AC-3 is unsatisfactory

RobT wrote on 8/19/2003, 7:15 PM
I've created a 1 hour and 23 min. long DVD with a simple menu. (scene selection) I was curious in the midst of devising the DVD in architect how big the project was. I hit the 'make DVD' button and then selected 'prepare DVD'. It, of course, informed me that all audio will be recompressed from WAV to AC-3. I then went down to the audio drop window and selected PCM just for the video itself (not the menu audio) It jumped my DVD percentage from 90% to 108% full. I then thought I could pull the WAV audio back into Vegas by itself, crank the volume up and render it as AC-3. I did this, pulled the AC-3 file back into DVD Architect to hear if the volume increased. It didn't.

My question is: Is there any way to increase the volume of an AC-3 (or WAV) file prior to rendering another AC-3 file? Why does it end up at such a low level regardless? I realize it's compressed, but it is not a desirable format to use for the main show. I'd much prefer PCM. Suggestions?

Comments

CrazyRussian wrote on 8/19/2003, 7:25 PM
Well, you asked for it, SUGGESTION: got to Dolby Digital's web site and RTFM!!!

P.S. "I realize it compressed".... compressed has nothing to do with it!!! Most of Hollywood DVDs are in AC3 format, and they are still damn VERY loud at times.
Hint: look into Gain levels
jeffcrow wrote on 8/20/2003, 12:56 PM
DVDA always converts audio to ac3 by default. And nobody has any problems with the ac3 audio being lower after DVDA does the conversion. I have heard of people rendering to ac3 using Vegas and the audio comes out too low. I tried that in the past and did not have that problem. Your DVD size increased because ac3 files are compressed and wav and pcm files are not, but then mp3 files are compressed too and the compression does not effect the volume. You may have changed the settings of the ac3 template, check that your Dialog Normalization setting is -24. Changing this can raise the volume, but can cause poor playback and make the file incompatible with some set top players, so I wouldn't mess around with it (this is based on what I read on another forum some time ago, don't have any personal knowledge of this).

If you just don't worry about the audio and let DVDA take care of it, you should not be having problems.
Eug7 wrote on 8/20/2003, 1:42 PM
I've made the same observation. The ac3 conversion diminishes the volume. What I've done in a couple of projects is render the MPEG in Vegas as an Architect and render the audio seperately as a wave. I import the audio into Cool Edit 2000 and amplify the wave 3db or 6db or somewhere in between that is approriate. After the Architect render the audio at least at the desk top is louder than if I had not gone through the amplification step. What I need to do and will do is an A-B comparision on the table top betwwn a non amplified wave and an amplified wave to verify.
thrillcat wrote on 8/20/2003, 10:12 PM
The DVD Standard for dialog in AC-3 format is -31db. This sounds low compared to TV, but it's the standard. Put in a hollywood DVD. Sure, it's loud AT TIMES, but the dialog is low, compared to tv. It's all in the dynamic range, which is much greater on DVD than via broadcast TV & VHS.

PCM audio is mastered louder, but is generally only used for music dvds in hollywood, which don't have quite the dynamic range as your typical blockbuster action flick.

You must set your dialog normalization levels correctly when encoding to make sure your dialog sits at -31db. See the link below, which I found in the AC-3 encoder Forum, which is where this topic is more suited.

http://forum.doom9.org/showthread.php?s=&threadid=56020
SonyEPM wrote on 8/21/2003, 9:59 AM
Also: AC-3 compression is source dependent- there is no one pefect setting for all audio projects. The defaults are what Dolby advised, but, especially if you want levels to match the PCM version, you'll likely need to tweak the AC-3 settings for each project. After you do this a few times you'll start to get a feel for which normalization etc settings work best for certain types of projects.

Also: Don't rely on software decoders when you are making compression decisions- the ONLY way to get it right is to burn to re-writeable media and test playback in a real DVD player. Save yourself some time and burn a short/typical piece of the soundtrack- once you get the settings to your liking save as a preset so you can recall these parameters.
JJack wrote on 8/21/2003, 10:12 AM
jeffcrow: I've been trying to get in touch with you re your post of 8/6/2003 1:35:40 PM on Scene Slection Menu. Would you be willing to contact me at Transformance@juno.com? Thanks
John_Cline wrote on 8/22/2003, 7:47 AM
Go to the last tab under the options for AC3 encoding in Vegas and change both instances where it says "Film" to "none." This will keep the encoder from changing the overall volume level of the file.

John
RobT wrote on 8/22/2003, 4:33 PM
Thank you all for your input. John Cline, you are the man! You suggested something that I didn't experiment with. Selecting 'none' by itself did not fix the problem, but when I also unchecked the filter boxes, it worked perfect. I went back and unchecked the filter boxes and left the drop window on 'film'....it didn't work. It was the combination of both of those actions taking place that did the trick. Thank you very much!

Now I've been lead to yet another agonizing puzzle.....In a new thread.
groovedude wrote on 10/31/2003, 3:24 PM
Will unchecking the filters make it less likely to play in all dvd players?