visual dither test

[vieris]

so i've been wondering how different dithers effect audio. so i did some tests.. i made a track with 24bit white noise at -80 with a fade to nothing. i exported the file with all different types of dither and lack of dither. i then made a session imported all the exported files and normalized them to see what happened visually.. the results are pretty cool.. i'm still wondering about dithering from 32 to 24.. i think the dither might ad more noise then it would gain..

http://www.rhythminmind.net/temp/dither/24.gif

http://www.rhythminmind.net/temp/dither/32.gif

[image]http://www.rhythminmind.net/temp/dither/24.gif[/image]

[image]http://www.rhythminmind.net/temp/dither/32.gif[/image]

[Ryan Young]

That's really awesome! Thanks for doing those. I'm going through my Pro Tools cert right now and went over all the different reasons you'd use dither, this helped me understand it a lot more.

[vieris]

no prob.. noise shaping is the way to go.... POWR #3 is my fav... noise shaping puts the dither noise in highend frequencies out of human range.. my visuals dont show what frequencies are going on but it's kinda cool to see anyway..

[vieris]

I would like to get your guys opinions on dithering from 32 to 24... i have 2 types i'm dealing with. edited 32 bit tracks i want to export to 24bit and unedited 32 bit tracks. all recorded with 24bit hardware.. i'm under the impression that with the unedited tracks can just trash the extra bits.

[feedback]

[deleted]

[Nika]

so i've been wondering how different dithers effect audio. so i did some tests.. i made a track with 24bit white noise at -80 with a fade to nothing. i exported the file with all different types of dither and lack of dither. i then made a session imported all the exported files and normalized them to see what happened visually.. the results are pretty cool.. i'm still wondering about dithering from 32 to 24.. i think the dither might ad more noise then it would gain..

http://www.rhythminmind.net/temp/dither/24.gif

http://www.rhythminmind.net/temp/dither/32.gif

Crikey! What are you intending to show? The ear doesn't hear like you are demonstrating this on the screen - we don't hear linear samples in this way. We hear sort of a windowed FFT of the waveform. In order to "look" at the effectiveness of various dither types you really need to take these various signals and run them into an FFT analyzer and "see" what the effect is on the frequency content present. For more check the following:

http://www.cadenzarecording.com/papers

And read the first paper listed on dither. It "shows" in a visual way the effect of adding dither to a signal through FFT analysis. What you have done here is really useless, misleading, and unhelpful.

Nika

[Nika]

That's really awesome! Thanks for doing those. I'm going through my Pro Tools cert right now and went over all the different reasons you'd use dither, this helped me understand it a lot more.

Oh my. Please explain what you got from those graphs and how you are understanding this.

Thanks!
Nika

[Ryan Young]

It's a weird concept. It's when you have a fade out in your audio. Your amplitude of your wave form gets bigger and smaller depending on it's volume. With digital sound, the less volume, or sound, the lower the voltage. The digital data (bits) are binary, like all computer stuff. As you fade out, there's less and less bits jumping around, as you get to the very end, there could be a few bits just jumping up and down and you could hear it kind of (kind of a shakey on/off sound). I guess the dither adds noise to your signal to smoothen out the bits, and the signal, so you get a smoother fade out to nothing.

Likewise, when you create an in-fade and an out-fade to or from silence, you want to select the "use dither" button. And when you're crossfading 2 phase coherent (same sound, volume, recording) tracks, you want to select the "equal gain" button so you don't get a +3dB raise in your volume in the center of your fade.

Am I correct with these? It's still new to me so I might be wrong.

[Nika]

It's a weird concept. It's when you have a fade out in your audio. Your amplitude of your wave form gets bigger and smaller depending on it's volume. With digital sound, the less volume, or sound, the lower the voltage. The digital data (bits) are binary, like all computer stuff. As you fade out, there's less and less bits jumping around, as you get to the very end, there could be a few bits just jumping up and down and you could hear it kind of (kind of a shakey on/off sound). I guess the dither adds noise to your signal to smoothen out the bits, and the signal, so you get a smoother fade out to nothing.

Yes. Think of it like throwing a bunch of french fries on a cookie sheet and throwing them in the oven. They stick to the pan just a little bit as they cook. You pull it out and want to divvy them up onto four plates. If you just "dump" them they'll all go onto one plate. So you jiggle the pan back and forth gently in order to allow them to "slide" off the cookie sheet, giving you more control and a more "linear" behavior, commensurate to the angle that you're holding the pan. A little bit of random motion helps the linear behavior. It's really just dither in real life. Or try to get two jellybeans out of the jar without using your fingers in the jar.

Anyway, yes, by adding the noise to the digital signal we can disrupt the non-linear "sticky" behavior of the quantized bits and allow the resultant signal to behave more linearly. Again, check out the paper I referenced above.

Likewise, when you create an in-fade and an out-fade to or from silence, you want to select the "use dither" button.

Absolutely!

And when you're crossfading 2 phase coherent (same sound, volume, recording) tracks, you want to select the "equal gain" button so you don't get a +3dB raise in your volume in the center of your fade.

This is unrelated and there's not a simple answer.

Nika

[vieris]

Crikey! What are you intending to show? The ear doesn't hear like you are demonstrating this on the screen - we don't hear linear samples in this way. We hear sort of a windowed FFT of the waveform. In order to "look" at the effectiveness of various dither types you really need to take these various signals and run them into an FFT analyzer and "see" what the effect is on the frequency content present. For more check the following:

http://www.cadenzarecording.com/papers

And read the first paper listed on dither. It "shows" in a visual way the effect of adding dither to a signal through FFT analysis. What you have done here is really useless, misleading, and unhelpful.

Nika

i understand that you cant tell whats going on spectrally from just waveforms... these are just screenshots from my own dither test. I normalized the files so i could hear what the dither was adding (well hear better atleast).

I just thought the waveforms were interesting and thought i'd share..