KVR Audio

Lagrange · Post by **Lagrange** » Tue Jul 18, 2006 10:03 am

Is there such an effect that I could put 'lets say' noisy high end keyboards through and would take out some or all of the aliasing?? What would be the difficulties in developing a plug like this??

C

jupiter8 · Post by **jupiter8** » Tue Jul 18, 2006 10:11 am

The problem is deciding what is aliasing and what is not.You simply cannot remove aliasing after it's been produced.
And what has noisy to do with aliasing? Either you've misunderstood something or i did.

DevonB · Post by **DevonB** » Tue Jul 18, 2006 10:28 am

Yes. Increase your sample rate to 96k or 192k. That will most likely kill the aliasing for the instrument you're playing that aliases. If you're trying to remove after the fact, you're screwed. If it's on a piece of external hardware, you're screwed.

Devon

arguru · Post by **arguru** » Tue Jul 18, 2006 10:53 am

edit: and nothing more to add, the two above replies are 100% clear already.

Christian Budde · Post by **Christian Budde** » Tue Jul 18, 2006 10:54 am

I've once developed a plugin, which operates as bridge. If you open it, it promts for another plugin which then runs oversampled (higher samplerate).
I've implemented the technology in my WinAmp VST Bridge. Unfortunately the original VST plugin got lost, so I'd have to rewrite it again. Anyway, it worked pretty good.
Christian

Lagrange · Post by **Lagrange** » Tue Jul 18, 2006 10:58 am

Christian: I would be very interested in this 1!!

People please confuse yourself, have your morning coffee and think about what I'm asking before answering.. I think that aliasing can be interpreted as a form of noise between the actual sound.. Expand your though process for just a minute.. Heres an example from JXsynth..

low quality anti-aliasing

Hi quailty anti-aliasing

again..
LQA-A

HQA-A

1 more..
L

H

I can 'for instance' open a played keyboard part in Adobe Audition select the 'aliasing' audio and delete it basically making it look like the same Hi Quality Anti-Aliasing image.. Do not allow the technical aspect get in the way here.. Let me know what youz think..

Lagrange · Post by **Lagrange** » Tue Jul 18, 2006 11:05 am

shit sorry gotta have my coffee.. little grumpy for a minute..

C

kmonkey · Post by **kmonkey** » Tue Jul 18, 2006 11:17 am

I like aliasing sometimes. Can be useful from time to time. Depend on what i am working and tryin to get.

BertKoor · Post by **BertKoor** » Tue Jul 18, 2006 11:18 am

Lagrange wrote:Is there such an effect that I could put 'lets say' noisy high end keyboards through and would take out some or all of the aliasing??

Is this "noisy high-end keyboard" hardware or software? If it's software, then an oversampling plugin like Christian's would work, since this cures it at the source. With hardware you're kinda out of luck.

Is it really aliasing noise? Isn't it general background white noise? Very different things...

Lagrange wrote:I think that aliasing can be interpreted as a form of noise between the actual sound..

Not all harmonic content that's faint is aliasing. Aliasing noise is introduced when samples are played back at another sampling rate using inferior resampling algorythms. When the synth is silent, there is no noise at all.

Background noise is in the signal all the time, and comes from inferior cirquits (opamps, filters, whatever) used in the hardware.

Lagrange wrote:I can 'for instance' open a played keyboard part in Adobe Audition select the 'aliasing' audio and delete it basically making it look like the same Hi Quality Anti-Aliasing image..

Sure you can erase any spectrum content you don't like. With that approach YOU are deciding what's aliasing and what's not, making intelligent decisions. Software isn't that far. Yet.

It is possible to have a plugin do FFT analysis on a signal, and only allow the strongest harmonical contents to pass. Should work OK on synths modelled like analog synths: VCO with square wave, followed by a filter and amp. With anything more complex you will definitely loose the contents that define the character of the sound. Subtilities that are supposed to be there. Throw away the baby with the bathwater as we say here...

If you really want to fix aliasing and nothing else, it should be fixed inside the originating synth. Fooling the bad-behaving synth to perform at a higher sample rate will move the aliasing sounds up by one or two octaves so it can be filtered out by a proper resampling algorythm with good anti-aliasing.

dreamkeeper · Post by **dreamkeeper** » Tue Jul 18, 2006 11:31 am

Lagrange wrote:
I can 'for instance' open a played keyboard part in Adobe Audition select the 'aliasing' audio and delete it basically making it look like the same Hi Quality Anti-Aliasing image..

Maybe. Though you won't be able to do that without knowing how the non-aliased signal looks like. That's the point: once aliasing has occured, it's integral part of the signal. There's no special "signature" to it, hence it's impossible to decide which is aliasing and should be removed and which is the desired signal.

If I'm not mistaken, those spectrums you posted, are mostly showing sidebands. Those are produced by audio-rate modulation techniques like FM, PM, RM etc. AND are desired to produce the timbres you're after by using these synthesis methods in the first place. They are NOT aliasing!

Aliasing occures when, due to modulation/processing, harmonics are generated that cannot be represented at the current samplerate. Those frequencies then "fold back" into the representable range, most likely into the audible range as well.

The only way to reduce (not even totally remove) this is oversampling, which is what Christian is talking about. That way, the higher (inaudible) harmonics can be calculated correctly (although only up to a certain point, which depends on the samplerate) and filtered out. Then the signal gets downsampled again.

Hope that makes some sense.

werner

Lagrange · Post by **Lagrange** » Tue Jul 18, 2006 11:37 am

Sure you can erase any spectrum content you don't like. With that approach YOU are deciding what's aliasing and what's not, making intelligent decisions. Software isn't that far. Yet.

This makes much more sense.. which leads me to..

It is possible to have a plugin do FFT analysis on a signal, and only allow the strongest harmonical contents to pass.

Which plugin would that be?? I guess this is what I'm looking for (possible setup or single plugin)

Thanks for the reps on this.. I know it's a touchy subject when people are talking about inferior algos and circuitry cause theres a possiblity that the quality of some synths will come into question.. Thats not my intention just looking for a solution to a problem..

C

Lagrange · Post by **Lagrange** » Tue Jul 18, 2006 11:43 am

dreamkeeper: Yes that makes more sense.. So these guys dont know what there talking about??

http://www.jxplugins.co.uk/index.php3?p=5

Let me put the question this way.. Is there a plugin that would take me from this:

to this

Sorry but this is extremely important for me..

C

kmonkey · Post by **kmonkey** » Tue Jul 18, 2006 11:45 am

reNovator

jupiter8 · Post by **jupiter8** » Tue Jul 18, 2006 11:49 am

The JXSynth site talks about preventing aliasing from happening. Not how you remove it once it is there.
'Cause you can't.

Lagrange · Post by **Lagrange** » Tue Jul 18, 2006 11:49 am

reNovator?? (Aww man I knew I should not have said that I could cut out the audio myself..) Do I have to use reNovator manually or can I apply it to 'lets say' a solo part from a synth??

Anti-Aliasing plugin