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Old 27th January 2009, 20:00   #1  |  Link
loekverhees
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Surround AAC to Stereo

I've an audio source (from a movie) in the AAC format which is surround. I've encoded it into a stereo wave file with dBpoweramp Music Converter. However, the vocals in the audio are often very quietly in comparison with the music. Maybe dBpoweramp just took the Front left and Front right channels and didn't include the Center channel, but I'm not sure about this. Does someone know how to make the voices in the audio as loud as the music? When I play back the movie with the original surround audio, the volume of the vocals are fine, but I really want it to be stereo.
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Old 28th January 2009, 01:27   #2  |  Link
tebasuna51
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Try other conversion method: Faad, Foobar2000, BeHappy, ...
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Old 28th January 2009, 06:28   #3  |  Link
Blue_MiSfit
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You could try eac3to.

Simply feed it the original source (AC3, guessing?), and specify 2 channel AAC like this:

Code:
eac3to input.ac3 -down2 output.aac
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Old 28th January 2009, 12:22   #4  |  Link
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@Blue_MiSfit, the source is AAC, eac3to can decode AAC only with Nero installed
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Old 28th January 2009, 19:16   #5  |  Link
loekverhees
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Thanks for your answers. I tried with dBpoweramp, Foobar2000 and BeHappy. After this, I created one sample of 20 seconds of each in Adobe Audition and normalized them (100%). Then I compared them and actually found them to be all exact the same! Is there a way to manually 'put more Center channel in the downmix equation'?
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Old 29th January 2009, 00:39   #6  |  Link
tebasuna51
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Quote:
Originally Posted by loekverhees View Post
Thanks for your answers. I tried with dBpoweramp, Foobar2000 and BeHappy. After this, I created one sample of 20 seconds of each in Adobe Audition and normalized them (100%). Then I compared them and actually found them to be all exact the same! Is there a way to manually 'put more Center channel in the downmix equation'?
If you use BeHappy with the stereo downmix you can Export AviSynth Script instead Enqueue and modify (with Notepad or other text editor) the mix coeficients:
Code:
# Simple Stereo
function fx(clip a) {
flr = GetChannel(a, 1, 2)
fcc = GetChannel(a, 3)
lfe = GetChannel(a, 4)
lfc = MixAudio(fcc, lfe, 0.2071, 0.2071)
mix = MergeChannels(lfc, lfc)
lrc = MixAudio(flr, mix, 0.2929, 1.0)
blr = GetChannel(a, 5, 6)
return MixAudio(lrc, blr, 1.0, 0.2929)
}
The black is the Center channel and you can increase the value but the 4 coeficients must sum 1.0. Maybe you can decrease the lfe and/or blr (back left-right)

After you can open in BeHappy the edited avs. Don't use any DSP (they are included in avs) and encode
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Last edited by tebasuna51; 29th January 2009 at 00:42.
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Old 29th January 2009, 18:43   #7  |  Link
loekverhees
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Thanks! I edited the avs file, see below:

Code:
# Simple Stereo
function f3d6248d36198448f8d4a086df5d345c0(clip a) {
flr = GetChannel(a, 1, 2)
fcc = GetChannel(a, 3)
lfe = GetChannel(a, 4)
lfc = MixAudio(fcc, lfe, 0.46, 0.12)
mix = MergeChannels(lfc, lfc)
lrc = MixAudio(flr, mix, 0.26, 1.0)
blr = GetChannel(a, 5, 6)
return MixAudio(lrc, blr, 1.0, 0.16)
}
Now, the spoken voices are much better .

BTW, When I convert the wave-file to AC3, should the AC3 be 16 bits, 24 bits or 32 bits in order to make a VIDEO-DVD?

Last edited by loekverhees; 29th January 2009 at 19:11.
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Old 28th January 2009, 18:23   #8  |  Link
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you can try to decode the .aac with neroaacdec.exe (neroaacdec.exe -if audio.aac -of audio.wav)
i am not sure if it has support for raw .aac but if it has not you can mux the .aac to .mp4 with (mp4box.exe or mp4creator.exe) and it works for sure (neroaacdec.exe -if audio.mp4 -of audio.wav)
now you have a mutichannel .wav that can be properly downmixed to stereo with various tools (behappy)...
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Old 28th January 2009, 20:17   #9  |  Link
b66pak
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how many channels have the original .aac?
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Old 28th January 2009, 20:48   #10  |  Link
loekverhees
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My original AAC file has 6 channels (5 + subwoofer I think).
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Old 28th January 2009, 21:04   #11  |  Link
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Ah. Gotcha

I misunderstood.

You could simply use foobar2000, and add its 5.1->2ch downmix DSP plugin.

~MiSfit
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Old 29th January 2009, 21:51   #12  |  Link
Blue_MiSfit
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Doesn't matter. AC3 doesn't really think in terms of bit-depth

~MiSfit
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Old 29th January 2009, 22:25   #13  |  Link
loekverhees
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Quote:
Originally Posted by Blue_MiSfit View Post
Doesn't matter. AC3 doesn't really think in terms of bit-depth

~MiSfit
Ok, thanx !
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