Audio peaks change from Vegas to DVD-A2?

JaysonHolovacs wrote on 7/19/2004, 8:45 AM
Anyone else notice this?

I create a video in Vegas. The waveform in Vegas has peaks of various heights but the highest ones are near this max range of the waveform without going over. This is the desired case for audio waveforms, right?

Then I render to mpg-2 and ac-3 and import into DVD-A. Looking at the DVD-A2 timeline window, I see the highest audio peaks now only span 1/3 or so of the audio range. Is the signal actually attentuated or is this just a display issue? Is the output volume actually reduced?

-Jayson

Comments

erratic wrote on 7/19/2004, 9:31 AM
To avoid a reduced volume use these AC3 settings:

Dialog normalization: -31 dB.
Dynamic range compression: None.
JaysonHolovacs wrote on 7/19/2004, 10:27 AM
Thanks for the info. Is there any reason I should not do this when transferring to DVD-A2? If not, then why isn't it the default?
erratic wrote on 7/19/2004, 10:43 AM
Good questions. Unfortunately I don't know the answer.

In Doom9's Forum someone wrote this guide: How to Properly Encode Dolby Digital Audio (AC3).

Way too complicated as far as I'm concerned, because the same guy also wrote this:
To make completely unaltered sound, you need DRC turned off, and dialnorm at -31 dBFS.
JaysonHolovacs wrote on 7/19/2004, 3:00 PM
Wow... this is a lot to cover. I basically understand it all, but taking it all in at once is a lot. But they only talk about audio programs... does anyone know if there is a way to do this within the confines of Vegas/DVD-A2? Or with free/inexpensive downloadable tools?

-Jayson
epirb wrote on 7/19/2004, 3:14 PM
to add to erratic's 1st post do this:
encode set to AC3
click on custom tab
on the fisrt tab set diag. norm to" -31"
on the last tab marked preprocessing
the line profile mode set to "none"
now save that as a preset ,mines called Stereo DVD Modified.
then use that one from then on, Got the advice from Spot and its helped tremendously with sound levels that seemed ok in Vegas but too low on DVD playback.
wobblyboy wrote on 7/19/2004, 6:24 PM
Because of the need for wide dynamic range for movies, the volume is normalized lower. When you render to AC3, click on custom, click on preprocessing, and change the dynamic range processing from film standard to music or light music. You could also change dialogue normalization setting. Play around until you get what you want.
farss wrote on 7/19/2004, 7:02 PM
If you need a really wide dynamic range, open the audio track in Sound Forge, Select All and view statistics. The RMS value of the track is close to what you should set the dialogue normalisation value to in the ac3 encoder.

I've tried this and it seems to work fine.
If you're audio is already compressed to within confortable lisetning levels then the previous advice is the way to go to keep it simple, that also in that circumstance works well.
JaysonHolovacs wrote on 7/20/2004, 7:13 AM
farss,

Any solution for the SoundForge deficient among us?


Last night I tried to do a sample with "Speech" style compression and a setting of -31dB. The volume was quite low. -31dB and no compression produces good results, but I couldn't understand why adding the compression made it so quiet. What should I do to counteract this? I can't set it below 31dB.

-Jayson
farss wrote on 7/20/2004, 7:30 AM
Do you mean you set the line level to speech in the encoder settings?
If so set it to none. If your audio is more compressed then you should up the dialogue normal value, -31 is probably way too low for something already compressed I think.
JaysonHolovacs wrote on 7/20/2004, 7:41 AM
farss,
I did end up setting it to none and rendering. It's okay, but maybe not optimal. I guess you need SoundForge to do more intelligent analysis?

-Jayson
farss wrote on 7/20/2004, 7:55 AM
Well I've gone down that path and its seems to come out OK but I'm far from an expert, all I can relate is my own limited experiments.
From the little I know ac3 encoding uses it's own compression system as it can cope with very large dynamic ranges, also from the same mix you can produce different encodes, say one for cinema release and one for home theatre.
Your best bet is to do a few tests, I remember SPOT saying they do an encode, listen to it, make adjustments and repeat until they're happy with it. ac3 is a fairly complex beast so i doubt there's one shoe fits all scenario.

Bob.