Despot - hard hitting ZDF compressor with antialiasing - development snapshots

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Is the envelope follower in a feedback compressor arrangement? Otherwise ZDF would not make any/much difference actually, except maybe if you want a better diode curve approximation, but in the feedforward compressor case it is just easier to solve it explicitly with the Lambert_W function, if for practical purposes you only use the upper branch Lambert_W0 it is pretty doable.

Cool project! Looking forward to using it once all the kinks are ironed out.

Cheers
Andrew

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It has feedforward topology. When doing this, wanted to test the concept, so picked something that's easier to solve, besides more "modern" and aggressive compression. Thought it won't make much difference, but was clearly wrong. It's subtle, but it's present. Compare with JSFX version if interested. It has different functions, but will be sufficient anyway.

If really interested, I'll add non-ZDF mode in the next snapshot.

Once I will finish this project, looking forward for more advanced tasks, like feedback compression and higher order filters. They will most likely require numerical methods and number crunching.

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dekadenz wrote: If really interested, I'll add non-ZDF mode in the next snapshot.
Would be fun, but not compulsory. Btw, did you solve this analytically? The furthest I came with envelope followers was with step invariant transform + simple waveshaping. But I've done some ZDF stuff for synth vcfs and phasers.
dekadenz wrote: Once I will finish this project, looking forward for more advanced tasks, like feedback compression and higher order filters. They will most likely require numerical methods and number crunching.
Feedback-comp seems insane, andy(cytomic) is the only one I know of who has done it that way, but there surely must be some others.

Cheers
Andrew

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If the knee seems too hard, remember you can mix it with the dry signal in your DAW (most likely). Zero latency!

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I just want to confirm that 32bit version is working fine.
It's easy if you know how

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New build was released.

Now with adjustable attack and release and any sample rates support. Make sure you're tried low-aliasing zero attack.
Ichad.c wrote: Would be fun, but not compulsory. Btw, did you solve this analytically? The furthest I came with envelope followers was with step invariant transform + simple waveshaping. But I've done some ZDF stuff for synth vcfs and phasers.
Indeed. True TPT/ZDF and no trickery. I think I'll make separate non-ZDF version in order to avoid adding extra option and confusing users. Developed ZDF envelope follower not for disabling it.

By the way, solving the general case for arbitrary attack and release was really hardcore. One typo got into huge equations and it took long to figure out what was wrong. Finally fixed, enjoy.

Future version will have less limited attack/release and nonlinear sliders for easy dialing. Without nonliear I could not make the scale too wide without making it inсonvinient.

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I think ZDF should become stable in any plug-in where it's possible :oops:
circuit modeling and 0-dfb filters are cool

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Regarding aliasing: did a sine test on zero attack and 100 ms release on 176.4 kHz.

Image

Not pristine like older non-ZDF version (because of the simplified functions), but I think it's acceptable for early dev version. Many hyped and expensive plugins has much, much worse aliasing in fact, even with oversampling.
penguinfromdeep wrote:I think ZDF should become stable in any plug-in where it's possible :oops:
Considering the complexity of development and completely dampened market, it's impossible. Only DSP aficionados doing someting new without money involved.
With current situation, it's far more viable to develop GUI for peanuts, strap some 60's digital filters and sell for 20$.
A plugin with ZDF should cost 100$ minimum, not 20.

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Hey dekadenz, thanks for providing this to the community! Looking forward to giving it a spin.
A well-behaved signature.

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nah ZDF is still $200 material.

they should also be standardised every place you don't understand them, but are certainly willing to pay for them.
you come and go, you come and go. amitabha neither a follower nor a leader be tagore "where roads are made i lose my way" where there is certainty, consideration is absent.

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Before I'll release the next build with nonlinear attack-release scale and two knees - soft and hard, I want some advice from potential users.

Is such a table is ok?

Code: Select all

   0     -     0.01  ms  -    0.001 ms step
   0.01  -     0.1   ms  -    0.01
   0.1   -     1     ms  -    0.05
   1     -    10     ms  -    0.5
  10     -   100     ms  -    5
 100     -  1000     ms  -   10
1000     -  3000     ms  -  100
3000     -  6000     ms  -  500

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Have You updated?

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No, waiting for for some replies. Not sure if this attack-release scale is ideal and covers everything. Any ideas?

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So, no suggestions. Fine, left it to my tastes.

Now, almost everything is in place, only oversampling is left for the future build. It will be HQ linear phase oversampling with user selectable ratios from 2x and up, no quality/latency compromises, which means the latency will be pretty high with oversampling enabled (0 without). Not an issue for latency-compensated hosts, but not suitable for real-time live use with oversampling.

On the bright side, linear phase and latency compensation means it can be used for parallel compression and won't cause any phase issues.

A new build is out.

1432326119
- stepped nonlinear attack/release scale
- hard and soft knee

Notes: quieter signal in soft knee mode is not a bug. This is 100% soft knee, it begins compressing very early (even from zero signal), so the drive should be backed off if you want less compression.

http://stash.reaper.fm/v/24139/despot-1432326119.zip

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Compressors can get technical, maybe try posting the question in the DSP subforum.
I wouldn't worry so much about aliasing, most material with a broad frequency spectrum will mask most if not all of the sound of aliasing, if it's at a low enough level. You should also consider CPU load, having large delays is sure to slow things down.

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