feat: add tiltfilter example

examples/amp.lv2/amp.ttl

@@ -1,7 +1,7 @@
 @prefix bufs: <http://lv2plug.in/ns/ext/buf-size#> .
 @prefix doap: <http://usefulinc.com/ns/doap#> .
 @prefix foaf: <http://xmlns.com/foaf/0.1/> .
-@prefix lv2:  <http://lv2plug.in/ns/lv2core#> .
+@prefix lv2: <http://lv2plug.in/ns/lv2core#> .
 @prefix opts: <http://lv2plug.in/ns/ext/options#> .
 @prefix params: <http://lv2plug.in/ns/ext/parameters#> .
 @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .

examples/amp.lv2/manifest.ttl

@@ -1,4 +1,4 @@
-@prefix lv2:  <http://lv2plug.in/ns/lv2core#> .
+@prefix lv2: <http://lv2plug.in/ns/lv2core#> .
 @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
 
 <urn:nymph:examples:amp>

examples/miditranspose.lv2/manifest.ttl

@@ -1,4 +1,4 @@
-@prefix lv2:  <http://lv2plug.in/ns/lv2core#> .
+@prefix lv2: <http://lv2plug.in/ns/lv2core#> .
 @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
 
 <urn:nymph:examples:miditranspose>

examples/multimodefilter.lv2/manifest.ttl

@@ -1,7 +1,7 @@
-@prefix lv2:  <http://lv2plug.in/ns/lv2core#> .
+@prefix lv2: <http://lv2plug.in/ns/lv2core#> .
 @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
 
-<urn:nymph:examples:multimode-filter>
+<urn:nymph:examples:multimodefilter>
     a lv2:Plugin ;
     lv2:binary <libmultimodefilter.so> ;
     rdfs:seeAlso <multimodefilter.ttl> .

examples/multimodefilter.lv2/multimodefilter.ttl

@@ -1,11 +1,11 @@
 @prefix bufs: <http://lv2plug.in/ns/ext/buf-size#> .
 @prefix doap: <http://usefulinc.com/ns/doap#> .
 @prefix foaf: <http://xmlns.com/foaf/0.1/> .
-@prefix lv2:  <http://lv2plug.in/ns/lv2core#> .
+@prefix lv2: <http://lv2plug.in/ns/lv2core#> .
 @prefix opts: <http://lv2plug.in/ns/ext/options#> .
 @prefix params: <http://lv2plug.in/ns/ext/parameters#> .
 @prefix props: <http://lv2plug.in/ns/ext/port-props#> .
-@prefix rdf:   <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
+@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
 @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
 @prefix units: <http://lv2plug.in/ns/extensions/units#> .
 

examples/tiltfilter.lv2/manifest.ttl

@@ -0,0 +1,8 @@
+@prefix lv2: <http://lv2plug.in/ns/lv2core#> .
+@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
+
+<urn:nymph:examples:tiltfilter>
+    a lv2:Plugin ;
+    lv2:binary <libtiltfilter.so> ;
+    rdfs:seeAlso <tiltfilter.ttl> .
+

examples/tiltfilter.lv2/tiltfilter.ttl

@@ -0,0 +1,90 @@
+@prefix bufs: <http://lv2plug.in/ns/ext/buf-size#> .
+@prefix doap: <http://usefulinc.com/ns/doap#> .
+@prefix foaf: <http://xmlns.com/foaf/0.1/> .
+@prefix lv2: <http://lv2plug.in/ns/lv2core#> .
+@prefix opts: <http://lv2plug.in/ns/ext/options#> .
+@prefix params: <http://lv2plug.in/ns/ext/parameters#> .
+@prefix props: <http://lv2plug.in/ns/ext/port-props#> .
+@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
+@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
+@prefix units: <http://lv2plug.in/ns/extensions/units#> .
+
+<urn:nymph:examples:tiltfilter>
+    a lv2:Plugin , lv2:FilterPlugin , doap:Project ;
+
+    lv2:optionalFeature lv2:hardRTCapable , bufs:boundedBlockLength , opts:options ;
+
+    opts:supportedOption bufs:nominalBlockLength ,
+                         bufs:maxBlockLength ,
+                         params:sampleRate ;
+
+    lv2:port [
+        a lv2:InputPort, lv2:AudioPort ;
+        lv2:index 0 ;
+        lv2:name "Audio In" ;
+        lv2:symbol "in" ;
+    ],
+    [
+        a lv2:OutputPort, lv2:AudioPort ;
+        lv2:index 1 ;
+        lv2:name "Audio Out" ;
+        lv2:symbol "out" ;
+    ],
+    [
+        a lv2:InputPort, lv2:ControlPort ;
+        lv2:index 2 ;
+        lv2:name "Cutoff" ;
+        lv2:symbol "cutoff" ;
+        lv2:default 10000.0 ;
+        lv2:minimum 20.0 ;
+        lv2:maximum 20000.0 ;
+        units:unit units:hz ;
+    ],
+    [
+        a lv2:InputPort, lv2:ControlPort ;
+        lv2:index 3 ;
+        lv2:name "Steepness" ;
+        lv2:symbol "steepness" ;
+        lv2:default 1.0 ;
+        lv2:minimum 0.0 ;
+        lv2:maximum 1.0 ;
+    ],
+    [
+        a lv2:InputPort, lv2:ControlPort ;
+        lv2:index 4 ;
+        lv2:name "Filter mode" ;
+        lv2:symbol "mode" ;
+        lv2:default 0 ;
+        lv2:minimum 0 ;
+        lv2:maximum 2 ;
+        lv2:portProperty lv2:enumeration, lv2:integer ;
+        lv2:scalePoint [
+            rdfs:label "Lowpass" ;
+            rdf:value 0 ;
+        ],
+        [
+            rdfs:label "Highpass" ;
+            rdf:value 1 ;
+        ],
+        [
+            rdfs:label "Bandpass" ;
+            rdf:value 2;
+        ] ;
+    ];
+
+    rdfs:comment """
+A tilt EQ audio filter.
+""" ;
+
+    doap:name "nymph tilt filter" ;
+    doap:license <https://spdx.org/licenses/MIT> ;
+
+    doap:maintainer [
+        foaf:name "Christopher Arndt" ;
+        foaf:mbox <mailto:info@chrisarndt.de> ;
+        foaf:homepage <https://gitlab.com/SpotlightKid/nymph> ;
+    ] ;
+
+    lv2:microVersion 0 ;
+    lv2:minorVersion 1 .
+

examples/tiltfilter.nim

@@ -0,0 +1,165 @@
+##
+## Tilt Filter
+##
+## Nim translation of this Rust implementation:
+##
+## https://github.com/ardura/Actuate/blob/main/src/fx/ArduraFilter.rs
+##
+## Inspired by https://www.musicdsp.org/en/latest/Filters/267-simple-tilt-equalizer.html
+## Lowpass, Bandpass, Highpass based off tilt filter code
+
+import math
+
+const
+    slopeNeg = -60.0
+    amp = 6.0 / ln(2.0)
+    denorm = pow(10.0, -30.0)
+    minFreq = 20.0
+    maxFreq = 20_000.0
+
+type
+    FilterMode* = enum
+        fmLowPass, fmBandPass, fmHighPass
+
+    TiltFilter* = object
+        # Filter parameters
+        sampleRate: float64
+        centerFreq: float
+        steepness: float
+        mode: FilterMode
+        # Filter tracking / internal
+        needsUpdate: bool
+        sampleRateX3: float64
+        lowGain: float
+        highGain: float
+        a: float
+        b: float
+        lpOut: float
+        # Band pass separate vars
+        bandALow: float
+        bandBLow: float
+        bandOutLow: float
+        bandAHigh: float
+        bandBHigh: float
+        bandOutHigh: float
+
+
+# Super useful function to scale an sample 0-1 into other ranges
+proc scaleRange(sample, minOutput, maxOutput: float): float =
+    result = clamp(sample * (maxOutput - minOutput) + minOutput, minOutput, maxOutput)
+
+
+proc initTiltFilter*(centerFreq, steepness: float, mode: FilterMode = fmLowPass, sampleRate: float64 = 48_000.0): TiltFilter =
+    let sampleRateX3 = 3.0 * sampleRate
+
+    case mode:
+        # These are the gains for the slopes when math happens later
+        of fmLowPass:
+            result.lowGain = exp(0.0 / amp) - 1.0
+            result.highGain = exp(slopeNeg / amp) - 1.0
+        of fmBandPass:
+            result.lowGain = exp(0.0 / amp) - 1.0
+            result.highGain = exp(slopeNeg / amp) - 1.0
+        of fmHighPass:
+            result.lowGain = exp(slopeNeg / amp) - 1.0
+            result.highGain = exp(0.0 / amp) - 1.0
+
+    let omega = 2.0 * PI * centerFreq
+    let n = 1.0 / (scaleRange(steepness, 0.98, 1.2) * (sampleRateX3 + omega))
+    result.a = 2.0 * omega * n
+    result.bandALow = result.a
+    result.bandAHigh = result.a
+    result.b = (sampleRateX3 - omega) * n
+    result.bandBLow = result.b
+    result.bandBHigh = result.b
+    result.lpOut = 0.0
+    result.bandOutLow = 0.0
+    result.bandOutHigh = 0.0
+    result.centerFreq = centerFreq
+    result.sampleRateX3 = sampleRateX3
+    result.steepness = steepness
+    result.sampleRate = sampleRate
+    result.mode = mode
+    result.needsUpdate = true
+
+
+proc setMode*(self: var TiltFilter, mode: FilterMode) =
+    if mode != self.mode:
+        self.mode = mode
+        self.needsUpdate = true
+
+
+proc setCenterFreq*(self: var TiltFilter, value: float) =
+    let freq = value.clamp(minFreq, maxFreq)
+
+    if freq != self.centerFreq:
+        self.centerFreq = freq
+        self.needsUpdate = true
+
+
+proc setSteepness*(self: var TiltFilter, value: float) =
+    let steepness = value.clamp(0.0, 1.0)
+
+    if steepness != self.steepness:
+        self.steepness = steepness
+        self.needsUpdate = true
+
+
+proc setSampleRate*(self: var TiltFilter, sampleRate: float) =
+    if sampleRate != self.sampleRate:
+        self.sampleRate = sampleRate
+        self.sampleRateX3 = self.sampleRate * 3.0
+        self.needsUpdate = true
+
+
+proc reset*(self: var TiltFilter) =
+    discard
+
+
+proc update*(self: var TiltFilter) =
+    if self.needsUpdate:
+        case self.mode:
+            of fmLowPass:
+                let omega = 2.0 * PI * self.centerFreq
+                let n = 1.0 / (scaleRange(self.steepness, 0.98, 1.2) * (self.sample_rate_x3 + omega))
+                self.b = (self.sampleRateX3 - omega) * n
+                self.lowGain = exp(0.0 / amp) - 1.0
+                self.highGain = exp(slopeNeg / amp) - 1.0
+            of fmBandPass:
+                let width = self.steepness * self.steepness * 500.0
+
+                let lowOmega = 2.0 * PI * (self.centerFreq - width).clamp(20.0, 16_000.0)
+                let lowN = 1.0 / (scaleRange(self.steepness, 0.98, 1.2) * (self.sampleRateX3 + lowOmega))
+                self.bandALow = 2.0 * lowOmega * lowN
+                self.bandBLow = (self.sampleRateX3 - lowOmega) * lowN
+
+                let highOmega = 2.0 * PI * (self.centerFreq + width).clamp(20.0, 16_000.0);
+                let highN = 1.0 / (scaleRange(self.steepness, 0.98, 1.2) * (self.sampleRateX3 + highOmega))
+                self.bandAHigh = 2.0 * highOmega * highN
+                self.bandBHigh = (self.sampleRateX3 - highOmega) * highN
+
+                self.lowGain = exp(0.0 / amp) - 1.0
+                self.highGain = exp(slopeNeg / amp) - 1.0
+            of fmHighPass:
+                let omega = 2.0 * PI * self.centerFreq
+                let n = 1.0 / (scaleRange(self.steepness, 0.98, 1.2) * (self.sampleRateX3 + omega))
+                self.a = 2.0 * omega * n
+                self.b = (self.sampleRateX3 - omega) * n
+                self.lowGain = exp(slopeNeg / amp) - 1.0
+                self.highGain = exp(0.0 / amp) - 1.0
+
+        self.needsUpdate = false
+
+
+##
+## Process the input sample using the tilt filter
+##
+proc process*(self: var TiltFilter, sample: float): float =
+    if self.mode == fmBandPass:
+        self.bandOutLow = self.bandALow * sample + self.bandBLow * self.bandOutLow
+        let temp = sample + self.highGain * self.bandOutLow + self.lowGain * (sample - self.bandOutLow)
+        self.bandOutHigh = self.bandAHigh * temp + self.bandBHigh * self.bandOutHigh
+        result = temp + self.lowGain * self.bandOutHigh + self.highGain * (temp - self.bandOutHigh) + denorm
+    else:
+        self.lpOut = self.a * sample + self.b * self.lpOut;
+        result = sample + self.lowGain * self.lpOut + self.highGain * (sample - self.lpOut) + denorm

examples/tiltfilter_plugin.nim

@@ -0,0 +1,104 @@
+## A tilt EQ / filter LV2 plugin
+
+import nymph
+
+import paramsmooth
+import tiltfilter
+
+const
+    PluginUri = "urn:nymph:examples:tiltfilter"
+    minFreq = 20.0
+    maxFreq = 20_000.0
+
+type
+    SampleBuffer = UncheckedArray[cfloat]
+
+    PluginPort {.pure.} = enum
+        Input, Output, Frequency, Steepness, Mode
+
+    TiltFilterPlugin = object
+        input: ptr SampleBuffer
+        output: ptr SampleBuffer
+        freq: ptr cfloat
+        steepness: ptr cfloat
+        mode: ptr cfloat
+        flt: TiltFilter
+        smoothFreq: ParamSmooth
+
+
+proc instantiate(descriptor: ptr Lv2Descriptor; sampleRate: cdouble;
+                 bundlePath: cstring; features: ptr UncheckedArray[ptr Lv2Feature]):
+                 Lv2Handle {.cdecl.} =
+    try:
+        let plug = createShared(TiltFilterPlugin)
+        plug.flt = initTiltFilter(10_000.0, 1.0, fmLowPass, sampleRate)
+        plug.smoothFreq = initParamSmooth(20.0, sampleRate)
+        return cast[Lv2Handle](plug)
+    except OutOfMemDefect:
+        return nil
+
+
+proc connectPort(instance: Lv2Handle; port: cuint;
+                 dataLocation: pointer) {.cdecl.} =
+    let plug = cast[ptr TiltFilterPlugin](instance)
+    case cast[PluginPort](port)
+    of PluginPort.Input:
+        plug.input = cast[ptr SampleBuffer](dataLocation)
+    of PluginPort.Output:
+        plug.output = cast[ptr SampleBuffer](dataLocation)
+    of PluginPort.Frequency:
+        plug.freq = cast[ptr cfloat](dataLocation)
+    of PluginPort.Steepness:
+        plug.steepness = cast[ptr cfloat](dataLocation)
+    of PluginPort.Mode:
+        plug.mode = cast[ptr cfloat](dataLocation)
+
+
+proc activate(instance: Lv2Handle) {.cdecl.} =
+    let plug = cast[ptr TiltFilterPlugin](instance)
+    plug.flt.reset()
+
+
+proc run(instance: Lv2Handle; nSamples: cuint) {.cdecl.} =
+    let plug = cast[ptr TiltFilterPlugin](instance)
+    let freq = plug.freq[].clamp(minFreq, maxFreq)
+
+    plug.flt.setMode(plug.mode[].clamp(0.0, 2.0).FilterMode)
+    plug.flt.setSteepness(plug.steepness[])
+
+    for pos in 0 ..< nSamples:
+        plug.flt.setCenterFreq(plug.smoothFreq.process(freq))
+        plug.flt.update()
+        plug.output[pos] = plug.flt.process(plug.input[pos])
+
+
+proc deactivate(instance: Lv2Handle) {.cdecl.} =
+    discard
+
+
+proc cleanup(instance: Lv2Handle) {.cdecl.} =
+    freeShared(cast[ptr TiltFilterPlugin](instance))
+
+
+proc extensionData(uri: cstring): pointer {.cdecl.} =
+    return nil
+
+
+proc NimMain() {.cdecl, importc.}
+
+
+proc lv2Descriptor(index: cuint): ptr Lv2Descriptor {.
+                   cdecl, exportc, dynlib, extern: "lv2_descriptor".} =
+    NimMain()
+
+    if index == 0:
+        result = createShared(Lv2Descriptor)
+        result.uri = cstring(PluginUri)
+        result.instantiate = instantiate
+        result.connectPort = connectPort
+        result.activate = activate
+        result.run = run
+        result.deactivate = deactivate
+        result.cleanup = cleanup
+        result.extensionData = extensionData
+

nymph.nimble

@@ -26,7 +26,8 @@ type Example = tuple
 const examples = to_table({
     "amp": "urn:nymph:examples:amp",
     "miditranspose": "urn:nymph:examples:miditranspose",
-    "multimodefilter": "urn:nymph:examples:multimode-filter",
+    "multimodefilter": "urn:nymph:examples:multimodefilter",
+    "tiltfilter": "urn:nymph:examples:tiltfilter",
 })