Low Volume in encoded AC3

[King_Diamond]

Hello everyone,

I spent a whole day searching this forum about low volume in ac3 audio. There are so many threads about this issue, but I did not manage to find a solution to my problem, unless, if I understood correctly from other threads, that ac3 is normally low volumed.

My problem is this. I am doing a dvd with audio being totally music. I made a 6 channel audio and encoded it to ac3 format. The problem is that I cannot increase the volume before I encode it since the sound is already just under 0db and if I exceed 0db, it will start clipping.

There are so many experts in this forum about this subject that I was hoping that someone can help me figure this out, perhaps by setting the correct settings in the ac3 encoder. These are the present settings I'm using :

DRC -> None
Bitstream -> ME
BSI - Center and Surround -> -3db
Surround 90 Degree Phase Shift -> On
Surround 3db Attenuation -> On
Digital de-emphasis -> On
DC high pass filter -> On
Bandwidth low pass filter -> On
LFE low pass filter -> On

Any suggestions would be much appreciated.

[digitalvideo]

Do you have acces to the dial norm level, normaly -27db ?

Put it to 0 db and you have full scale or maybe -31, make the test

[tebasuna51]

If you have the uncompressed source (wav) near 0 dB and you want the ac3 at same volume than the wav modify:

Surround 3db Attenuation -> Off
Digital de-emphasis -> Off

and don't forget the important:

Dialog normalization -> 31 (-31 dB)

The couple DRC=None, DialNorm=31 is not Dolby compliant but guarantee the same volume wav-ac3. If you don't obtain the same volume is a player problem, check the player config.

[King_Diamond]

Some time ago, I read that using bitstream ME, a dialog channel is not present. Infact, I tried setting dialnorm at -31, -27 and -1 (my encoder does not allow 0) and there was no hearable effect. I will try setting the two options highlighted by tebasuna51 to off and post back.

[tebasuna51]

Some time ago, I read that using bitstream ME, a dialog channel is not present.
I don't know, I always use 'Complete Main' instead 'Music and effects'

[digitalvideo]

normally all dolby encoder have the Dialog normalization parameter, may be you have to look in meta data.

It's a paramater that explain to the decoder how to apply a sort of volume filter. -31 is the value for no filter !!

[King_Diamond]

tebasuna51,

I tried the settings highlighted by you and also tried various bistream modes but still same volume level. I also tried applying different dialnorm settings but again, no difference in volume level.

digitalvideo,

Perhaps I wasn't clear. The dialnorm option is present but from what I read, any setting in bitstream ME, it does not make any difference since no dialog is present. Infact I also tried setting dialnorm to different levels ME bitstream but I could not hear any difference.

[tebasuna51]

Perhaps I wasn't clear. The dialnorm option is present but from what I read, any setting in bitstream ME, it does not make any difference since no dialog is present. Infact I also tried setting dialnorm to different levels ME bitstream but I could not hear any difference.
What is your encoder?
What is your player for ac3 and wav?

[King_Diamond]

I'm using the encoder within Premiere Pro.

As regards the player, I'm using WMP with AC3 Filter and dvd set top player.

[tebasuna51]

AFAIK Premiere use the SurCode plugin. Is ok.

To compare volume between wav source and ac3 output you need use the same filter to play, then go to System tab in Ac3 Filter Config and check Use Ac3 Filter for...
- PCM
- AC3
at least.

Now play the wav, after the ac3, and see the input levels in Main tab of AC3 Filter Config.

[King_Diamond]

I tried your suggestion but there is no activity in the input level. I checked the properties of WMP and audio codec is set to AC3 Filter. Am I doing something wrong?

[tebasuna51]

If you open the AC3 Filter Config out off WMP is other instance, must be open from inside WMP (but I don't know how because I don't use WMP).

The method most sure is using GraphEdit.

[King_Diamond]

Ok I downloaded GraphEdit and the input levels of the AC3 file are roughly an average of -25db, peak roughly at -10db. The wav file levels are roughly an average of -10db, peak roughly at -2db.

[tebasuna51]

Ok I downloaded GraphEdit and the input levels of the AC3 file are roughly an average of -25db, peak roughly at -10db. The wav file levels are roughly an average of -10db, peak roughly at -2db.

Well, you are right.

Maybe the Premiere encoder is the problem.
Try with Aften (http://kurtnoise.free.fr/index.php?dir=Aften/)

[King_Diamond]

I can't run Aften. As soon as I click encode, it immediately says Output finished successfully but no file is encoded.

[tebasuna51]

You need the command line aften.exe and AftenGUI, then encode the 6channel wav.

[King_Diamond]

I have the command line, perhaps i'm doing something wrong. I will try again.

In the meantime, I added gain to the AC3 file using AC3Machine. I haven't tested it yet but what's strange is that the file size is exactly half of the original file. Is this normal?

[tebasuna51]

In the meantime, I added gain to the AC3 file using AC3Machine. I haven't tested it yet but what's strange is that the file size is exactly half of the original file. Is this normal?
The filesize is determined by time length and bitrate. If is half you use half bitrate.
BTW you can't add gain with AC3Machine, you can distort the signal and the max output value is always half of Aften/Surcode/SoftEncode output value. AC3Machine is obsolete because can't use Aften (and others problems), use BeLight instead.

[King_Diamond]

A friend of mine has one of the software you mentioned, namely Soft Encode. So I took the source wav and encoded it on his pc. The result was the same low volume. Hence I'm getting to believe that it's not a problem with my encoder but perhaps it's something else.

As for AC3Machine, it's the only software I know that can gain volume of an AC3 file. I didn't have the time to test it yet but if you're saying that it distorts the signal, it can't be good as an alternative solution.

[tebasuna51]

Sorry, but this:
Ok I downloaded GraphEdit and the input levels of the AC3 file are roughly an average of -25db, peak roughly at -10db. The wav file levels are roughly an average of -10db, peak roughly at -2db.
is not possible using SoftEncode or Aften.

Maybe if you can send ( http://www.mytempdir.com/ ) a little fragment of source wav and ac3 encode, I can test it.

[tetrisds]

I had a really good read on this, very detail,
and very useful information.Thanks.

[tebasuna51]

@King_Diamond
Received yours test by PM. The AC3 volume is the same than WAV, I use SoundOut (http://forum.doom9.org/showthread.php?t=120025) (AviSynh plugin) -> Analyze Sound utility with these .avs:
BassAudioSource("g:\test.wav") #because WAVE_FORMAT_EXTENSIBLE header
SoundOut()
And:
NicAc3Source("g:\test.ac3", DRC=0) #without Dynamic Range Compression to obtain the full volume
SoundOut()
And the results:

Analyzed 100%. TEST.WAV ------------------------------------------------

[Ch 0] Maximum:-5.98dB. Average:-25.35dB. RMS:-20.99dB. ReplayGain: 3.11dB
[Ch 1] Maximum:-5.98dB. Average:-25.35dB. RMS:-20.99dB. ReplayGain: 3.11dB
[Ch 2] Maximum:-3.34dB. Average:-26.52dB. RMS:-20.93dB. ReplayGain: 7.15dB
[Ch 3] Maximum:-1.10dB. Average:-27.20dB. RMS:-19.05dB. ReplayGain:11.67dB
[Ch 4] Maximum:-4.14dB. Average:-26.96dB. RMS:-21.72dB. ReplayGain: 6.74dB
[Ch 5] Maximum:-4.14dB. Average:-26.96dB. RMS:-21.72dB. ReplayGain: 6.74dB

[All channels] Maximum:-1.10dB. Average:-26.36dB. RMS:-20.80dB

Analyzed 100%. TEST.AC3 ------------------------------------------------

[Ch 0] Maximum:-5.61dB. Average:-25.46dB. RMS:-21.10dB. ReplayGain: 3.27dB
[Ch 1] Maximum:-5.60dB. Average:-25.46dB. RMS:-21.10dB. ReplayGain: 3.27dB
[Ch 2] Maximum:-3.17dB. Average:-26.64dB. RMS:-21.05dB. ReplayGain: 7.24dB
[Ch 3] Maximum:-1.37dB. Average:-27.44dB. RMS:-19.31dB. ReplayGain:11.75dB
[Ch 4] Maximum:-6.91dB. Average:-30.28dB. RMS:-25.18dB. ReplayGain: 9.87dB
[Ch 5] Maximum:-6.95dB. Average:-30.28dB. RMS:-25.18dB. ReplayGain: 9.87dB

[All channels] Maximum:-1.37dB. Average:-27.37dB. RMS:-21.63dB

Played with GraphEdit and Ac3 Filter (or ffdshow) the levels are equivalents.

You need re-check your players configuration because the ac3 is ok, difference less than -1 dB in RMS, peaks at -1.37 dB ...

The standalone players have also something to configure: the Dynamic Range Compression (DRC)
If you have DRC properly configured (to equalize the sound the high volume are attenuated and the global volume is down) and for you is still too low in volume maybe you need read:

The Loudness War (http://forum.doom9.org/showthread.php?t=120637)

You can apply to the wav any boost filter if you want, but the problem is not related with the ac3 format or the ac3 encoder.

[King_Diamond]

Thanks for your detailed reply. Unfortunately I don't know how to use avisynth but I will give it a try when I have some free time.

You explained that I should check DRC of standalone player. I actually don't know how to do this but since I used no DRC in encoding, would this make a difference?

I visited the link about loudness war. It's very interesting and it is very true than on increasing loudness, you can loose some frequencies. However there is another issue which is not highlighted. The more you turn up the volume, the more the hiss increases. I actually don't like hiss noise, it reminds me of the old LPs.

Since your tests proved that the ac3 file is ok, is there anything else I can do apart from applying a boost filter? I guess this would clip the ac3 file.

[Taurus]

I tried your suggestion but there is no activity in the input level. I checked the properties of WMP and audio codec is set to AC3 Filter. Am I doing something wrong?
First I've got to say, I've never had problems playing back AC3 files.
If there are any low level encodes, normally AC3 Filter will fix it for me:p
So why don't you give another player/decoder a chance.
At this time I'm using MediaPlayerClassic and AC3Filter1.30b
and it works.
What makes me wonder: First you wrote about PC playback via WMP/AC3Filter, but in your last post about standalone players DRC.
I think tebasuna51 was referring to DRC in AC3Filter configuration.
Which version of AC3Filter is installed on your side?
......and Aften is a pretty good encoder.......
And with a Gui there should be no problems even for commandline dyslexic :)

Taurus

[King_Diamond]

Thanks for your reply Taurus.


What makes me wonder: First you wrote about PC playback via WMP/AC3Filter, but in your last post about standalone players DRC.

I'm actually building a dvd project and hence I'm using pc to edit and encode but the final product will be on a dvd disc to be played on a standalone player.


If there are any low level encodes, normally AC3 Filter will fix it for me

AC3 Filter can fix it if it is played through pc but not for the encoded AC3 file to be used on dvd.


So why don't you give another player/decoder a chance.

As stated earlier, I tried various players, encoders, decoders like WMP, GraphEdit, AC3Filter, Soft Encode, AC3Machine, etc. but with same results. I don't know what else to try.

[King_Diamond]

From the tests performed by tebasuna51, I was wondering whether there's any free AC3 software that can increase rms but leaves peak levels as they are. I would like to give it a try.

[King_Diamond]

I finally managed to test the ac3 file encoded with AC3Machine and it did the job. It gained volume and no clipping. The sound is not good for my taste but I guess it's my fault since I added a gain of 15db. Now I'm trying BeLight as suggested by tebasuna51 but I'm not sure which Endian to use. I heard about Intel byte order but never heard of motorola.

Can anyone explain the difference between these two please?

[tebasuna51]

I heard about Intel byte order but never heard of motorola.

Can anyone explain the difference between these two please?
Don't use AC3enc, the volume is half (-6 dB) than with Aften.

Forget the difference about Intel byte order and motorola (ac3 standard use Motorola).

[King_Diamond]

I tried gaining volume with BeLight and it clips. I'm going to take your suggestion and leave it as it is. Hope I don't get much complaints!

Thanks a lot tebasuna51.