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Old 04-26-2013, 06:26 AM   #1
mawi
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Default Anti Aliasing in ReaComp do not work (FIXED)

Hello, I have testet the Anti Aliasing funktion in ReaComp and found out that this do not work. See my test

REAPER v4.33/x64, Win7 Pro SP1/x64
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Old 04-26-2013, 02:17 PM   #2
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Here a Video Demonstration how I think Anti-Aliasing should work (from 2:02 min)
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Old 04-26-2013, 09:52 PM   #3
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Can you make a video of the same test with ReaComp and AA turned off? The aliasing, while obviously present in the video, does seem to be at least 70-80dB below the peak, which isn't bad (the AA Filter ReaComp uses isn't the steepest, it is trying not to be too harsh on phase).
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Old 04-27-2013, 07:34 AM   #4
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Hello Justin, thank you for your reply. Here are some more videos where I testet Anti-Aliasing with JS: Synthesis/sine_sweep. Also ReaComp and AA turned off. I know the peaks are very low but it seems it makes no difference between AA "None" and "64x". That's why I was taken aback. Incidentally, Cytomic The Glue does a very good job, I think.

Aliasing Test ReaComp Anti Aliasing None.avi

Aliasing Test ReaComp Anti Aliasing x64.avi

Aliasing Test The Glue Oversampling Off.avi

Aliasing Test The Glue Oversampling x16.avi

So, did I testet Anti-Aliasing wrong or why I can not see a difference between AA "None" and "64x" in ReaComp?
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Old 04-27-2013, 08:09 AM   #5
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Looking into this now, it does seem to not be working, actually. The 2x AA mode actually does seem to have a slight advantage here, but the higher modes do not.
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Old 04-27-2013, 08:25 AM   #6
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Quote:
Originally Posted by Justin View Post
Looking into this now, it does seem to not be working, actually. The 2x AA mode actually does seem to have a slight advantage here, but the higher modes do not.
Thanks to look into this.
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Old 04-27-2013, 09:30 AM   #7
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Here's an updated win32 build of reacomp with fixed filters (it only ends up being about 3-6dB of reduction for aliasing, but maybe that'll be meaningful -- otherwise we could look at other filter types too).
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Old 04-27-2013, 10:17 AM   #8
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Where can I find an updated reacomp? Is there also a 64 bit version? I'm no expert, and for a clean sound I would suggest better anti aliasing filter.
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Old 04-28-2013, 03:57 PM   #9
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Sorry, meant to include a link. Here's the win32 build (sorry, no 64 bit version at the moment). Please give your comments in this thread.

http://landoleet.org/reacomp-win32-aafix.zip
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Old 04-28-2013, 04:16 PM   #10
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Quote:
Originally Posted by Justin View Post
it only ends up being about 3-6dB of reduction for aliasing
Surely not for x64? That wouldn't seem worth it
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Old 04-28-2013, 04:55 PM   #11
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Thanks for the efforts! I only see a small improvement. I have no idea how that works with the anti-aliasing. Maybe I should just live with it.
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Old 02-26-2017, 04:40 AM   #12
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i can confirm that "AA" on ReaComp does basically nothing in regards to aliasing.
this is a comparison of ReaComp with/without "AA" (64x)
https://i.imgur.com/AIQ8hge.png

and this is ReaComp with the project sample rate set to 2,822,400 Hz (64 x 44,100 Hz)
https://i.imgur.com/yWpkk3m.png

i would hardly call this issue "FIXED"

Last edited by bezusheist; 02-26-2017 at 06:15 AM.
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Old 02-26-2017, 07:10 AM   #13
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Thankfully there are hundreds of other compressors on the market which have better AA.
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Old 02-26-2017, 07:21 AM   #14
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well i myself do not use oversampling on any plug-ins, but i figured maybe others do.
it's a little mis-leading to have the option there if it doesn't really do anything.
i would just remove the option.
it just causes confusion and complaints.
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Old 03-01-2017, 03:28 PM   #15
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filter choice/design is a crucial part to the re-sampling process.
having said that...

ReaComp "AA" filters: green = 2x, red = 64x



Reaper 5.33 Extreme HQ 2x OS filter



again, i don't need this fixed for me because i don't use the AA.
but others who do use it may want it fixed and should at least know that it doesn't really work.
Attached Images
File Type: png reacomp_aa_2x_64x.png (18.1 KB, 884 views)
File Type: png reaper_xtrm_os.png (18.6 KB, 719 views)

Last edited by bezusheist; 03-01-2017 at 03:59 PM.
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