feat: add tiltfilter example
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@prefix lv2: <http://lv2plug.in/ns/lv2core#> .
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@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
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<urn:nymph:examples:multimode-filter>
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<urn:nymph:examples:multimodefilter>
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a lv2:Plugin ;
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lv2:binary <libmultimodefilter.so> ;
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rdfs:seeAlso <multimodefilter.ttl> .
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@prefix lv2: <http://lv2plug.in/ns/lv2core#> .
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@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
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<urn:nymph:examples:tiltfilter>
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a lv2:Plugin ;
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lv2:binary <libtiltfilter.so> ;
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rdfs:seeAlso <tiltfilter.ttl> .
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@prefix bufs: <http://lv2plug.in/ns/ext/buf-size#> .
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@prefix doap: <http://usefulinc.com/ns/doap#> .
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@prefix foaf: <http://xmlns.com/foaf/0.1/> .
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@prefix lv2: <http://lv2plug.in/ns/lv2core#> .
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@prefix opts: <http://lv2plug.in/ns/ext/options#> .
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@prefix params: <http://lv2plug.in/ns/ext/parameters#> .
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@prefix props: <http://lv2plug.in/ns/ext/port-props#> .
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@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
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@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
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@prefix units: <http://lv2plug.in/ns/extensions/units#> .
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<urn:nymph:examples:tiltfilter>
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a lv2:Plugin , lv2:FilterPlugin , doap:Project ;
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lv2:optionalFeature lv2:hardRTCapable , bufs:boundedBlockLength , opts:options ;
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opts:supportedOption bufs:nominalBlockLength ,
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bufs:maxBlockLength ,
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params:sampleRate ;
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lv2:port [
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a lv2:InputPort, lv2:AudioPort ;
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lv2:index 0 ;
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lv2:name "Audio In" ;
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lv2:symbol "in" ;
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],
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[
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a lv2:OutputPort, lv2:AudioPort ;
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lv2:index 1 ;
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lv2:name "Audio Out" ;
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lv2:symbol "out" ;
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],
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[
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a lv2:InputPort, lv2:ControlPort ;
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lv2:index 2 ;
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lv2:name "Cutoff" ;
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lv2:symbol "cutoff" ;
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lv2:default 10000.0 ;
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lv2:minimum 20.0 ;
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lv2:maximum 20000.0 ;
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units:unit units:hz ;
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],
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[
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a lv2:InputPort, lv2:ControlPort ;
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lv2:index 3 ;
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lv2:name "Steepness" ;
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lv2:symbol "steepness" ;
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lv2:default 1.0 ;
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lv2:minimum 0.0 ;
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lv2:maximum 1.0 ;
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],
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[
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a lv2:InputPort, lv2:ControlPort ;
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lv2:index 4 ;
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lv2:name "Filter mode" ;
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lv2:symbol "mode" ;
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lv2:default 0 ;
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lv2:minimum 0 ;
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lv2:maximum 2 ;
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lv2:portProperty lv2:enumeration, lv2:integer ;
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lv2:scalePoint [
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rdfs:label "Lowpass" ;
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rdf:value 0 ;
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],
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[
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rdfs:label "Highpass" ;
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rdf:value 1 ;
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],
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[
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rdfs:label "Bandpass" ;
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rdf:value 2;
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] ;
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];
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rdfs:comment """
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A tilt EQ audio filter.
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""" ;
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doap:name "nymph tilt filter" ;
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doap:license <https://spdx.org/licenses/MIT> ;
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doap:maintainer [
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foaf:name "Christopher Arndt" ;
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foaf:mbox <mailto:info@chrisarndt.de> ;
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foaf:homepage <https://gitlab.com/SpotlightKid/nymph> ;
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] ;
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lv2:microVersion 0 ;
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lv2:minorVersion 1 .
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@ -0,0 +1,165 @@
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##
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## Tilt Filter
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##
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## Nim translation of this Rust implementation:
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##
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## https://github.com/ardura/Actuate/blob/main/src/fx/ArduraFilter.rs
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##
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## Inspired by https://www.musicdsp.org/en/latest/Filters/267-simple-tilt-equalizer.html
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## Lowpass, Bandpass, Highpass based off tilt filter code
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import math
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const
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slopeNeg = -60.0
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amp = 6.0 / ln(2.0)
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denorm = pow(10.0, -30.0)
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minFreq = 20.0
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maxFreq = 20_000.0
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type
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FilterMode* = enum
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fmLowPass, fmBandPass, fmHighPass
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TiltFilter* = object
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# Filter parameters
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sampleRate: float64
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centerFreq: float
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steepness: float
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mode: FilterMode
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# Filter tracking / internal
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needsUpdate: bool
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sampleRateX3: float64
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lowGain: float
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highGain: float
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a: float
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b: float
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lpOut: float
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# Band pass separate vars
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bandALow: float
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bandBLow: float
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bandOutLow: float
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bandAHigh: float
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bandBHigh: float
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bandOutHigh: float
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# Super useful function to scale an sample 0-1 into other ranges
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proc scaleRange(sample, minOutput, maxOutput: float): float =
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result = clamp(sample * (maxOutput - minOutput) + minOutput, minOutput, maxOutput)
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proc initTiltFilter*(centerFreq, steepness: float, mode: FilterMode = fmLowPass, sampleRate: float64 = 48_000.0): TiltFilter =
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let sampleRateX3 = 3.0 * sampleRate
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case mode:
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# These are the gains for the slopes when math happens later
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of fmLowPass:
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result.lowGain = exp(0.0 / amp) - 1.0
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result.highGain = exp(slopeNeg / amp) - 1.0
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of fmBandPass:
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result.lowGain = exp(0.0 / amp) - 1.0
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result.highGain = exp(slopeNeg / amp) - 1.0
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of fmHighPass:
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result.lowGain = exp(slopeNeg / amp) - 1.0
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result.highGain = exp(0.0 / amp) - 1.0
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let omega = 2.0 * PI * centerFreq
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let n = 1.0 / (scaleRange(steepness, 0.98, 1.2) * (sampleRateX3 + omega))
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result.a = 2.0 * omega * n
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result.bandALow = result.a
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result.bandAHigh = result.a
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result.b = (sampleRateX3 - omega) * n
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result.bandBLow = result.b
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result.bandBHigh = result.b
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result.lpOut = 0.0
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result.bandOutLow = 0.0
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result.bandOutHigh = 0.0
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result.centerFreq = centerFreq
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result.sampleRateX3 = sampleRateX3
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result.steepness = steepness
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result.sampleRate = sampleRate
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result.mode = mode
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result.needsUpdate = true
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proc setMode*(self: var TiltFilter, mode: FilterMode) =
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if mode != self.mode:
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self.mode = mode
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self.needsUpdate = true
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proc setCenterFreq*(self: var TiltFilter, value: float) =
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let freq = value.clamp(minFreq, maxFreq)
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if freq != self.centerFreq:
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self.centerFreq = freq
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self.needsUpdate = true
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proc setSteepness*(self: var TiltFilter, value: float) =
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let steepness = value.clamp(0.0, 1.0)
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if steepness != self.steepness:
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self.steepness = steepness
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self.needsUpdate = true
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proc setSampleRate*(self: var TiltFilter, sampleRate: float) =
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if sampleRate != self.sampleRate:
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self.sampleRate = sampleRate
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self.sampleRateX3 = self.sampleRate * 3.0
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self.needsUpdate = true
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proc reset*(self: var TiltFilter) =
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discard
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proc update*(self: var TiltFilter) =
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if self.needsUpdate:
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case self.mode:
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of fmLowPass:
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let omega = 2.0 * PI * self.centerFreq
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let n = 1.0 / (scaleRange(self.steepness, 0.98, 1.2) * (self.sample_rate_x3 + omega))
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self.b = (self.sampleRateX3 - omega) * n
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self.lowGain = exp(0.0 / amp) - 1.0
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self.highGain = exp(slopeNeg / amp) - 1.0
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of fmBandPass:
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let width = self.steepness * self.steepness * 500.0
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let lowOmega = 2.0 * PI * (self.centerFreq - width).clamp(20.0, 16_000.0)
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let lowN = 1.0 / (scaleRange(self.steepness, 0.98, 1.2) * (self.sampleRateX3 + lowOmega))
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self.bandALow = 2.0 * lowOmega * lowN
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self.bandBLow = (self.sampleRateX3 - lowOmega) * lowN
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let highOmega = 2.0 * PI * (self.centerFreq + width).clamp(20.0, 16_000.0);
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let highN = 1.0 / (scaleRange(self.steepness, 0.98, 1.2) * (self.sampleRateX3 + highOmega))
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self.bandAHigh = 2.0 * highOmega * highN
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self.bandBHigh = (self.sampleRateX3 - highOmega) * highN
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self.lowGain = exp(0.0 / amp) - 1.0
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self.highGain = exp(slopeNeg / amp) - 1.0
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of fmHighPass:
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let omega = 2.0 * PI * self.centerFreq
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let n = 1.0 / (scaleRange(self.steepness, 0.98, 1.2) * (self.sampleRateX3 + omega))
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self.a = 2.0 * omega * n
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self.b = (self.sampleRateX3 - omega) * n
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self.lowGain = exp(slopeNeg / amp) - 1.0
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self.highGain = exp(0.0 / amp) - 1.0
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self.needsUpdate = false
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##
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## Process the input sample using the tilt filter
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##
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proc process*(self: var TiltFilter, sample: float): float =
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if self.mode == fmBandPass:
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self.bandOutLow = self.bandALow * sample + self.bandBLow * self.bandOutLow
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let temp = sample + self.highGain * self.bandOutLow + self.lowGain * (sample - self.bandOutLow)
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self.bandOutHigh = self.bandAHigh * temp + self.bandBHigh * self.bandOutHigh
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result = temp + self.lowGain * self.bandOutHigh + self.highGain * (temp - self.bandOutHigh) + denorm
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else:
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self.lpOut = self.a * sample + self.b * self.lpOut;
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result = sample + self.lowGain * self.lpOut + self.highGain * (sample - self.lpOut) + denorm
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## A tilt EQ / filter LV2 plugin
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import nymph
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import paramsmooth
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import tiltfilter
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const
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PluginUri = "urn:nymph:examples:tiltfilter"
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minFreq = 20.0
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maxFreq = 20_000.0
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type
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SampleBuffer = UncheckedArray[cfloat]
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PluginPort {.pure.} = enum
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Input, Output, Frequency, Steepness, Mode
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TiltFilterPlugin = object
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input: ptr SampleBuffer
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output: ptr SampleBuffer
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freq: ptr cfloat
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steepness: ptr cfloat
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mode: ptr cfloat
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flt: TiltFilter
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smoothFreq: ParamSmooth
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proc instantiate(descriptor: ptr Lv2Descriptor; sampleRate: cdouble;
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bundlePath: cstring; features: ptr UncheckedArray[ptr Lv2Feature]):
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Lv2Handle {.cdecl.} =
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try:
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let plug = createShared(TiltFilterPlugin)
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plug.flt = initTiltFilter(10_000.0, 1.0, fmLowPass, sampleRate)
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plug.smoothFreq = initParamSmooth(20.0, sampleRate)
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return cast[Lv2Handle](plug)
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except OutOfMemDefect:
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return nil
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proc connectPort(instance: Lv2Handle; port: cuint;
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dataLocation: pointer) {.cdecl.} =
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let plug = cast[ptr TiltFilterPlugin](instance)
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case cast[PluginPort](port)
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of PluginPort.Input:
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plug.input = cast[ptr SampleBuffer](dataLocation)
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of PluginPort.Output:
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plug.output = cast[ptr SampleBuffer](dataLocation)
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of PluginPort.Frequency:
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plug.freq = cast[ptr cfloat](dataLocation)
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of PluginPort.Steepness:
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plug.steepness = cast[ptr cfloat](dataLocation)
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of PluginPort.Mode:
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plug.mode = cast[ptr cfloat](dataLocation)
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proc activate(instance: Lv2Handle) {.cdecl.} =
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let plug = cast[ptr TiltFilterPlugin](instance)
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plug.flt.reset()
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proc run(instance: Lv2Handle; nSamples: cuint) {.cdecl.} =
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let plug = cast[ptr TiltFilterPlugin](instance)
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let freq = plug.freq[].clamp(minFreq, maxFreq)
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plug.flt.setMode(plug.mode[].clamp(0.0, 2.0).FilterMode)
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plug.flt.setSteepness(plug.steepness[])
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for pos in 0 ..< nSamples:
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plug.flt.setCenterFreq(plug.smoothFreq.process(freq))
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plug.flt.update()
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plug.output[pos] = plug.flt.process(plug.input[pos])
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proc deactivate(instance: Lv2Handle) {.cdecl.} =
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discard
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proc cleanup(instance: Lv2Handle) {.cdecl.} =
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freeShared(cast[ptr TiltFilterPlugin](instance))
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proc extensionData(uri: cstring): pointer {.cdecl.} =
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return nil
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proc NimMain() {.cdecl, importc.}
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proc lv2Descriptor(index: cuint): ptr Lv2Descriptor {.
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cdecl, exportc, dynlib, extern: "lv2_descriptor".} =
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NimMain()
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if index == 0:
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result = createShared(Lv2Descriptor)
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result.uri = cstring(PluginUri)
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result.instantiate = instantiate
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result.connectPort = connectPort
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result.activate = activate
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result.run = run
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result.deactivate = deactivate
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result.cleanup = cleanup
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result.extensionData = extensionData
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@ -26,7 +26,8 @@ type Example = tuple
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const examples = to_table({
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"amp": "urn:nymph:examples:amp",
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"miditranspose": "urn:nymph:examples:miditranspose",
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"multimodefilter": "urn:nymph:examples:multimode-filter",
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"multimodefilter": "urn:nymph:examples:multimodefilter",
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"tiltfilter": "urn:nymph:examples:tiltfilter",
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})
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