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feat: add tiltfilter example

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This commit is contained in:
Christopher Arndt 2024-09-27 19:37:02 +02:00
parent 75f3ce03b3
commit f001184fea
10 changed files with 376 additions and 8 deletions
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2
examples/amp.lv2/amp.ttl
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@ -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#> .

2
examples/amp.lv2/manifest.ttl
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@ -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>

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examples/miditranspose.lv2/manifest.ttl
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@ -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>

4
examples/multimodefilter.lv2/manifest.ttl
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@ -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> .

4
examples/multimodefilter.lv2/multimodefilter.ttl
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@ -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#> .

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examples/tiltfilter.lv2/manifest.ttl Normal file
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@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> .

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examples/tiltfilter.lv2/tiltfilter.ttl Normal file
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@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 .

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examples/tiltfilter.nim Normal file
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##
## 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

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## 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

3
nymph.nimble
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@ -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",
})