Airwindows

Biquad

TL;DW: Biquad is the Airwindows implementation of a biquad filter.

This little puppy is really flexible!

That’s true of any biquad filter, but I find most of them are really flexible and slightly plastic. Traditionally biquads require special handling, because you can’t push them too far before they break, and also they sound ‘DAW-y’ and synthetic. Not in the same way as linear-phase EQs, mind you, but still with something about them that feels digital.

So I fixed that :) with a couple caveats. Firstly, part of it is brute force. I figured that if biquads run into trouble with 32-bit coefficients on some filter curves, and it’s widely known that you should do things like run ’em in series to get better behavior, we could always run long doubles and be totally sure they work as intended. Overkill? Meh. Sure, but it’s known that these break due to losing control of themselves due to not long enough wordlengths. Why wouldn’t they work and sound better with long enough wordlengths? And so they do. Also, you get to run simpler biquads if you don’t have to run lots of them, so it averages out. I think it’s just a matter of audio DSP coders stubbornly insisting on not using long data words on the grounds it doesn’t matter to the sound. This, when the filters go obviously wrong under some conditions for just that reason? Anyway, here’s long double biquad, because nobody else was doing it far as I know.

The second part is trickier, because if you use it you remove some functionality. Biquads make great DC blockers. But, biquads also work through the summing of many delay taps, all very close together. Some are on input, others on output. They’re a mixing of multiple copies of the signal.

That means Console applies to the biquad filter.

We already knew that, of course: I’ve long observed that you can put Console (or BussColors4/ConsoleBuss4) around a bog-standard DAW EQ and get an enhanced sound out of it. Mind you, I wasn’t controlling that EQ, but it still worked. But now, I have Console5 (not 6, but I COULD do 6 in the right context) built right into Biquad. So, it does expect to have a signal between -1 and 1 (or lower than 0dBFS in the DAW), and that means Biquad itself can’t remove huge DC offsets ten times the size of the audio content. (It can still remove smaller offsets just fine). And it runs into basically PurestConsoleChannel, does the biquad, then uses PurestConsoleBuss and goes out to an inverse/dry/wet control (which itself has multiple uses).

What’s a biquad, you ask? The Airwindows biquad uses four of the six common biquad options (I prefer to do shelves with subtractive/additive use of filtered audio). The top control has settings one through four. They go lowpass, highpass, bandpass and notch. That’s what I consider the platonic set of biquads, and it lets the filter design be simple and clear. You can set a frequency (in ‘amount of the audio range’) from ‘zero’ to ‘one’. There’ll be EQs with more specific frequencies, that’s easy, but this is proof of concept and to be used by ear, plus it will always cover DC to Nyquist at any sample rate. Zero is not really DC, because that kills the biquad: also, One is not really the Nyquist frequency (half the sample rate) for the same reason. But, they act a lot like they range that far, because the high resolution lets Biquad calculate things accurately even that far out of the normal range.

They don’t update/recalculate every sample, but the way I’ve defined the data structures means they could if you wanted them to (at a cost in higher CPU-eating). The code’s MIT licensed open source, so GPL people can just take it if they credit me, and all the projects that are using the Airwindows library are advised to get up to date and include this one. Set right, it is THE ultimate sample-instrument tone shaper to sit ‘under the hood’ and voice somebody’s musical product after the sample-playback stuff is taken care of. You’ll be seeing a lot of stuff come out that uses this code, as there are many plugins that require this type of filter to work, often ones that will benefit from the sonic improvements that are part of Biquad.

More will be revealed. Suffice to say this is a very useful building block that’ll allow for some very special plugins.

I did it because thanks to Patreon I’m still here working full-time years after I went open source. It’s really that simple: I didn’t have to stop. Nor did I have to get a ‘real job’, or make all my work proprietary or any of that. It’s not a huge living, but in fairness if I start earning a huge living I’ll only buy gear to make stuff that I can sell to people at cost, so I’m not destined for Cancun or Vegas in any event. I like what I do, so more money only means I get to do more of it. Maybe I can buy rarer gear and then make plugins of it, or a computer that could really start to make proper use of modern DAW-like things like VCV Rack (which I can’t really run that well on my older iMac… not at the scale I’d find necessary).

Also, like I said in the video, DISlike and subscribe on YouTube. I want to do an experiment to see if that hurts or actually helps. Since I can get away with it and normal youtubers can’t, please DISlike and subscribe to my videos, and I’ll see if that is really just another ‘engagement’ metric or hurts or maybe even is the secret to why so much junk thrives on youtube (maybe it’s better than likes! We’ll find out)

Date July 7, 2019
Author Chris
Comments 3 Comments

DeHiss

TL;DW: DeHiss tries to suppress background hiss, like a hiss gate.

DeHiss.zip(350k)

Here’s a request: I was asked to put DeHiss out, so while I’m working on newer stuff you can have an up-to-date and VST-ified DeHiss plugin.

This acts like a filtery gate. It tries to apply a lowpass filter to suppress quiet background noise whenever loud bright treble isn’t happening. You can use it in creative ways, but it really was designed to suppress hiss from a cheap USB condenser mic. Sort of an experiment. It’s got a dry/wet now in case that comes in handy. I’m not sure how much else is out there specifically like this, but then I’m not sure how much call there is for it in the first place :)

But thanks to Patreon I’m free to do stuff that is only useful to one person. And there was one person who actually asked for this to come out as VST, so it’s not even an imaginary person! There’ll be other things that come out which are very noncommercial, simply because I can: I don’t have to stick to what will sell. (I do still have some killer ‘take my money!’ grade stuff also coming, that’s new: same deal, if you can then please act like you’d buy perpetual DRM-free license for $50, good for all your computers at once, and add that much yearly to my Patreon. If you can. Whatever you’re comfortable with)

I hope you like DeHiss. But it’s okay if you don’t, because I know there’s a person who specifically needed it, and that’s good enough for me :)

Date June 30, 2019
Author Chris
Comments 8 Comments

DeRez2

TL;DW: DeRez2 brings more authentic retro-digital hardware tones.

DeRez2.zip(359k)

Surprise bitcrusher update! :D

Sometimes when I bump version numbers it’s because I’ve come up with a way to transform a plugin. Sometimes it’s because I can leave the existing sound the same but add new functionality. This time it’s both.

DeRez is the Airwindows bitcrusher that interpolates a sample between sample-rate-crushed outputs so the top end is smooth rather than gritty, and the only (far as I know) ANALOG bitcrusher (or at least floating point resolution?). That means you can set it to 32 and a third K sample rate, and seven point one three five bits. By ear, please: if you are needing to set a third of a K of sample rate without hearing it, I can’t help you. The point being, DeRez was already cool as a continuous-rate rate-crusher and arbitrary bit depth linear bitcrusher. I don’t think anyone else has that (of course now they can: it’s open source MIT license, so just credit Airwindows and code away)

How do you make that not just better but way better?

DeRez2’s ‘Hard’ control maxes out as the previous plugin (with a few behind-the-scenes upgrades, but exactly the same algorithm at the heart). But the interesting part is when you turn it OFF: set ‘Hard’ to zero. Two things happen.

The sample-rate crusher begins to incorporate intermediate samples in a different way. When it’s changing, it saves up the previous sample… and uses that, not an interpolation, as the intermediate value. It’s trying to bridge the gap between rate-crushed values with a dry sample value. This causes a strange grungy transparency and a zone between ‘clean’ and rate-crushed that’s eerily reminiscent of old digital hardware. It stops sounding in-the-box, even though it remains completely bitcrushed with a totally different texture.

The bit-crusher remains ‘analog’ (arbitrary bit depth, like 12 and a half bits) but on full soft, it uses uLaw encode and decode, so it becomes nonlinear! Same as the famous Aphex Twin ‘long play DAT’ and old retro nonlinear digital hardware, the loud parts get bigger ‘steps’ and quiet stuff gets smaller ‘steps’, producing a totally different tonality. You can use this and the sample-rate crush at the same time, subtly or obviously, to dial in vintage-digital tonalities that are totally satisfying and convincing, but completely different from the source audio. You’d never know it started out different because it winds up sounding completely right.

I’ve been asked for dedicated emulations of vintage sampler gear. Instead, try this: no copying, but a new way to get that kind of tonality and dial it in to taste. If you need the darkening and texture of classic samplers, DeRez2 will do the same job in a new way with features the real retro gear didn’t have.

Why does this one have the dry/wet? Because since the rate-crusher uses the previous sample for transitions, blending it with dry makes the transitions further softened with averaging. You can fade between pristine and clear, dark and cloudy, and totally retro-sampler thanks to that effect (which wouldn’t have happened with the previous DeRez, though you can try it on full Hard and see)

What’s with the halfway settings between Soft and Hard? It engages wet/dry balance on the uLaws inside the plugin. If you do that to uLaw, you get weird broken results and it doesn’t work nicely. It just so happens that going from soft to halfway gives a big volume and grunge boost. So rather than have it as a clean off/on control, the Hard control lets you use that unforeseen weirdness as an intentional effect. If you have it dialed in but you’d like to punch up the aggression for effect, automate the Hard control and use it as a booster, for a unique result.

I forgot to specify in the video (since I was having far too much fun dialing in tones) but to keep me doing this type of work, join my Patreon. This week, keeping me on the job worked out really well for everyone! :)

Date June 23, 2019
Author Chris
Comments 10 Comments

Podcast

TL;DW: Podcast is a simpler pile of curve-style compressors with hard clipping.

Podcast.zip(354k)

Here’s the followup to PodcastDeluxe, as promised. Podcast is the same technique, multiple compressors that are the precursor to curve and Recurve, but simplified: without the phase rotators, without the full-on attempt to do ‘radio broadcast’ style tricks.

This also means Podcast can have a dry/wet control, because there aren’t any phase rotations delaying things. In fact, Podcast runs no latency and can work very well as a ‘glue’ style buss compressor… so long as you don’t want ‘pumping and swelling’ effects, or sidechainy whooshes of level. That’s because Podcast is still in the curve school of compressors and quits changing levels if the input goes silent.

It also hard-clips the output, making it a kind of ‘safety compressor’: though it’s not clean like a limiter, it’ll strike a balance between dynamics processor and distortion device. You can use it on drums and things meant to be aggressively smashed, or turn it way down and use it as a clean buss comp.

Treat this as another flavor of compressor from Airwindows, and see if it finds uses for you. The greater simplicity of Podcast (much like PodcastDeluxe, heavily updated from the original versions) makes it more adaptable to different purposes, while it remains simple and un-fiddly, delivering its effects with whatever intensity and blend you like. :)

If you like it, ask yourself if you’d have paid $50 for this (or any other recent plugin of mine) if I was selling them in the normal manner. If so, you should feel good about zipping over to Patreon and joining for $50 a year (or upping your amount if you’re really enthusiastic). People doing this have let me do things like buy 1000 tiny LEDs for 2 cents each, and if I can do that then I can work out ways to bring things like hardware kits to you, just as generously. And that sounds like fun!

Date June 16, 2019
Author Chris
Comments 4 Comments

Chris

Biquad

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DeRez2

Podcast

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