conventions for the source recording.

I realize that. But if I'm including a normalized audio track on the DVD of my project, and am not indicating any Dolby processing when setting up for encoding to MPEG2 (for creating a DVD), then should I prepare my audio track such that my dialogue is around -31 dBFS, or rather, in the range of -24 to -12 dBFS?

If I understand you correctly, in a mix for film, dialogue will be placed between -24 to -12dBFS -- say, at an average of -18 dBFS; and so during the creation of the DVD of that film, "-13" will be indicated as the "dialnorm offset", thus putting the dialogue down at -31 dBFS during DVD playback. But that would suggest that in mixing the audio for my project, I should place the dialogue at -31 dBFS, so that it plays back from DVD at that level too, right?

Thanks.

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Robert Eidschun

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