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  1. Is there a way to normalize AC3 audio without re-encoding? I know this is possible with MP3. I'm curious because I'm trying to make a DVD with varying clips but each video has a different volume. I'd like them all to have the same volume without re-encoding, if possible.
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  2. AC3 Normalizer was the closest thing I could find to what I wanted so far but it re-encodes the audio. The huge deal breaker is that the results produced major buzzing noises and crackling.
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  3. I'm a Super Moderator johns0's Avatar
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    I use audacity with ffmeg plugin to normalize ac3,never get any buzzing or crackling that wasn't there.It re-encodes but does a good job.
    I think,therefore i am a hamster.
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    I rememmber playing with this a year or two back, I used Audacity to WAV, then the Aften Gui back to ac3.

    It allows you to add Dialnorm and/or set optional dynamic compression
    Last edited by davexnet; 27th Jul 2022 at 16:59.
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  5. If there is a way to losslessly do this with MP2 maybe I'll consider that.
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  6. https://forum.audacityteam.org/viewtopic.php?t=104273
    DVD Doug - If you don't know this already - Normalizing files doesn't necessarily make them all sound equally-loud.
    Is there a program that can do this or is this something that has to be done manually?

    Also I tried this and it did it's job. https://forum.videohelp.com/threads/258002-Mini-How-To-Increase-Your-AC3-Volume
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  7. I'm a Super Moderator johns0's Avatar
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    Unless you have the best audio system in the world you won't hear any difference when you properly encode ac3 with the same bitrate or higher.Also audacity will save the file as ac3 so no need for wav and then ac3 encoding.
    I think,therefore i am a hamster.
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  8. Originally Posted by johns0 View Post
    Unless you have the best audio system in the world you won't hear any difference when you properly encode ac3 with the same bitrate or higher.Also audacity will save the file as ac3 so no need for wav and then ac3 encoding.
    I encoded one 192kbps ffmpeg AC3 file. Then I transcoded that one using the same settings and compared the two in a blind test. I'm no audiophile but I could tell the difference between the two. I don't have any set up either I'm just using airpods. I know ffmpeg isn't a good codec so I'll try one with aften too.

    In the grand scheme of things it doesn't matter a ton, but I want to make a DVD with music so I'm trying to avoid re-encoding a bit.


    foo_abx 2.0.6d report
    foobar2000 v1.6.7
    2022-07-27 20:53:57

    File A: 192.wav
    SHA1: d42410b08e49be8063744f3d08dbfca3ae455a90
    File B: 192 transcode.wav
    SHA1: 77ed3584f1cf96e9821c2067c5282aad6e1ad1e9

    Output:
    Default : Primary Sound Driver
    Crossfading: NO

    20:53:57 : Test started.
    20:56:20 : 01/01
    20:58:53 : 02/02
    20:59:12 : 03/03
    21:00:19 : 04/04
    21:00:32 : 05/05
    21:00:44 : 06/06
    21:00:55 : 07/07
    21:01:15 : 08/08
    21:01:29 : 09/09
    21:01:41 : 10/10
    21:01:41 : Test finished.

    ----------
    Total: 10/10
    p-value: 0.001 (0.1%)

    -- signature --
    40d80805ef6e8eddd02269922a1f972c7209354d
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  9. Here's 256kbps aften. This test was way harder and I took breaks.


    foo_abx 2.0.6d report
    foobar2000 v1.6.7
    2022-07-27 21:35:01

    File A: 256.wav
    SHA1: df919e9e3a15b561f0ae57a736626a03889b4a38
    File B: 256 transcode.wav
    SHA1: 66e71008842b2cec0a91a37d2f2838d59db3bdc2

    Output:
    Default : Primary Sound Driver
    Crossfading: NO

    21:35:01 : Test started.
    21:35:46 : 01/01
    21:45:09 : 02/02
    21:46:10 : 02/03
    21:47:38 : 03/04
    21:48:11 : 04/05
    21:49:05 : 05/06
    21:51:16 : 06/07
    21:51:51 : 07/08
    21:52:08 : 08/09
    21:52:25 : 09/10
    21:52:25 : Test finished.

    ----------
    Total: 9/10
    p-value: 0.0107 (1.07%)

    -- signature --
    cbd14b52f93a5ba85136e4fe5789932a64ac8e83
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    Never used that tool. Are you saying the Aften encode sounded closer to the original than the Audacity encode?
    If that's so, use Aften.
    You have to re-encode regardless, there doesn't seem to be any other way.
    Even changing or nullifying Dialnorm requires a re-encode
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  11. I'm a Super Moderator johns0's Avatar
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    Not sure what settings you used but i did a test of one ac3 and re-encoded to the same bitrate with audacty and no other settings changed and it sounded exactly the same through my high quality headphones.
    I think,therefore i am a hamster.
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  12. For ffmpeg
    -ab 192k

    For aften
    -b 256
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  13. Member
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    Originally Posted by shampistols69 View Post
    Still involves re-encoding. If you have a point to make, speak up
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  14. I think that is the best and easiest way to do it but involves re-encoding.
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  15. I'm a Super Moderator johns0's Avatar
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    When you said 'I know ffmpeg isn't a good codec ' just proves you dont know anything about encoding.
    I think,therefore i am a hamster.
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  16. Member Skiller's Avatar
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    There is ChangeDN which changes the DialNorm value present in any AC3. This works without re-encoding but is not exactly normalization in the usual way. And if the value of DialNorm is already -31 db, it cannot be made any louder with this.

    Note that this should not be done to 5.1 mixes that may use DRC during playback.
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  17. shampistols69,
    ffmpeg's ac3 encoder is Aften. It was incorporated into ffmpeg a long time ago, I think after the Aften author stopped developing it.

    A sample Aften command line for foobar2000:

    -readtoeof 1 -pad 0 -v 0 -b 192 - %d

    ffmpeg:

    -i - -ignore_length true -c:a ac3 -b:a 192k %d

    Are you aware foobar2000 has a ReplayGain scanner, so you can scan the files, save the info to tags, then apply the ReplayGain info to adjust each file's volume while converting?
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  18. I am aware of foobar's tag scanner but the audio is for DVDs.
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