KVR Audio

tommyzai · Post by **tommyzai** » Wed Feb 12, 2025 8:08 pm

I am trying to convert from 192kHz to 96kHz or possibly 48kHz, but don't want discarded higher frequencies to alias.

*Any recommendations?
*Would you recommend using a low-pass filter to remove the unwanted high stuff prior to downsampling?
*If so, at what frequency should I start removing with the filter?

BertKoor · Post by **BertKoor** » Wed Feb 12, 2025 9:12 pm

Most audio editors do a pretty good job on that, by default. Which one do you use? Have you seen actual evidence of the presence of aliasing. Or is this just another thing you saw on TikTok?

You can check for yourself. Create a sine sweep from 1kHz up to 80 kHz. Look in spectrum view: one solid line going up. Now change sample rate, and look at the spectrum again. Are there lines going down also? That's aliasing.

Also: does your material contain ultra sonics to begin with? Again: look at the spectrum.

tommyzai · Post by **tommyzai** » Wed Feb 12, 2025 11:24 pm

Tic Toc?

i am using TwistedWave and Acon Digital

mjolnir · Post by **mjolnir** » Thu Feb 13, 2025 4:12 am

Just use r8brain freeware (and/or r8brain settings within REAPER).
You don't have to worry about aliasing or losing audible high frequencies.
Those basic downsampling rates are easily covered. r8brain might the THE highest quality converter out there.

https://www.voxengo.com/product/r8brain/ <-- link here to r8brain freeware

tommyzai · Post by **tommyzai** » Thu Feb 13, 2025 2:51 pm

It seems this process is called, "Decimation." Would there be any advantage to manually using a low-pass filter to remove highs that are about the range prior to downsampling?

BertKoor · Post by **BertKoor** » Thu Feb 13, 2025 3:10 pm

tommyzai wrote: Thu Feb 13, 2025 2:51 pm Would there be any advantage to manually using a low-pass filter to remove highs that are about the range prior to downsampling?

Well:

mjolnir wrote: Thu Feb 13, 2025 4:12 am Just use r8brain freeware (and/or r8brain settings within REAPER).
You don't have to worry about aliasing or losing audible high frequencies.

^ what he said

tommyzai · Post by **tommyzai** » Thu Feb 13, 2025 3:15 pm

mjolnir wrote: Thu Feb 13, 2025 4:12 am Just use r8brain freeware (and/or r8brain settings within REAPER).
You don't have to worry about aliasing or losing audible high frequencies.
Those basic downsampling rates are easily covered. r8brain might the THE highest quality converter out there.

https://www.voxengo.com/product/r8brain/ <-- link here to r8brain freeware

In your opinion, is r8brain the best or the easiest for downsampling or both? I ask because I am discovering that all audio editors and DAWs have algorithms built in to remove the high stuff prior to downsampling. I do have and love TwistedWave. Apparently, I may already be covered as this app is using SoX in VHQ mode, which is highly regarded.

BertKoor · Post by **BertKoor** » Thu Feb 13, 2025 3:36 pm

Some posts ago I gave detailed instructions to test this stuff out with minimal and free tools.
It's easy to perform, and I urge you to just do it. Then draw your own conclusions.

tommyzai · Post by **tommyzai** » Thu Feb 13, 2025 3:39 pm

BertKoor, I can't seem to get out of the testing phase and enter into the creating phase. ;-0 I'm finally done with latency.
Tommy

BertKoor · Post by **BertKoor** » Tue Feb 25, 2025 7:56 am

You might be interested in this little demonstration:
viewtopic.php?p=9047149#p9047149

tommyzai · Post by **tommyzai** » Tue Feb 25, 2025 4:16 pm

BertKoor wrote: Tue Feb 25, 2025 7:56 am You might be interested in this little demonstration:
viewtopic.php?p=9047149#p9047149

Wow! Thanks for the demo. I realize some of the aliasing freqs are beyond our hearing, but still . . . which editor/downsampler did you find to be the cleanest? Audacity?

BertKoor · Post by **BertKoor** » Tue Feb 25, 2025 6:03 pm

Audacity does pretty well indeed, near perfect. I expect all "serious" audio editors to behave similar. R8brain is best of class, although the "free" version does cut off all above 18kHz.

The only surprise was the total absence of decimation filter in Tracktion Waveform.

mjolnir · Post by **mjolnir** » Tue Feb 25, 2025 11:34 pm

BertKoor, thanks for the correction about r8brain.

I apologize if I was misleading about r8brain cutting | not cutting high frequencies.

Many years ago there were some public comparison tests of sample conversion stuff (including downsampling, i think).
r8brain was that test's winner, so I started using then. But I never realised that the freeware version might be different than the main version. I wonder if Voxengo changed the product delivery because of the success.

Anyhow, sorry if I was misleading.
My accident, my fault.

I still say r8brain is a good choice if you don't mind the afforementioned loss above 18 kHz.
I never knew of that, but I trust BertKoor. I haven't looked at spectral waveforms for several years, but I used to sweat those kinds of details too.

But as I suffered hearing loss of my own ears above 16 kHz, I started being somewhat less fussy.
Life is funny that way.

Help Needed: Downsampling and Aliasing Prevention!