AC3 Encoding Problem- Lowering Volume?

Matt Grunau

Matt Grunau

Adobe Demigod
Hi all. I have a project set up as stereo blending CD music with 2 mic'd cameras (cheerleading competition). The total db of the background cheering is between -9- -12 and the CD track is -9 which when all blended brings the overall output to beween -6 and -3db. WHen I switch the project to 5.1, I readjust the volumes up for the rear speakers (which are now the crowd noise) and the fronts (the CD track) and make them all between -6 and -3db, and I drop the center down to around -15 (sounds better too me). The final result is just as loud in surround as the stereo mix. But when I render out and AC3, the volume cuts by almost half. If I render as a .wma, the volume is exactly the same as it plays when previewing in Vegas. I authored a DVD and then opened the .vob in Vegas and the audio levels were very low in the waveform displayed. The stereo version of the .vob has the audio levels higher and of course, they play much louder.

Is there something I am doing wrong, or a setting I need to change (there are A LOT of surround settings when you go to Custom, though I stay with the 5.1 template) in order to have the volume play from the DVD as loud as it plays in Vegas?

Also, is there a reason why AC3 files do not preview in DVD architect as surround? THey play, but not in surround mode. I thought this may be for preview purposes only.

Thanks for any help, and an explination of some of the custom settings (which are not in the manual before that is brought up) for the AC3 encoder so I can get the sound I am looking for?

THanks again.
 
It will be fine when you play the DVD. The audio on DVD is set at a much lower volume than on a CD or from other sources, because the dynamic range is much, much larger.

However, from Help:

My AC-3 audio files are quieter than my PCM audio files, even though they were rendered from the same project. How can I make the levels match more closely?

The AC-3 encoder can be configured to perform dynamic range compression.
When rendering your AC-3 files, change the following settings in the rendering template:
  1. In the Render As dialog, choose Dolby Digital AC-3 from the Save as Type drop-down list.
  2. Click the Custom button. The Custom Template dialog is displayed.
  3. Select the Preprocessing tab.
  4. From the Line mode profile drop-down list, choose None.
  5. From the RF mode profile drop-down list, choose None.
  6. Click OK to close the Custom Template dialog.
  7. Click Save to render your file.
 
David Jimerson said:
It will be fine when you play the DVD. The audio on DVD is set at a much lower volume than on a CD or from other sources, because the dynamic range is much, much larger.

However, from Help:

My AC-3 audio files are quieter than my PCM audio files, even though they were rendered from the same project. How can I make the levels match more closely?

The AC-3 encoder can be configured to perform dynamic range compression.
When rendering your AC-3 files, change the following settings in the rendering template:
  1. In the Render As dialog, choose Dolby Digital AC-3 from the Save as Type drop-down list.
  2. Click the Custom button. The Custom Template dialog is displayed.
  3. Select the Preprocessing tab.
  4. From the Line mode profile drop-down list, choose None.
  5. From the RF mode profile drop-down list, choose None.
  6. Click OK to close the Custom Template dialog.
  7. Click Save to render your file.
Click to expand...


Where did you find that??? I searched the help files very very thoroughly, and didn't find anything like that!

Or, I should say, what seach criteria did you use? I swear I looked like mad for any info like that. Got plenty on the uses of setting up Bus and hardware/software settings, but nothing so specific as that.

Thanks a bunch. And, if that is the default, do I want to change them? Will that cause any probs/isues I should avoid?
 
Last edited:
I just used "AC-3." Header is "AC-3 Levels Drop When Rendering."

The only problem I can see is you lose dynamic range. One of the reasons AC-3 volume is so low is because surround mixes have everything from the subtlest of the subtle to the most booming explosives. If the volume is too high, you can't do either.
 
David Jimerson said:
I just used "AC-3." Header is "AC-3 Levels Drop When Rendering."

The only problem I can see is you lose dynamic range. One of the reasons AC-3 volume is so low is because surround mixes have everything from the subtlest of the subtle to the most booming explosives. If the volume is too high, you can't do either.
Click to expand...

I was using AC3, and Surround. Heh.

If you want very loud instances (booming explosions), then how would you get them? I would think the mix would look like it would be clippling to get just that sound loud enough. I can see how the subtle things would be subtle, but I cant understand how you could get loud volumes approaching 0db with it lowering the overall volume.

Still new to the surround thing.

THanks again.


EDIT: If I wanted to leave the 5.1 to default, should I then lower my 2 channel mixes to be the same volume? I would like to be able to have more than one audio track on the DVD. If I should lower the stereo track, is there a way based on how much the AC3 will be lowered to do this? Maybe cut it down an additional 6 dbs? Or is there a formula to get it exact?

Lastly, should I be able to hear the surrond mix in DVD Architect?
 
Last edited:
You can do an AC-3 stereo mix if you want to match the levels.

Not sure about DVDA playing back in surround. There's no audio device preferences tab, so maybe not.
 
You must log in or register to reply here.
Back
Top