2 questions about audio.
 

[1] What's the difference between AC-3 Pro and AC-3 Studio? I've always selected Pro simply because it's listed above Studio in the menu.

[2] Under "Custom", "Audio Service", the value for Dialog normalization is -27 dB by default, when do I use any of the other numbers? What's Dialog normalization for?

Thanks,

Here are some answers from a very recent thread on the Sony Vegas forum asking the same question.

1. The studio version is not at all certified by Dolby labs.
Pro gives you customization options, Studio doesn't.
The Pro encoder is a Dolby Certified encoder while the studio version is not.
The Pro encoder works on Blu Ray while the studio encoder does not.
For DVD production, Pro always, Studio never.
The latter has a couple of bugs in DVDA that have never been fully addressed.

2. Dialnorm is an attempt to standardized dialog levels in movies.

Dialnorm on Wikipedia

To achieve the best of Dolby AC3, professionals use scales to arrive at the Dialnorm number.


Here are some settings from a user I trust implicitly if you want to make up a custom AC-3 template.

If you're doing AC-3 Stereo, you can ignore everything I say about the Phase Shift option, it's grayed out of course.

Dialog Norm at -31 (this sets it at unity gain)
RF and Line Mode DRC Off (WYHIWYG)
DC High Pass Filter On (this operates at <=3Hz and takes DC bias out of the mix)
Bandwidth Low Pass Filter On (this takes aliasing noise at >20kHz out of the encode, but it also lowered the rendered volume by -0.1dB in my tests)
90 Deg Phase Shift On (makes it easier for Pro Logic decoding on older equipment, Dolby says it is inaudible in 5.1 except in "very rare" cases)
Everything else can be left just as it is in the 5.1 DVD template.

Norris, thanks for asking a question I have also wondered about and thank you Mike for answering it! I think I have always chosen "Pro" and will definitely in the future.