adsr

src/envelope.rs

@@ -1,6 +1,8 @@
 use std::ops::RangeInclusive;
+use std::time::Duration;
 use eframe::egui;
 use eframe::egui::{Context, Id, Label, Slider, Window};
+use rodio::{ChannelCount, SampleRate, Source};
 use serde::{Deserialize, Serialize};
 use crate::gui::Showable;
 
@@ -9,6 +11,7 @@ pub struct Envelope {
     pub attack: f32,
     pub decay: f32,
     pub sustain: f32,
+    pub hold: f32,
     pub release: f32
 }
 
@@ -18,11 +21,92 @@ impl Default for Envelope {
             attack: 0.0,
             decay: 0.0,
             sustain: 1.0,
+            hold: 0.5,
             release: 0.0,
         }
     }
 }
 
+impl Envelope {
+    pub fn modulate<S: Source>(&self, source: S) -> EnvelopeSource<S> {
+        EnvelopeSource {
+            envelope: *self,
+            source,
+            elapsed: 0,
+        }
+    }
+}
+
+pub struct EnvelopeSource<S: Source> {
+    envelope: Envelope,
+    source: S,
+    elapsed: usize
+}
+
+impl<S: Source> Iterator for EnvelopeSource<S> {
+    type Item = f32;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if let Some(val) = self.source.next() {
+            let rate = self.source.sample_rate() as f32; // Number of samples per sec
+            // Which tick are we on (a given tick might be more than one call,
+            // since multiple channels)
+            let mut tick = (self.elapsed / self.source.channels() as usize) as f32;
+            // No matter what happens we have now consumed a sample:
+            self.elapsed += 1;
+
+            // Attack phase:
+            if tick < rate * self.envelope.attack {
+                let m = 1.0 / self.envelope.attack;
+                return Some(val * tick / rate * m)
+            }
+            tick -= rate * self.envelope.attack;
+
+            // Decay phase, reduce to sustain level
+            if tick < rate * self.envelope.decay {
+                let m = (1.0 - self.envelope.sustain) / self.envelope.decay;
+                return Some(val * (1.0 - tick / rate * m))
+            }
+            tick -= rate * self.envelope.decay;
+
+            // Hold phase, hold at sustain level:
+            if tick < rate * self.envelope.hold {
+                return Some(val * self.envelope.sustain)
+            }
+            tick -= rate * self.envelope.hold;
+
+            // Release phase, fade to zero:
+            if tick < rate * self.envelope.release {
+                let m = self.envelope.sustain / self.envelope.release;
+                return Some(val * (self.envelope.sustain - tick / rate * m))
+            }
+
+            None
+        } else {
+            None // Inner sample is done so, so are we
+        }
+    }
+}
+
+impl<S: Source> Source for EnvelopeSource<S> {
+    fn current_span_len(&self) -> Option<usize> {
+        None // Length of the sound
+    }
+
+    fn channels(&self) -> ChannelCount {
+        self.source.channels()
+    }
+
+    fn sample_rate(&self) -> SampleRate {
+        self.source.sample_rate()
+    }
+
+    fn total_duration(&self) -> Option<Duration> {
+        // We don't know right here what the duration is, but it will eventually stop
+        None
+    }
+}
+
 impl Showable<(Id, String)> for (&mut Envelope, &mut bool) {
     fn show(&mut self, ctx: &Context, (id, title): &(Id, String)) {
         let mut open = true;
@@ -43,6 +127,9 @@ impl Showable<(Id, String)> for (&mut Envelope, &mut bool) {
                 ui.add(Label::new("Sustain"));
                 ui.add(Slider::new(&mut self.0.sustain, RangeInclusive::new(0.0, 1.0)));
                 ui.end_row();
+                ui.add(Label::new("Hold"));
+                ui.add(Slider::new(&mut self.0.hold, RangeInclusive::new(0.0, 2.0)));
+                ui.end_row();
                 ui.add(Label::new("Release"));
                 ui.add(Slider::new(&mut self.0.release, RangeInclusive::new(0.0, 1.0)));
                 ui.end_row();
@@ -52,3 +139,125 @@ impl Showable<(Id, String)> for (&mut Envelope, &mut bool) {
         *self.1 = open;
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    struct ConstSource(f32);
+    impl Iterator for ConstSource {
+        type Item = f32;
+        fn next(&mut self) -> Option<Self::Item> {
+            Some(self.0)
+        }
+    }
+    impl Source for ConstSource {
+        fn current_span_len(&self) -> Option<usize> {
+            None
+        }
+
+        fn channels(&self) -> ChannelCount {
+            1
+        }
+
+        fn sample_rate(&self) -> SampleRate {
+            10
+        }
+
+        fn total_duration(&self) -> Option<Duration> {
+            None
+        }
+    }
+
+    fn env(attack: f32, decay: f32, sustain: f32, hold: f32, release: f32) -> Envelope {
+        Envelope {
+            attack, decay, sustain, hold, release
+        }
+    }
+
+    fn assert_close_enough<S: Source>(mut src: S, expected: Vec<f32>) {
+        for e in expected.into_iter() {
+            let val = src.next().unwrap();
+            assert!(val - e < 0.0001)
+        }
+    }
+
+    #[test]
+    fn test_attack() {
+        // Normal: ramp up to 1.0 over 10 samples
+        assert_close_enough(
+            env(1.0, 0.0, 0.0, 0.0, 0.0).modulate(ConstSource(10.0)),
+            vec![0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0]);
+
+        // 0 attack: immediately at 1.0
+        assert_close_enough(
+            env(0.0, 0.0, 1.0, 100.0, 0.0).modulate(ConstSource(10.0)),
+            vec![10.0; 5]);
+    }
+
+    #[test]
+    fn test_decay() {
+        // Ramp down from 1.0 to sustain:
+        assert_close_enough(
+            env(0.0, 0.3, 0.7, 100.0, 0.0).modulate(ConstSource(10.0)),
+            vec![10.0, 9.0, 8.0, 7.0, 7.0, 7.0]);
+
+        // No decay, immediately at sustain:
+        assert_close_enough(
+            env(0.0, 0.0, 0.7, 100.0, 0.0).modulate(ConstSource(10.0)),
+            vec![7.0; 5]);
+
+        // Sustain at 1, stay there:
+        assert_close_enough(
+            env(0.0, 0.5, 1.0, 100.0, 0.0).modulate(ConstSource(10.0)),
+            vec![10.0; 20]);
+
+        // Attack and then decay:
+        // No decay, immediately at sustain:
+        assert_close_enough(
+            env(0.5, 0.3, 0.7, 100.0, 0.0).modulate(ConstSource(10.0)),
+            vec![0.0, 2.0, 4.0, 6.0, 8.0, // 5 samples of attack
+                 10.0, 9.0, 8.0, // three sample decay phase
+                 7.0, 7.0, 7.0, 7.0]); // stuck at sustain
+    }
+
+    #[test]
+    fn test_hold() {
+        // No A/D, hold at sustain for the hold length:
+        assert_close_enough(
+            env(0.0, 0.0, 0.7, 1.0, 0.0).modulate(ConstSource(10.0)),
+            vec![7.0; 10]);
+
+        // It stops holding after the right length (10 hz, 1.0 secs)
+        assert_eq!(
+            env(0.0, 0.0, 0.7, 1.0, 0.0).modulate(ConstSource(10.0)).collect::<Vec<_>>().len(),
+            10
+        );
+    }
+
+    #[test]
+    fn test_release() {
+        // Simple case, release from full
+        assert_close_enough(
+            env(0.0, 0.0, 1.0, 0.0, 1.0).modulate(ConstSource(10.0)),
+            vec![10.0, 9.0, 8.0, 7.0, 6.0, 5.0, 4.0, 3.0, 2.0, 1.0]);
+
+        // Release from sustain
+        assert_close_enough(
+            env(0.0, 0.0, 0.5, 0.0, 1.0).modulate(ConstSource(10.0)),
+            vec![5.0, 4.5, 4.0, 3.5, 3.0, 2.5, 2.0, 1.5, 1.0, 0.5]);
+    }
+
+    #[test]
+    fn test_adsr() {
+        // The entire envelope
+        assert_close_enough(
+            env(0.5, 0.3, 0.7, 0.3, 0.7).modulate(ConstSource(10.0)),
+            vec![
+                0.0, 2.0, 4.0, 6.0, 8.0, // Attack phase
+                10.0, 9.0, 8.0, // Decay phase
+                7.0, 7.0, 7.0, // Hold at sustain
+                7.0, 6.0, 5.0, 4.0, 3.0, 2.0, 1.0 // Release
+            ]);
+    }
+}

src/grid.rs

@@ -33,7 +33,6 @@ impl NoteType {
 pub struct Grid {
     pub note_type: NoteType,
     pub volume: f32,
-    pub length: u64,
     pub scale: Scale,
     pub notes: Vec<bool>,
     pub id: Id,
@@ -48,7 +47,6 @@ impl Grid {
         Self {
             note_type,
             volume: 1.0,
-            length: 250,
             open: true,
             scale: Scale::CMajor,
             notes: vec![false; (LOOP_LENGTH * LOOP_LENGTH) as usize],
@@ -144,10 +142,6 @@ impl Showable<f32> for Grid {
             egui::MenuBar::new().ui(ui, |ui| {
                 ui.label("Volume");
                 ui.add(egui::Slider::new(&mut self.volume, RangeInclusive::new(0.0, 2.0)).show_value(false));
-
-                ui.label("Length");
-                ui.add(egui::Slider::new(&mut self.length, RangeInclusive::new(0, 2000)).show_value(false));
-
             });
 
             egui::Frame::new().inner_margin(3).show(ui, |ui| {

src/noise.rs

@@ -1,7 +1,7 @@
-use std::time::Duration;
 use rodio::mixer::Mixer;
 use rodio::Source;
 use serde::{Deserialize, Serialize};
+use crate::envelope::Envelope;
 
 #[derive(Copy, Clone, Debug, PartialEq, Serialize, Deserialize)]
 pub enum NoteType {
@@ -23,8 +23,8 @@ pub struct Note {
     /// How loud, 0.0 .. 2.0
     pub volume: f32,
 
-    /// How long to fade out
-    pub duration: Duration
+    /// ADSR envelope
+    pub envelope: Envelope
 }
 
 /// The frequency for a given tone, in Hz.
@@ -53,9 +53,8 @@ impl NoteType {
 impl Note {
     pub fn play(self, mixer: &Mixer) {
         let note = self.note_type.source(self.tone);
-        let note = note.fade_out(self.duration);
+        let note = self.envelope.modulate(note);
         let note = note.amplify(self.volume.clamp(0.0, 1.0));
-        let note = note.take_duration(self.duration);
         mixer.add(note)
     }
 }

src/saveload.rs

@@ -34,7 +34,6 @@ impl PersistedTenori {
 struct PersistedGrid {
     note_type: NoteType,
     volume: f32,
-    length: u64,
     scale: Scale,
     notes: String,
     name: String,
@@ -47,7 +46,6 @@ impl From<&Grid> for PersistedGrid {
         Self {
             note_type: value.note_type,
             volume: value.volume,
-            length: value.length,
             scale: value.scale,
             name: value.name.clone(),
             envelope: value.envelope,
@@ -62,7 +60,6 @@ impl PersistedGrid {
         Grid {
             note_type: self.note_type,
             volume: self.volume,
-            length: self.length,
             scale: self.scale,
             name: self.name,
             envelope: self.envelope,

src/tenori.rs

@@ -1,4 +1,4 @@
-use std::time::{Duration, Instant};
+use std::time::Instant;
 use rodio::OutputStream;
 use crate::grid::Grid;
 use crate::dialog::Dialog;
@@ -106,7 +106,7 @@ impl Tenori {
                     note_type: grid.note_type,
                     tone,
                     volume: grid.volume,
-                    duration: Duration::from_millis(grid.length as u64),
+                    envelope: grid.envelope
                 })
             }
         }