implemented Simper SVF and refactored node_sfilter.rs

src/dsp/helpers.rs

@@ -927,6 +927,7 @@ const FILTER_OVERSAMPLE_HAL_CHAMBERLIN : usize = 2;
 /// otherwise the filter becomes unstable.
 /// * `res`  - Resonance from 0.0 to 0.99. Resonance of 1.0 is not recommended,
 /// as the filter will then oscillate itself out of control.
+/// * `israte` - 1.0 divided by the sampling rate (eg. 1.0 / 44100.0).
 /// * `band` - First state variable, containing the band pass result
 /// after processing.
 /// * `low` - Second state variable, containing the low pass result
@@ -973,6 +974,73 @@ pub fn process_hal_chamberlin_svf(
     (high, notch)
 }
 
+/// This function processes a Simper SVF. It's a much newer algorithm
+/// for filtering and provides easy to calculate multiple outputs.
+///
+/// * `input` - Input sample.
+/// * `freq` - Frequency in Hz.
+/// otherwise the filter becomes unstable.
+/// * `res`  - Resonance from 0.0 to 0.99. Resonance of 1.0 is not recommended,
+/// as the filter will then oscillate itself out of control.
+/// * `israte` - 1.0 divided by the sampling rate (eg. 1.0 / 44100.0).
+/// * `band` - First state variable, containing the band pass result
+/// after processing.
+/// * `low` - Second state variable, containing the low pass result
+/// after processing.
+///
+/// This function returns the low pass, band pass and high pass signal.
+/// For a notch or peak filter signal, please consult the following example:
+///
+///```
+///    use hexodsp::dsp::helpers::*;
+///
+///    let samples   = vec![0.0; 44100];
+///    let mut ic1eq = 0.0;
+///    let mut ic2eq = 0.0;
+///    let mut freq  = 1000.0;
+///
+///    for s in samples.iter() {
+///        let (low, band, high) =
+///            process_simper_svf(
+///                *s, freq, 0.5, 1.0 / 44100.0, &mut ic1eq, &mut ic2eq);
+///
+///        // You can easily calculate the notch and peak results too:
+///        let notch = low + high;
+///        let peak  = low - high;
+///        // ... do something with the result here.
+///    }
+///```
+// Simper SVF taken from baseplug (Rust crate) example svf_simper.rs:
+// implemented from https://cytomic.com/files/dsp/SvfLinearTrapOptimised2.pdf
+// thanks, andy!
+#[inline]
+pub fn process_simper_svf(
+    input: f64, freq: f64, res: f64, israte: f64, ic1eq: &mut f64, ic2eq: &mut f64
+) -> (f64, f64, f64) {
+    let g = (std::f64::consts::PI * freq * israte).tan();
+    let k = 2f64 - (1.9f64 * res);
+
+    let a1 = 1.0 / (1.0 + (g * (g + k)));
+    let a2 = g * a1;
+    let a3 = g * a2;
+
+    let v3 = input - *ic2eq;
+    let v1 = (a1 * *ic1eq) + (a2 * v3);
+    let v2 = *ic2eq + (a2 * *ic1eq) + (a3 * v3);
+
+    *ic1eq = (2.0 * v1) - *ic1eq;
+    *ic2eq = (2.0 * v2) - *ic2eq;
+
+    // low   = v2
+    // band  = v1
+    // high  = input - k * v1 - v2
+    // notch = low + high            = input - k * v1
+    // peak  = low - high            = 2 * v2 - input + k * v1
+    // all   = low + high - k * band = input - 2 * k * v1
+
+    (v2, v1, input - k * v1 - v2)
+}
+
 // translated from Odin 2 Synthesizer Plugin
 // Copyright (C) 2020 TheWaveWarden
 // under GPLv3 or any later

src/dsp/mod.rs

@@ -583,7 +583,7 @@ macro_rules! node_list {
                (0  inp   n_id      d_id  r_id   f_def stp_d -1.0, 1.0, 0.0)
                (1 freq  n_pit      d_pit r_fq  f_freq  stp_d -1.0, 0.5647131, 1000.0)
                (2  res   n_id      d_id  r_id   f_def stp_d 0.0, 0.99, 0.5)
-               {3 0 ftype setting(0) fa_sfilter_type 0 7}
+               {3 0 ftype setting(8) fa_sfilter_type 0 12}
                [0 sig],
             test => Test UIType::Generic UICategory::IOUtil
                (0 f     n_id      d_id   r_id   f_def stp_d 0.0, 1.0, 0.5)

src/dsp/node_sfilter.rs

@@ -10,6 +10,7 @@ use crate::dsp::helpers::{
     process_1pole_tpt_lowpass,
     process_1pole_tpt_highpass,
     process_hal_chamberlin_svf,
+    process_simper_svf,
 };
 
 #[macro_export]
@@ -24,6 +25,11 @@ macro_rules! fa_sfilter_type { ($formatter: expr, $v: expr, $denorm_v: expr) =>
             5  => "HP 12c",
             6  => "BP 12c",
             7  => "NO 12c",
+            8  => "LP 12s",
+            9  => "HP 12s",
+           10  => "BP 12s",
+           11  => "NO 12s",
+           12  => "PK 12s",
             _  => "?",
         };
     write!($formatter, "{}", s)
@@ -85,9 +91,54 @@ that is limited to max cutoff frequency of 16kHz.
     HP 12c    - High-pass Hal Chamberlin state variable filter (12dB)
     BP 12c    - Band-pass Hal Chamberlin state variable filter (12dB)
     NO 12c    - Notch Hal Chamberlin state variable filter (12dB)
+
+The (Andrew) Simper state variable filter is a newer design.
+
+    LP 12s    - Low-pass Simper state variable filter (12dB)
+    HP 12s    - High-pass Simper state variable filter (12dB)
+    BP 12s    - Band-pass Simper state variable filter (12dB)
+    NO 12s    - Notch Simper state variable filter (12dB)
+    PK 12s    - Peak Simper state variable filter (12dB)
 "#;
 }
 
+macro_rules! process_filter_fun {
+    ($nframes: expr, $inp: expr, $out: ident, $freq: ident, $res: ident,
+     $input: ident, $minfreq: expr, $maxfreq: expr, $block: block) => { {
+        for frame in 0..$nframes {
+            let $input = $inp.read(frame) as f64;
+            let $freq  = denorm::SFilter::freq($freq, frame) as f64;
+            let $freq  = $freq.clamp($minfreq, $maxfreq);
+            let $res   = denorm::SFilter::res($res, frame) as f64;
+            let $res   = $res.clamp(0.0, 0.99);
+            let s = $block;
+            $out.write(frame, s as f32);
+        }
+    } };
+    ($nframes: expr, $inp: expr, $out: ident, $freq: ident, $res: ident,
+     $input: ident, $maxfreq: expr, $block: block) => { {
+        for frame in 0..$nframes {
+            let $input = $inp.read(frame) as f64;
+            let $freq  = denorm::SFilter::freq($freq, frame) as f64;
+            let $freq  = $freq.clamp(1.0, $maxfreq);
+            let $res   = denorm::SFilter::res($res, frame) as f64;
+            let $res   = $res.clamp(0.0, 0.99);
+            let s = $block;
+            $out.write(frame, s as f32);
+        }
+    } };
+    ($nframes: expr, $inp: expr, $out: ident, $freq: ident,
+     $input: ident, $maxfreq: expr, $block: block) => { {
+        for frame in 0..$nframes {
+            let $input = $inp.read(frame) as f64;
+            let $freq  = denorm::SFilter::freq($freq, frame) as f64;
+            let $freq  = $freq.clamp(1.0, $maxfreq);
+            let s = $block;
+            $out.write(frame, s as f32);
+        }
+    } }
+}
+
 impl DspNode for SFilter {
     fn outputs() -> usize { 1 }
 
@@ -125,112 +176,82 @@ impl DspNode for SFilter {
 
         match ftype {
             0 => { // Lowpass
-                for frame in 0..ctx.nframes() {
+                process_filter_fun!(
-                    let input = inp.read(frame) as f64;
+                    ctx.nframes(), inp, out, freq, input, 22000.0, {
-                    let freq = denorm::SFilter::freq(freq, frame) as f64;
-                    let freq = freq.clamp(1.0, 22000.0);
-                    out.write(frame,
                         process_1pole_lowpass(
                             input, freq, self.israte, &mut self.z)
-                        as f32);
+                    })
-                }
             },
             1 => { // Lowpass TPT
-                for frame in 0..ctx.nframes() {
+                process_filter_fun!(
-                    let input = inp.read(frame) as f64;
+                    ctx.nframes(), inp, out, freq, input, 22000.0, {
-                    let freq = denorm::SFilter::freq(freq, frame) as f64;
-                    let freq = freq.clamp(1.0, 22000.0);
-                    out.write(frame,
                         process_1pole_tpt_lowpass(
                             input, freq, self.israte, &mut self.z)
-                        as f32);
+                    })
-                }
             },
             2 => { // Highpass
-                for frame in 0..ctx.nframes() {
+                process_filter_fun!(
-                    let input = inp.read(frame) as f64;
+                    ctx.nframes(), inp, out, freq, input, 22000.0, {
-                    let freq = denorm::SFilter::freq(freq, frame) as f64;
-                    let freq = freq.clamp(1.0, 22000.0);
-                    out.write(frame,
                         process_1pole_highpass(
                             input, freq, self.israte, &mut self.z, &mut self.y)
-                        as f32);
+                    })
-                }
             },
             3 => { // Highpass TPT
-                for frame in 0..ctx.nframes() {
+                process_filter_fun!(
-                    let input = inp.read(frame) as f64;
+                    ctx.nframes(), inp, out, freq, input, 22000.0, {
-                    let freq = denorm::SFilter::freq(freq, frame) as f64;
-                    let freq = freq.clamp(1.0, 22000.0);
-                    out.write(frame,
                         process_1pole_tpt_highpass(
                             input, freq, self.israte, &mut self.z)
-                        as f32);
+                    })
-                }
             },
             4 => { // Low Pass Hal Chamberlin SVF
-                for frame in 0..ctx.nframes() {
+                process_filter_fun!(
-                    let input = inp.read(frame) as f64;
+                    ctx.nframes(), inp, out, freq, res, input, 2.0, 16000.0, {
-                    let freq = denorm::SFilter::freq(freq, frame) as f64;
-                    let freq = freq.clamp(2.0, 16000.0);
-                    let res  = denorm::SFilter::res(res, frame) as f64;
-                    let res  = res.clamp(0.0, 0.99);
-
                         let (_high, _notch) =
                             process_hal_chamberlin_svf(
                                 input, freq, res, self.israte,
                                 &mut self.z, &mut self.y);
-
+                        self.y
-                    out.write(frame, self.y as f32);
+                    });
-                }
             },
             5 => { // High Pass Hal Chamberlin SVF
-                for frame in 0..ctx.nframes() {
+                process_filter_fun!(
-                    let input = inp.read(frame) as f64;
+                    ctx.nframes(), inp, out, freq, res, input, 16000.0, {
-                    let freq = denorm::SFilter::freq(freq, frame) as f64;
-                    let freq = freq.clamp(1.0, 16000.0);
-                    let res  = denorm::SFilter::res(res, frame) as f64;
-                    let res  = res.clamp(0.0, 0.99);
-
                         let (high, _notch) =
                             process_hal_chamberlin_svf(
                                 input, freq, res, self.israte,
                                 &mut self.z, &mut self.y);
-
+                        high
-                    out.write(frame, high as f32);
+                    });
-                }
             },
             6 => { // Band Pass Hal Chamberlin SVF
-                for frame in 0..ctx.nframes() {
+                process_filter_fun!(
-                    let input = inp.read(frame) as f64;
+                    ctx.nframes(), inp, out, freq, res, input, 16000.0, {
-                    let freq = denorm::SFilter::freq(freq, frame) as f64;
-                    let freq = freq.clamp(1.0, 16000.0);
-                    let res  = denorm::SFilter::res(res, frame) as f64;
-                    let res  = res.clamp(0.0, 0.99);
-
                         let (_high, _notch) =
                             process_hal_chamberlin_svf(
                                 input, freq, res, self.israte,
                                 &mut self.z, &mut self.y);
-
+                        self.z
-                    out.write(frame, self.z as f32);
+                    });
-                }
             },
             7 => { // Notch Hal Chamberlin SVF
-                for frame in 0..ctx.nframes() {
+                process_filter_fun!(
-                    let input = inp.read(frame) as f64;
+                    ctx.nframes(), inp, out, freq, res, input, 16000.0, {
-                    let freq = denorm::SFilter::freq(freq, frame) as f64;
-                    let freq = freq.clamp(1.0, 16000.0);
-                    let res  = denorm::SFilter::res(res, frame) as f64;
-                    let res  = res.clamp(0.0, 0.99);
-
                         let (_high, notch) =
                             process_hal_chamberlin_svf(
                                 input, freq, res, self.israte,
                                 &mut self.z, &mut self.y);
-
+                        notch
-                    out.write(frame, notch as f32);
+                    });
-                }
+            },
+            8 => { // Simper SVF Low Pass
+                process_filter_fun!(
+                    ctx.nframes(), inp, out, freq, res, input, 22000.0, {
+                        let (low, _band, _high) =
+                            process_simper_svf(
+                                input, freq, res, self.israte,
+                                &mut self.z, &mut self.y);
+                        low
+                    });
             },
             _ => {},
         }

tests/node_sfilter.rs

@@ -552,3 +552,91 @@ fn check_node_sfilter_halsvf_notch() {
             (0, 20), (10, 32), (100, 16), (1000, 20), (4000, 16), (12000, 20)
         ]);
 }
+
+#[test]
+fn check_node_sfilter_simpersvf_lowpass() {
+    let (mut matrix, mut node_exec) = setup_sfilter_matrix();
+
+    // Low Pass Simper SVF @ 1000Hz RES=1.0
+    let fft = fft_with_freq_res_type(&mut matrix, &mut node_exec, 8, 1000.0, 1.0);
+    assert_eq!(
+        avg_fft_freqs(10.0, &[
+            500, 700, 900, 1000, 1500, 2000, 3000, 4000, 12000
+        ], &fft[..]), vec![
+            (0, 20), (500, 20), (700, 50), (900, 110), (1000, 40),
+            (1500, 10), (2000, 0), (3000, 0), (4000, 0)
+        ]);
+
+    // Low Pass Simper SVF @ 1000Hz RES=0.5
+    let fft = fft_with_freq_res_type(&mut matrix, &mut node_exec, 8, 1000.0, 0.5);
+    assert_eq!(
+        avg_fft_freqs(10.0, &[
+            500, 700, 900, 1000, 1500, 2000, 3000, 4000, 12000
+        ], &fft[..]), vec![
+            (0, 10), (500, 10), (700, 20), (900, 10), (1000, 10),
+            (1500, 0), (2000, 0), (3000, 0), (4000, 0)
+        ]);
+
+    // Low Pass Simper SVF @ 1000Hz RES=0.0
+    let fft = fft_with_freq_res_type(&mut matrix, &mut node_exec, 8, 1000.0, 0.0);
+    assert_eq!(
+        avg_fft_freqs(10.0, &[
+            500, 700, 900, 1000, 1500, 2000, 3000, 4000, 12000
+        ], &fft[..]), vec![
+            (0, 10), (500, 10), (700, 10), (900, 0), (1000, 0),
+            (1500, 0), (2000, 0), (3000, 0), (4000, 0)
+        ]);
+
+    // Low Pass Simper SVF @ 4000Hz RES=1.0
+    let fft = fft_with_freq_res_type(&mut matrix, &mut node_exec, 8, 4000.0, 1.0);
+    assert_eq!(
+        avg_fft_freqs(4.0, &[
+            100, 500, 1000, 2000, 3500, 4000, 5000, 6000, 8000, 12000
+        ], &fft[..]), vec![
+            (0, 24), (100, 16), (500, 20), (1000, 20), (2000, 36), (3500, 132),
+            (4000, 80), (5000, 20), (6000, 8), (8000, 0)
+        ]);
+
+    // Low Pass Simper SVF @ 4000Hz RES=0.0
+    let fft = fft_with_freq_res_type(&mut matrix, &mut node_exec, 8, 4000.0, 0.0);
+    assert_eq!(
+        avg_fft_freqs(4.0, &[
+            100, 500, 1000, 2000, 3500, 4000, 5000, 6000, 8000, 12000
+        ], &fft[..]), vec![
+            (0, 20), (100, 12), (500, 16), (1000, 16), (2000, 12), (3500, 8),
+            (4000, 8), (5000, 4), (6000, 4), (8000, 0)
+        ]);
+
+    // Low Pass Simper SVF @ 22050Hz RES=0.0
+    let fft = fft_with_freq_res_type(&mut matrix, &mut node_exec, 8, 22050.0, 0.0);
+    assert_eq!(
+        avg_fft_freqs(8.0, &[100, 1000, 4000, 12000, 16000, 20000, 22050, 22051], &fft[..]), vec![
+            (0, 16), (100, 16), (1000, 16), (4000, 16), (12000, 16),
+            (16000, 16), (20000, 16), (22050, 0)
+        ]);
+
+    // Low Pass Simper SVF @ 22050Hz RES=1.0
+    let fft = fft_with_freq_res_type(&mut matrix, &mut node_exec, 8, 22050.0, 1.0);
+    assert_eq!(
+        avg_fft_freqs(8.0, &[100, 1000, 4000, 12000, 16000, 20000, 22050, 22051], &fft[..]), vec![
+            (0, 8), (100, 16), (1000, 16), (4000, 16), (12000, 16),
+            (16000, 16), (20000, 16), (22050, 0)
+        ]);
+
+    // Low Pass Simper SVF @ 0Hz RES=0.0
+    let fft = fft_with_freq_res_type(&mut matrix, &mut node_exec, 8, 0.0, 0.0);
+    assert_eq!(
+        avg_fft_freqs(4.0, &[10, 100, 1000, 4000, 12000, 22050, 22051], &fft[..]), vec![
+            (0, 0), (10, 0), (100, 0), (1000, 0), (4000, 0), (12000, 0),
+            (22050, 0)
+        ]);
+
+    // Low Pass Simper SVF @ 0Hz RES=1.0
+    let fft = fft_with_freq_res_type(&mut matrix, &mut node_exec, 8, 0.0, 1.0);
+    assert_eq!(
+        avg_fft_freqs(4.0, &[1, 5, 10, 100, 1000, 4000, 12000, 22050, 22051], &fft[..]), vec![
+            (0, 56), (1, 0), (5, 0), (10, 0), (100, 0), (1000, 0),
+            (4000, 0), (12000, 0), (22050, 0)
+        ]);
+}
+