why is AC3 volume so low?

[rastoma]

I posted a similiar post about AC3 problems but only 1 person wanted to help with an answer... it seems everyone else only likes posting questions that are covered 100% in the guides instead.

I would just like to know how can the people on here that make DVD's using AC3 audio actually hear the finished product? How are they making AC3 audio files that are worth watching the DVD with?

I can live with a hollow sound, I just can't understand why the volume is so low. I can extract the sound with Goldwave and double the volume using Goldwave and then when I create the ac3 with Besweet it's still just as low as the times I try converting without doubling the sound. I am using just L and R sound. I have tried Vegas 4 and it produces identical ac3's... very, very low volume (and hollow sound). I just need these disc to be as universally compatible as possible is the reason I'm not using another format.

So just what is the secret to creating an ac3 when you use what everyone else is using and follow the exact same steps?

[bugster]

I don't make my own Ac3's so I can't actually answer your question as such. However I would like to ask if you have considered that there may be nothing wrong with the Ac3 tracks you are producing and that the fault may be in your DVD player/Ac3 decoder-amplifier?

Just a thought.

[aceof1]

Are you backing up a dvd? and is the sound lower then the original?

[Cornucopia]

Coupla things...

More info would help. Are you making AC3's from scratch (indep production, home videos, caps) or are you just converting/backing up?

"Hollow" sound coud be just how you're hearing it on your system (don't know what that's like), or it could be a bad downmix from 5.1, or it could be something out of phase. Hollow sound is usually bad and I wouldn't let that continue.

When you say low volume, it could very well be the effects of using the std. DIALNORM setting (~ -27db) which is a setting flag in the AC3 stream which tells your player what level to set the volume to. This is a well-known FEATURE of AC3 that allows one to set the volume's dynamic range compensation so that most all video dialog is at about the same level. This removes the annoying occurrence of levels shifting up and down depending on the program (as happens in CD audio and broadcasts).
In a sense, AC3 audio is NOT too quiet, everything else is TOO LOUD. I guess, if you really wanted to make your AC3's "louder", you could adjust the DIALNORM setting, but unless you know what you're doing, I wouldn't recommend it. Check out
Dolby's Website to find more info on AC3 and the DIALNORM settings.

HTH,
Scott

[VidGuy]

Actually, as far as I know, this is a well-known issue with Besweet (I don't quite understand why it hasn't been fixed yet, but then, I don't write audio code either - it's been this way for a long time).
Personally, I use the AC3 encoder from Scenarist, which doesn't have this problem, but you can probably get around it in BeSweet by guestimating in some way an amplification and having it amplify first.

[mkelley]

Actually, the BeSweet problem is a problem with *reconverting* compressed sound. BeSweet will not lower the volume on uncompressed sound, like PCM, but if the sound has been previously compressed (MPEG, for example) and you use BeSweet to convert to AC3 you are further compressing and hence the problems.

I use BeSweet with no difficulties on all manner of PCM files and the sound is just fine (too loud, indeed, on .WAVs ripped from CDs -- I have to lower it using Sound Forge before I can use it in my menus). What is your original source? If it's compressed, can you get it before it's compressed (for example, you shouldn't be using TMPGEnc to create sound streams in any manner -- far better to get the WAV using AVI2WAV or some such).

[VidGuy]

Interesting..... Yeah - I'm converting mp2 files to ac3 (going through WAV, but of course, it's a WAV based on previously compressed data). Doing it just to have a "legitimate" DVD in some cases since having only an mp2 track is technically a violation...

[txpharoah]

Besweet does a bad job for many people on AC3 encoding. That's why I stick to using SoftEncode or letting DVDit! PE convert for me.

[vhelp]

Hi guys..

@ rastoma..

TMPG and MPEG-2...
* Have you tired encoding your source to a video-only file ie, .m2v,
* and then feed the AC3 audio to HeadAC3 and encode to .MP2 audio,
* and then finally, MUX them together into a final .MPG file ??

I wish BeSweet was the best sounding quality tool to use, but I've heard
that HeadAC3 is just too good a deal to pass up in final sound quality
I wished for BeSweet, becuase it has the ability to be used via command-line
mode, and I could write some GUI's and/or personal tools to benefit my
needs, but I really want maximum quality and at lowest bitrate I can
afford to use. I use either 112k or 128k but people will usually prefer you
to use a min. of 192k - but that will depend on your ears of choice and
the source, oh, and your skill-level

-vhelp

[rastoma]

thanks all for everyone's reply.

sorry about not being more specific.

i am taking AVI's and creating DVD's out of them. I extract the audio from the AVI as a WAV file. then I take the WAV file and convert it to AC3. again I have used vegas 4 and besweet both and both do the same thing... make the volume so low that on full volume on my pc and TV both it's still not loud enough to really hear everything. the extracted WAV is excellent sounds.. sound volume is perfect.

i have tried the gain function in besweet and i have also used goldwave to double the volume on the wave first before converting to ac3... no affect.

some of the wav's are extract at 44100 and i resample to 48000 but the resampled wav still is perfect in audio quality and volume.

[Gregg]

Hi,

I have the same problem as Rastoma. The WAV from AVI is OK. After converting to AC3 with BeSweet the volume is low. I think DVDIt gave me better results but still the sound is lower than the WAV.

Cheers!

[bennetm3]

Not much help - but I have extactly the same problem converting a wav file to Ac3 using Softencode.

The problem only seems to have started occuring recently, and it seems to be since I changed from Win-Xp to Win-2000. I am currently trying to find out why !

Any ideas on this problem would be greatly appreciated.

[Limulus]

great topic. i got the same problems in audio when doing DVDRs from VHS.
the WAVs i am editing seperately for a DD 5.1 sound are pretty cool (still "fake" surround though) but main problem is ac3 aint loud enough in the end. is there any kinda standards for audio level in ac3 sound for dvds ?

[Metaluna]

thanks all for everyone's reply.

sorry about not being more specific.

i am taking AVI's and creating DVD's out of them. I extract the audio from the AVI as a WAV file. then I take the WAV file and convert it to AC3. again I have used vegas 4 and besweet both and both do the same thing... make the volume so low that on full volume on my pc and TV both it's still not loud enough to really hear everything. the extracted WAV is excellent sounds.. sound volume is perfect.

In Vegas 4, try this: After you tell it to render to AC3, go into the custom AC3 settings. You will get a tabbed dialog box with lots of options. In the second or third tab, there is a checkbox called "Audio Production options" or something like that, and near that will be a drop down menu box that says something like "105db room monitor". Make sure this checkbox is checked and leave the 105db setting as-is. Then save this custom template and render the audio. I would be interested to know if that fixes your problem.

If you compare the Soft Encode settings to the Vegas 4 settings, Soft Encode has the box checked by default, while the Vegas AC3 Encoder does not. I observed the low volume problem in Vegas, but not in Soft Encode. Coincidence? I tend to doubt it. I'll have to try Soft Encode with the audio option unchecked and see if the low volume problem happens there.

So, this fixed the "low volume" problem in Vegas for me. The question is, what exactly does this option do, and how do you get BeSweet to do the same thing?

[Cornucopia]

Yeah, Metaluma, that "Audio Production" stuff goes along with the DIALNORM stuff that I was talking about.

Scott

[Dennis1968]

BeSweet has been a problem as well, I have stuck with imported AC3 created with SoftEncode

[scottb721]

Not exactly the same, but when I do DVD to SVCD backups I have to increase volume 300% in TMPGE to get decent volume from the SVCD.
Otherwise I have to crank up stereo or TV.
Even then, I still have trouble hearing my SVCDs on my work laptop.

[funkguy4]

When you go to the WAV file, normalize the volume to something like 200%, and it should come out fine!

If your encoder doesn't let you do this normalize thing, just load it up into VDub and it can do it.

[digitalmaster]

I never had issues with BeSweet and AC3 Machine increasing the volume 5-8DBs when I checked the gain box. Always creates a louder AC3 file.
Do you have the codec called "AC3 Filter" installed? This has a volume control in the codec settings. This may be the issue. I also had a volume issue once with AC3 when there would be no volume at all. I installed the latest DirectX and the issue was resolved.