AC3 is soooo QUIET!

[Xenogear900]

I have a bunch of different videos on my PC. A couple of them have ac3 audio. The audio on the AC3 ones is SOOOO MUCH more quiet than the other videos (without Ac3)! Why are these ones so quiet, it is hard to hear them. What can I do so the volume level is closer to the other videos?

My speakers are on full blast and its not really loud at all.

Xenogear900@yahoo.com

[nzjacob]

Install AC3 Filter. Load up its setting through the control panel and up the Master Gain. You can also up seperate channels.

[guns1inger]

AC3 has a wider dynamic range than PCM audio (or mp3 audio etc), so dialogue and softer sounds will sound quiet, and louder sounds will be about the same level as your other videos. AC3 filter is fine for playback on your PC, but if you want to change the levels for encoding to DVD you will have to demux the audio back to mono wavs, increase the gain on each one, then re-encode.

[nzjacob]

I use Canopus Procoder 1.5 to convert many AC3 AVI to DVD. I can simply up the levels in AC3 Filter before running Procoder and they come out with greater levels in my MPEG2 files. No demux etc required. It also means that when watching with WMP or such I dont have to move the volume knob to 11.

[fritzi93]

I use Canopus Procoder 1.5 to convert many AC3 AVI to DVD. I can simply up the levels in AC3 Filter before running Procoder and they come out with greater levels in my MPEG2 files. No demux etc required. It also means that when watching with WMP or such I dont have to move the volume knob to 11.

That has been my experience as well. Just up the Gain, normalise too if you wish. But I only ever played with a couple of AVIs with AC3. I merely configured AC3Filter, converted the AVIs, authored. The audio level is fine on the DVDs.

[Wile_E]

AC3 has a wider dynamic range than PCM audio (or mp3 audio etc),

Not from what I read on the Dolby website. All DVD movies, are normalized to -31db. This severely compresses the dynamic range down. Dialog is what is normalized up to 0db, from what I read. This makes dialog louder than everything else.

But for home movies that you and I have on tape, there is no way we can seperate dialog from whatever else. So we can either compress everything down to -31db, or leave it be. Probably best to normalize it down to -31db, so it is soft, like all other dvd's.

[adam]

No Wile_E you are confusing the use of those numbers. The film standard profile is actually a range between -26 and -31 and it seems that -27 is the most commonly used. But this applies to everything, not just the non-dialogue audio data..

What you are talking about is the method of implementing dialogue normalization. This is metadata which is set according to the relative level of the dialogue and the goal is to make the dialogue always hit the null band. This means its volume is neither increased nor decreased. Its actually not 0db it varies according to the profile used, but its usually 5db.

Basically the relative volume of dialogue is ascertained and then you set the dialnorm so that it places the dialogue level in the null band of your profile...in other words, EVERYTHING gets adjusted so that your dialogue level remains constant from each source since that is how people typically set their volumes. So if the receiver receives an audio source with a dialnorm of 5 followed by one of 6 then it knows to lower the volume on the second one since you would have adjusted your audio for the former.

So dialogue is adjusted to sit in the null band but its still going to fall in the middle of the dynamic range of the source and there will surely be many many more sounds that are much louder than the dialogue. The amount of "dialogue normalization" is just a reference for what must be done to the entire stream and its just to make it consistent with other audio sources, not to actually change its volume relative to other sounds like explosions and such. That's was dynamic range compression is for.

Yes AC3 does support a very wide dynamic range and that is exactly why downmixing it to 2.0 can cause dialogue to be too quite and explosions to be too loud. The solution is to apply dynamic compression yourself. Lots of DVD players have this, and I assume you can accomplish the same on your pc via plugins or filters from within your software player.

[Wile_E]

Yes, I think I am confused and still don't quite understand. When you say, that -27 applies to everything, what do you mean? If I were to load up a 2.0 AC3 file from a DVD and play it, the maximum level output would be -27db instead of peaking up to 0db?

I've been capturing my DV audio at up to -3db. When I encode this to AC3 with TMPGEnc, it sounds very loud in my player, compared to retail DVD's.

I then tried using the "dynamic range compression" option of TMPGEnc AC3 encoder. What it did was just set a flag in my encodings. My DVD player has an option to turn on/off this compression. It only works on files encoded with this flag.

[adam]

Normalizing something to -27db means to basically center your dynamic range at this point. All volume levels move closer to this point. You still have peaks and valleys on either end. Dialogue is put in the null band which is basicallly center of the dynamic range. Your quietest parts will valley below this about low as your loudest parts peak.

There are two ways to use dynamic range compression. The first is to just enable a flag as you say, and the amount of range compression is preset according to the profile you use (ie: film: standard.)

The other way is to apply a % of compression yourself. My DVD player has a "dynamic range compression" option and allows me to set it to 0, 1, 2, or 3.

[Wile_E]

So is normalizing the same or not as applying a % of dynamic range compression? How else would I apply compression to the audio file? I don't want to rely on people setting up their DVD players with compression ON. Also some players don't have that option.

[voxi]

AC3 has a wider dynamic range than PCM audio (or mp3 audio etc), so dialogue and softer sounds will sound quiet, and louder sounds will be about the same level as your other videos. AC3 filter is fine for playback on your PC, but if you want to change the levels for encoding to DVD you will have to demux the audio back to mono wavs, increase the gain on each one, then re-encode.

Anyone know how to do this, please help me!!!

[adam]

Wile_E, I somehow lost track of this thread...

No normalizing does not work the same as dynamic range compression. Normalization raises or lowers the overall amplitude to the selected point. By normalizing multiple sources to a standard number that will make all of their highest peaks the same amplitude. Everything else will be adjusted proportionally.

Dynamic range compression actually lowers your peaks and raises your valleys. BeSweet (gui for Azid) has a boost option for this. Other than that, there are all kinds of commercial and free DX compression filters.

voxi: Besweet will let you demux an AC3 file to 6 waves. Then use whatever AC3 encoder you want and just set a positive gain...most encoders should have this option.

But its not clear whether you are doing the same thing as the original poster. If the volume of the entire audio track is too low then you simply want to increase the gain when you encode back to AC3. But if you are experiencing the problem where volume is too low and explosions and such are too loud, then you want to use compression as you encode back to AC3.

[paulw]

I use Canopus Procoder 1.5 to convert many AC3 AVI to DVD. I can simply up the levels in AC3 Filter before running Procoder and they come out with greater levels in my MPEG2 files. No demux etc required. It also means that when watching with WMP or such I dont have to move the volume knob to 11.

Thanx for the tip. It sure sorted out one issue that i have had with AC3 files

[slacker]

I know AC3 is the end all around here, but in all honesty for the average home videophile it is a royal pain in the ars to work with. Frankly, I would rather take the storage HIT and encode my dvds using lpcm. A lot less trouble.

[non-linear]

I know AC3 is the end all around here, but in all honesty for the average home videophile it is a royal pain in the ars to work with. Frankly, I would rather take the storage HIT and encode my dvds using lpcm. A lot less trouble.

Personally, I've been using AC3 for 2 years and have never once considered compression. What I do is load my audio in Adobe Audition, normalize to 0dB, then use ffmpeggui to make the audio to AC3. That's it, and it works just fine.

[slacker]

non-linear,

No one around here seems to have a problem with their encodes. This is true! However, when I compare my LPCM encodes to my AC-3 encodes they WORK, but I they are distinctly dissimilar, even using several different settings for Line Mode and Dialog Normalization.

Based on other discussions, I'm pretty sure I need Sound Forge's ability to document LAeq and RMS levels. With those values, you can match your AC-3 to LPCM almost to the tee. Otherwise, you're shooting in the dark as far as accuracy goes.

[daphy]

nzjacob wrote:
I use Canopus Procoder 1.5 to convert many AC3 AVI to DVD. I can simply up the levels in AC3 Filter before running Procoder and they come out with greater levels in my MPEG2 files. No demux etc required. It also means that when watching with WMP or such I dont have to move the volume knob to 11.

AFAIK Canopus Procoder doesn´t include an AC3 encoder, so my question is, what kind of audio stream will be created while encoding this AVI?
If no demuxing/new encoding took place, why is that track diffrent from its source?
The only thing I could imagine is, that the dynamic flag was changed in the header of the AC3 file - but this can´t depend on a knob inside AC3filter, am I right?

So PLZ check the MPEG2´s audio track THX!

CYA Daphy

[fritzi93]

To clarify my previous post: Configure AC3Filter, extract ac3 with VirtualDubMod, encode m2v (with TMPGEnc, in my case) , and author. That was my method, IIRC, my point being I never re-encoded ac3 or otherwise monkeyed with it. The only operation on the audio was the extraction of a new ac3 file after configuring AC3Filter. The audio levels in the authored DVDs were fine.

[hiptune]

AC3 has a wider dynamic range than PCM audio (or mp3 audio etc)

AC3 has nothing wider than PCM audio. PCM has everything over AC3. And let's not even bring in MP3 and mention it is the same breath as PCM or AC3.

guns1inger, where did you read this?