Add multi-mode state-variable filter example plugin
Signed-off-by: Christopher Arndt <chris@chrisarndt.de>
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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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a lv2:Plugin ;
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lv2:binary <libmultimode_filter.so> ;
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rdfs:seeAlso <multimode_filter.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 unit: <http://lv2plug.in/ns/extensions/units#> .
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<urn:nymph:examples:multimode-filter>
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a lv2:Plugin, lv2:AmplifierPlugin , 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 7000.0 ;
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lv2:minimum 16.0 ;
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lv2:maximum 7000.0 ;
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lv2:portProperty props:logarithmic;
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unit:unit unit: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 "Q" ;
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lv2:symbol "q" ;
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lv2:default 0.8 ;
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lv2:minimum 0.8 ;
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lv2:maximum 10.0 ;
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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 3 ;
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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:label "Bandreject" ;
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rdf:value 3 ;
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] ;
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];
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rdfs:comment """
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A multi-mode (LPF/HPF/BPF/Notch) audio filter.
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""" ;
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doap:name "nymph multi-mode 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 +1,97 @@
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## A simple multi-mode audio filter LV2 plugin
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import nymph
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import svf
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const PluginUri = "urn:nymph:examples:multimode-filter"
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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, Cutoff, Q, Mode
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SVFPlugin = object
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input: ptr SampleBuffer
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output: ptr SampleBuffer
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cutoff: ptr cfloat
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q: ptr cfloat
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mode: ptr cfloat
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svf: FilterSV
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proc instantiate(descriptor: ptr Lv2Descriptor; sampleRate: cdouble;
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bundlePath: cstring; features: ptr ptr Lv2Feature):
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Lv2Handle {.cdecl.} =
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var plug = createShared(SVFPlugin)
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plug.svf = initFilterSV(fmLowPass, sampleRate)
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return plug
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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 SVFPlugin](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.Cutoff:
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plug.cutoff = cast[ptr cfloat](dataLocation)
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of PluginPort.Q:
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plug.q = 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 SVFPlugin](instance)
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plug.svf.reset()
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plug.svf.setMode(fmLowPass)
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plug.svf.setCutoff(7_000.0)
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plug.svf.setQ(0.8)
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plug.svf.calcCoef()
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proc run(instance: Lv2Handle; nSamples: cuint) {.cdecl.} =
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let plug = cast[ptr SVFPlugin](instance)
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plug.svf.setMode(plug.mode[].int.clamp(0, 4).FilterMode)
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plug.svf.setCutoff(plug.cutoff[].clamp(16.0, 7_000.0))
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plug.svf.setQ(plug.q[].clamp(0.8, 10.0))
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plug.svf.calcCoef()
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for pos in 0 ..< nSamples:
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plug.output[pos] = plug.svf.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 SVFPlugin](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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## State Variable Filter after Hal Chamberlin, Musical Applications of Microprocessors
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## Only stable up to fc ~= fs / 6.5 !
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import std/math
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type
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FilterMode* = enum
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fmLowPass, fmHighPass, fmBandPass, fmBandReject
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FilterSV* = object
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mode: FilterMode
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cutoff: float
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q: float
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lowPass: float
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hiPass: float
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bandPass: float
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bandReject: float
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a: float
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b: float
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maxCutoff: float
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sampleRate: float
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needs_update: bool
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proc reset*(self: var FilterSV) =
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self.lowPass = 0
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self.hiPass = 0
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self.bandPass = 0
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self.bandReject = 0
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proc initFilterSV*(mode: FilterMode = fmLowPass, sampleRate: float = 48_000): FilterSV =
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result.mode = mode
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result.sampleRate = sampleRate
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result.reset()
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result.a = 0
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result.b = 0
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result.maxCutoff = sampleRate / 6.0
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result.needs_update = true
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proc calcCoef*(self: var FilterSV) =
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if self.needs_update:
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self.a = 2.0 * sin(PI * self.cutoff / self.sampleRate)
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if self.q > 0.0:
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self.b = 1.0 / self.q
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else:
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self.b = 0.0
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self.needs_update = false
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proc setCutoff*(self: var FilterSV, cutoff: float) =
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let fc = if cutoff > self.maxCutoff: self.maxCutoff else: cutoff
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if fc != self.cutoff:
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self.cutoff = fc
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self.needs_update = true
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proc setQ*(self: var FilterSV, q: float) =
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if q != self.q:
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self.q = q
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self.needs_update = true
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proc setMode*(self: var FilterSV, mode: FilterMode) =
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self.mode = mode
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proc setSampleRate*(self: var FilterSV, sampleRate: float) =
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if sampleRate != self.sampleRate:
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self.sampleRate = sampleRate
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self.needs_update = true
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self.reset()
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self.calcCoef()
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proc process*(self: var FilterSV, sample: float): float =
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self.lowPass += self.a * self.bandPass
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self.hiPass = sample - (self.lowPass + (self.b * self.bandPass))
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self.bandPass += self.a * self.hiPass
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self.bandReject = self.hiPass + self.lowPass
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case self.mode:
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of fmLowPass:
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return self.lowPass
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of fmHighPass:
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return self.hiPass
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of fmBandPass:
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return self.bandPass
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of fmBandReject:
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return self.bandReject
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@ -24,7 +24,8 @@ type Example = tuple
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const examples = to_table({
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"amp": "urn:nymph:examples:amp"
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"amp": "urn:nymph:examples:amp",
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"multimode_filter": "urn:nymph:examples:multimode-filter",
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})
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