Normalize audio level (during export to AC3 audio) -- what should it be?

Question

Hi. New to STP (v3) in general.
Someone recommended, when I reported having issues with my burned DVDs stuttering at certain places, consistently, to both use a constant bit rate for video when encoding an MPEG2, as well as making the audio an AC3 file at 256K.
Using soundtrack pro, the 256K part I can figure out. What I'm worried about is this option (that you can't seem to bypass completely) called "dialog normalization". I have no idea what that should be set at. It defaults to -27. Now, I do all the audio work in the original edit, so I don't want this encoding to do any additional normalization. So what's the deal?
If it matters, my file that will be encoded is an uncompressed (in DV terms) AVI that was edited and rendered on a PC. I know this is not optimal for Macs, but I know it can work. So the video will be made MPEG2 with DVD studio, and I want to encode the audio as AC3, at 256K. Just for safety. These are film festival screeners, so the quality doesn't have to be maxed out.
So, where do I want this "dialog normalization" set to? In the original film, most sounds are between -18 and -6 dB, generally, rarely approaching 0. This particular film is a toughie here because there's little dialog period, mostly sound FX and music.

Answer 1

Dialog norm shouldn't be confused with Normalization as it is usually used.
Dialog norm is metadata popularized in AC3 (Dolby Digital) files in an attempt to have the DVD player adjust its volume so that every DVD has the same loudness. If you know the [LEQ(m)|http://www.dolby.com/assets/pdf/techlibrary/34_TV_LoudnessAES.pdf] of your track, then you should set the dialog norm to that level. LEQ(m) is a measurement of "loudness equivalence". It's invented by Dolby, but they and many others are pushing it as a way to equalize the listening experience in the face of louder and louder sounding mixesl The setting of -27 is the default setting. Unfortunately the only way to measure LEQ(m) is with an [expensive box from Dolby|http://www.dolby.com/assets/pdf/techlibrary/123_pa_br_0206Model737.Spec.pdf]. There is [software|http://www.channld.com/audle.html] that will measure [LEQ(a)|http://www.google.com/search?client=safari&rls=en-us&q=leq(a)&ie=UTF-8& oe=UTF-8], but that may be slightly different than LEQm. It might be good enough for non-broadcast.
I haven't used the STP AC3 tools, but I have used Dolby encoders in other software. If you don't know what you're doing, I would recommend setting it to OFF or -32 (if that is the highest number available). That way the DVD player will play your track at its full volume without any attenuation.
Here is a short excerpt from the [Metadata pdf|http://www.dolby.com/assets/pdf/techlibrary/18Metadata.Guide.pdf] available at dolby Labs.
+The dialogue level parameter (aka dialogue normalization or dialnorm) within the Dolby+
+Digital stream provides a normalization value to the home decoder. This value lowers the+
+volume of the audio to a preset level, which aids in level matching from program content+
+to program content and media to media. The setting of this dialogue level parameter is+
+crucial to the proper operation of home decoders and provides three main functions:+
Dolby has [tons of information|http://www.dolby.com/resources/tech_library/index.cfm] if you want to educate yourself.
Hope that helps,
jim