Low Audio Levels

forumsettings wrote on 9/25/2008, 11:26 AM

I rendered my video as an AVI with uncompressed 48kHz/16bit PCM audio in my primary NLE (not Vegas). When I look at the wave and preview the disc in DVDA the audio is fine. When I view the burned disc in a standard DVD player, the audio is low. Turning the TV volume all the way up does not begin to distort the audio. I copied the VOB file to my hard drive and renamed it to AVI. I opened this file as well as the source file in Sound Forge and there is a significant difference between the levels. What could be causing this? Thank you.

Comments

Terry Esslinger wrote on 9/25/2008, 12:29 PM

From a previous JohnMeyer post:

When encoding to AC-3 in Vegas, the defaults will make your audio too quiet. To fix this make the following changes:

1. In the Render As dialog, select Save As Type: AC-3.

2. Click on the Custom tab.

3. On the Audio Service tab, set Dialog Normalization to -30 dB.

4. On the Preprocessing tab, set BOTH of the Dynamic Range Compression settings to None.

5. Save this as a Template so you can use these settings in future renders.

You will now have an AC-3 file that matches the level of the WAV file.

forumsettings wrote on 9/25/2008, 1:28 PM

I am not using Vegas as my primary NLE. The audio levels of the rendered AVI file are great. Something is happening within DVDA. Thank You.

johnmeyer wrote on 9/25/2008, 2:58 PM

Terry gave you the correct answer. Whether the audio encoding is done in DVDA or in Vegas, the default AC-3 settings will often result in audio levels which are too low. There are dozens and dozens of posts in the Vegas forum about why this is the case (short version: it is not a Vegas/DVDA bug, but a function of the AC-3 spec). The solution is to encode the audio in Vegas, rather than DVDA. My strong recommendation is that you ALSO always encode your video in Vegas, not in DVDA, because you have many more options which can improve the quality.

Finally, if you don't like any of those alternatives, then do the audio encoding in some other application. DVDA will accept AC-3 from pretty much any application and will not re-encode the result.

Yet another alternative is to encode the audio -- again in some other application, including the one you used to create the AVI -- as a PCM (i.e., WAV) file. DVDA will put this directly on the DVD without altering it.

As always, go to the File -> Optimize DVD dialog in DVDA and look at each video/audio asset to see if DVDA is re-compressing. If you do everything correctly (i.e., encode things outside of DVDA) you will see green check marks in both the audio and video columns for each media asset, and DVDA will simply do a prepare (convert to VOB files), something that usually only takes 2-3 minutes, instead of hours.

forumsettings wrote on 9/25/2008, 3:23 PM

Thank you John and Terry. As I mentioned in my initial message, my audio is PCM.

johnmeyer wrote on 9/25/2008, 5:26 PM

You did mention that your audio was PCM. However, I'll bet if you go to the Optimize dialog in DVDA, as I recommended, you'll find that this is being converted. You'll need to change the project settings in DVDA to stop this from happening if indeed you want to keep the PCM audio in your DVD. If DVDA uses the default settings, it will compress this audio to AC3, and we've already covered in the previous posts what happens then.

So, if you see something other than a green check mark next to your audio in the Optimize dialog in DVDA, you now know what to do to correct your problem.

musicvid10 wrote on 9/25/2008, 8:14 PM

To expand just a bit on johnmeyer's always excellent observations, I want to add the results of my somewhat exhaustive tests on precisely the same subject, using the AC-3 Pro 5.1 Encoder in Vegas Pro 8.0c (along with many others, I do not prefer rendering in DVDA5, because I have no control over the render options):

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

Everything else you can leave at the defaults without concern.
Hope this helps a little.

P.S. You don't want to include PCM audio on a DVD or BD, unless you've got a lot of room so spare. It takes an average of 5X the disc space, which could be better utilized by video bitrate.

forumsettings wrote on 9/26/2008, 8:02 AM

Thank you to everyone who posted here. Although I did not use Vegas for this video, the principles apply. In the end I used TMPGEnc Plus to render an M2V file. My audio jumped up about 5dB and we were pleased. Thanks again. I always appreciate it when strangers take time to help.

musicvid10 wrote on 9/26/2008, 7:55 PM

You are welcome. And at the risk of speaking for others, please don't consider any of us as strangers. Glad you got some useful advice, even if it wasn't directly related to your workflow.