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Alaising...er, what is it?

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Alaising...er, what is it?

Postby russianpolecat » Fri Jan 16, 2015 12:34 pm

Hey - as subject heading. Can somebody please explain to me (in simple terms :D) what aliasing is? I've seen it mentioned on these forums, and I know it's got something to do with the sampling process/nasty artifacts and what not, but I don't really 'get it' as yet. It seems to be related to sample rate conversion?

Thanks! :)

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Re: Alaising...er, what is it?

Postby david1103 » Fri Jan 16, 2015 12:59 pm

Non technical summary:

Usually analog distortion is related to the note played on a musical instrument, it can sound good.

Aliasing is a biproduct of digital signal processing at lower sample rates. It is NOT related to the note played and sounds horrible. It is disharmonic.

Often it is present in VST, but at such a low level you won't hear it. Sometimes it is loud enough to cause a problem. In Nebula it is not usually a problem at all, it can easily be measured using a a spectrum analyser.

Basically, if you can hear a nasty type of distortion in a VST and it sounds 'digital' it is probably aliasing. Run the same VST at 96k and if it goes away then it definitely is!

Hope that helps :)
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Re: Alaising...er, what is it?

Postby himhui » Fri Jan 16, 2015 1:07 pm

Last edited by himhui on Sun Mar 29, 2015 6:21 pm, edited 1 time in total.
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Re: Alaising...er, what is it?

Postby russianpolecat » Fri Jan 16, 2015 3:28 pm

Cheers guys. Maybe this is more of a problem for the Acqua plugs then?
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Re: Alaising...er, what is it?

Postby Sheikyearbouti » Fri Jan 16, 2015 3:54 pm

It is genrally a non-harmonic digital distortion that can be caused because of many reasons - bad analogue to digital conversion (all standard converters have some aliasing), various other digital operations like sample rate conversion, or even clipping (yes, clipping digitally also creates aliasing). The big thing you should worry about is to not clip your audio really.

If you want ot know more, and in depth, I strongly recommend a book by Nika Aldrich 'Digital Audio Explained for the audio engineer'. The guys know his shit and explains it all in a very understandable language.
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Re: Alaising...er, what is it?

Postby Sheikyearbouti » Fri Jan 16, 2015 4:01 pm

russianpolecat wrote:Cheers guys. Maybe this is more of a problem for the Acqua plugs then?

Not really. From the measurements I've seen all current Acquas preform remarkably good when it comes to aliasing.
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Re: Alaising...er, what is it?

Postby russianpolecat » Fri Jan 16, 2015 6:02 pm

Sheikyearbouti wrote:
russianpolecat wrote:Cheers guys. Maybe this is more of a problem for the Acqua plugs then?

Not really. From the measurements I've seen all current Acquas preform remarkably good when it comes to aliasing.
That's good to hear ;). I thought perhaps because of the SRC, or perhaps Acqua's deal with that differently? I only have the free Red EQ so far Acqua wise (which is great by the way) but whenever I change sample rate from 44 to 96 or vice versa the Red EQ loads up as normal...you don't have to choose a specific instance as with Nebula.
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Re: Alaising...er, what is it?

Postby Support » Fri Jan 16, 2015 8:28 pm

russianpolecat wrote:
Sheikyearbouti wrote:
russianpolecat wrote:Cheers guys. Maybe this is more of a problem for the Acqua plugs then?

Not really. From the measurements I've seen all current Acquas preform remarkably good when it comes to aliasing.
That's good to hear ;). I thought perhaps because of the SRC, or perhaps Acqua's deal with that differently? I only have the free Red EQ so far Acqua wise (which is great by the way) but whenever I change sample rate from 44 to 96 or vice versa the Red EQ loads up as normal...you don't have to choose a specific instance as with Nebula.


Due old version try to load vectors at saved sample rate and not at the current one so you get a not correct sample rate conversion. We change this behavior in new RC and betas and there is a tag for force to work in old mode.

Should be good to know that is the idea behind to change old sessions sample rate.
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Re: Alaising...er, what is it?

Postby russianpolecat » Sat Jan 17, 2015 12:30 am

Cool, that's great :)
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Re: Alaising...er, what is it?

Postby Sheikyearbouti » Sat Jan 17, 2015 3:58 am

Ah, you mean non-native... the SRC algo matters.
These are quite fun to look at:
http://src.infinitewave.ca/
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