knyst 0.5.1

Real time dynamic audio graph and synthesis library
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293

//! SVF filter for all your EQ needs
//!
//! Implemented based on [a technical paper by Andrew Simper, Cytomic, 2013](https://cytomic.com/files/dsp/SvfLinearTrapOptimised2.pdf) also available at <https://cytomic.com/technical-papers/>
//!
use knyst_macro::impl_gen;

use crate as knyst;
use crate::prelude::GenState;
use crate::{Sample, SampleRate};

/// Different supported filter types
#[derive(Clone, Copy, Debug)]
pub enum SvfFilterType {
    #[allow(missing_docs)]
    Low,
    #[allow(missing_docs)]
    High,
    #[allow(missing_docs)]
    Band,
    #[allow(missing_docs)]
    Notch,
    #[allow(missing_docs)]
    Peak,
    #[allow(missing_docs)]
    All,
    #[allow(missing_docs)]
    Bell,
    #[allow(missing_docs)]
    LowShelf,
    #[allow(missing_docs)]
    HighShelf,
}
/// A versatile EQ filter implementation
///
/// Implemented based on [a technical paper by Andrew Simper, Cytomic, 2013](https://cytomic.com/files/dsp/SvfLinearTrapOptimised2.pdf) also available at <https://cytomic.com/technical-papers/>
#[derive(Clone, Debug)]
pub struct SvfFilter {
    ty: SvfFilterType,
    cutoff_freq: Sample,
    q: Sample,
    gain_db: Sample,
    // state
    ic1eq: Sample,
    ic2eq: Sample,
    // coefficients
    a1: Sample,
    a2: Sample,
    a3: Sample,
    m0: Sample,
    m1: Sample,
    m2: Sample,
}

#[impl_gen]
impl SvfFilter {
    #[allow(missing_docs)]
    pub fn new(ty: SvfFilterType, cutoff_freq: Sample, q: Sample, gain_db: Sample) -> Self {
        Self {
            ic1eq: 0.,
            ic2eq: 0.,
            a1: 0.,
            a2: 0.,
            a3: 0.,
            m0: 0.,
            m1: 0.,
            m2: 0.,
            ty,
            cutoff_freq,
            q,
            gain_db,
        }
    }
    /// Set the coefficients for the currently set filter type. `gain_db` is only used for Bell, HighShelf and LowShelf.
    pub fn set_coeffs(&mut self, cutoff: Sample, q: Sample, gain_db: Sample, sample_rate: Sample) {
        match self.ty {
            SvfFilterType::Low => {
                let g = ((std::f64::consts::PI as Sample * cutoff) / sample_rate).tan();
                let k = 1.0 / q;
                self.a1 = 1.0 / (1.0 + g * (g + k));
                self.a2 = g * self.a1;
                self.a3 = g * self.a2;
                self.m0 = 0.;
                self.m1 = 0.;
                self.m2 = 1.;
            }
            SvfFilterType::Band => {
                let g = ((std::f64::consts::PI as Sample * cutoff) / sample_rate).tan();
                let k = 1.0 / q;
                self.a1 = 1.0 / (1.0 + g * (g + k));
                self.a2 = g * self.a1;
                self.a3 = g * self.a2;
                self.m0 = 0.;
                self.m1 = 1.;
                self.m2 = 0.;
            }
            SvfFilterType::High => {
                let g = ((std::f64::consts::PI as Sample * cutoff) / sample_rate).tan();
                let k = 1.0 / q;
                self.a1 = 1.0 / (1.0 + g * (g + k));
                self.a2 = g * self.a1;
                self.a3 = g * self.a2;
                self.m0 = 1.;
                self.m1 = -k;
                self.m2 = -1.;
            }
            SvfFilterType::Notch => {
                let g = ((std::f64::consts::PI as Sample * cutoff) / sample_rate).tan();
                let k = 1.0 / q;
                self.a1 = 1.0 / (1.0 + g * (g + k));
                self.a2 = g * self.a1;
                self.a3 = g * self.a2;
                self.m0 = 1.;
                self.m1 = -k;
                self.m2 = 0.;
            }
            SvfFilterType::Peak => {
                let g = ((std::f64::consts::PI as Sample * cutoff) / sample_rate).tan();
                let k = 1.0 / q;
                self.a1 = 1.0 / (1.0 + g * (g + k));
                self.a2 = g * self.a1;
                self.a3 = g * self.a2;
                self.m0 = 1.;
                self.m1 = -k;
                self.m2 = -2.;
            }
            SvfFilterType::All => {
                let g = ((std::f64::consts::PI as Sample * cutoff) / sample_rate).tan();
                let k = 1.0 / q;
                self.a1 = 1.0 / (1.0 + g * (g + k));
                self.a2 = g * self.a1;
                self.a3 = g * self.a2;
                self.m0 = 1.;
                self.m1 = -2. * k;
                self.m2 = 0.;
            }
            SvfFilterType::Bell => {
                let amp = (10.0 as Sample).powf(gain_db / 40.);
                let g =
                    ((std::f64::consts::PI as Sample * cutoff) / sample_rate).tan() / amp.sqrt();
                let k = 1.0 / (q * amp);
                self.a1 = 1.0 / (1.0 + g * (g + k));
                self.a2 = g * self.a1;
                self.a3 = g * self.a2;
                self.m0 = 1.;
                self.m1 = k * (amp * amp - 1.);
                self.m2 = 0.;
            }
            SvfFilterType::LowShelf => {
                let amp = (10.0 as Sample).powf(gain_db / 40.);
                let g =
                    ((std::f64::consts::PI as Sample * cutoff) / sample_rate).tan() / amp.sqrt();
                let k = 1.0 / q;
                self.a1 = 1.0 / (1.0 + g * (g + k));
                self.a2 = g * self.a1;
                self.a3 = g * self.a2;
                self.m0 = 1.;
                self.m1 = k * (amp - 1.);
                self.m2 = amp * amp - 1.;
            }
            SvfFilterType::HighShelf => {
                let amp = (10.0 as Sample).powf(gain_db / 40.);
                let g =
                    ((std::f64::consts::PI as Sample * cutoff) / sample_rate).tan() * amp.sqrt();
                let k = 1.0 / q;
                self.a1 = 1.0 / (1.0 + g * (g + k));
                self.a2 = g * self.a1;
                self.a3 = g * self.a2;
                self.m0 = amp * amp;
                self.m1 = k * (1. - amp) * amp;
                self.m2 = 1.0 - amp * amp;
            }
        }
    }
    #[allow(missing_docs)]
    pub fn init(&mut self, sample_rate: SampleRate) {
        self.set_coeffs(self.cutoff_freq, self.q, self.gain_db, *sample_rate);
    }
    // TODO: This is vectorisable such that multiple filters can be run at once, e.g. multiple channels with the same coefficients
    #[allow(missing_docs)]
    pub fn process_sample(&mut self, v0: Sample) -> Sample {
        let SvfFilter {
            ic1eq,
            ic2eq,
            a1,
            a2,
            a3,
            m0,
            m1,
            m2,
            ..
        } = self;
        let v3 = v0 - *ic2eq;
        let v1 = *a1 * *ic1eq + *a2 * v3;
        let v2 = *ic2eq + *a2 * *ic1eq + *a3 * v3;
        *ic1eq = 2. * v1 - *ic1eq;
        *ic2eq = 2. * v2 - *ic2eq;

        *m0 * v0 + *m1 * v1 + *m2 * v2
    }
    #[allow(missing_docs)]
    pub fn process(&mut self, input: &[Sample], output: &mut [Sample]) -> GenState {
        for (inp, out) in input.iter().zip(output.iter_mut()) {
            *out = self.process_sample(*inp);
        }
        GenState::Continue
    }
}

/// Svf high shelf filter with controllable settings.
///
/// Uses the [`SvfFilter`] under the hood, but allows for setting the filter parameters at block rate
pub struct SvfHighShelf {
    svf: SvfFilter,
    last_cutoff: Sample,
    last_gain: Sample,
    last_q: Sample,
}
#[impl_gen]
impl SvfHighShelf {
    #[allow(missing_docs)]
    pub fn new() -> Self {
        Self {
            svf: SvfFilter::new(SvfFilterType::HighShelf, 20000., 1.0, 0.0),
            last_cutoff: 20000.,
            last_gain: 0.0,
            last_q: 1.0,
        }
    }
    #[allow(missing_docs)]
    pub fn process(
        &mut self,
        input: &[Sample],
        cutoff_freq: &[Sample],
        gain: &[Sample],
        q: &[Sample],
        output: &mut [Sample],
        sample_rate: SampleRate,
    ) -> GenState {
        if cutoff_freq[0] != self.last_cutoff || gain[0] != self.last_gain || q[0] != self.last_q {
            self.svf
                .set_coeffs(cutoff_freq[0], q[0], gain[0], *sample_rate);
        }
        self.svf.process(input, output);
        GenState::Continue
    }
}

/// Svf filter with controllable settings.
///
/// Uses the [`SvfFilter`] under the hood, but allows for setting the filter parameters at block rate
pub struct SvfDynamic {
    svf: SvfFilter,
    last_cutoff: Sample,
    last_gain: Sample,
    last_q: Sample,
}
#[impl_gen]
impl SvfDynamic {
    #[allow(missing_docs)]
    pub fn new(ty: SvfFilterType) -> Self {
        Self {
            svf: SvfFilter::new(ty, 2000., 1.0, 0.0),
            last_cutoff: 20000.,
            last_gain: 0.0,
            last_q: 1.0,
        }
    }
    #[allow(missing_docs)]
    pub fn process(
        &mut self,
        input: &[Sample],
        cutoff_freq: &[Sample],
        gain: &[Sample],
        q: &[Sample],
        output: &mut [Sample],
        sample_rate: SampleRate,
    ) -> GenState {
        if cutoff_freq[0] != self.last_cutoff || gain[0] != self.last_gain || q[0] != self.last_q {
            // A q value of 0.0 will result in NaN
            let mut safe_q = q[0];
            if safe_q <= 0.0 {
                safe_q = f32::MIN;
            }
            self.svf
                .set_coeffs(cutoff_freq[0], safe_q, gain[0], *sample_rate);
            self.last_cutoff = cutoff_freq[0];
            self.last_gain = gain[0];
            self.last_q = q[0];
        }
        self.svf.process(input, output);
        GenState::Continue
    }
}