touches on popgen

code/popgen/Cargo.toml

@@ -9,6 +9,7 @@ path = "src/popgen.rs"
 
 [dependencies]
 clap = { version = "4.5.23", features = ["derive"] }
+hound = "3.5.1"
 rand = "0.8.5"
 regex = "1.11.1"
 rodio = "0.20.1"

code/popgen/src/popgen.rs

@@ -4,9 +4,10 @@
 // https://github.com/pdx-cs-sound/popgen/blob/main/popgen.py
 
 use clap::Parser;
+use hound;
 use rand::Rng;
 use regex::Regex;
-use rodio::{OutputStream, buffer::SamplesBuffer, Sink};
+use rodio::{buffer::SamplesBuffer, OutputStream, Sink};
 use std::{f32::consts::PI, vec};
 
 const C5: &str = "C[5]";
@@ -93,11 +94,10 @@ fn chord_to_note_offset(posn: i8) -> i8 {
     floor_div(posn, 3) * 7 + (major_chord as i8) - 1
 }
 
+// Choose four random notes (one measure) with proper chord offset from the base note
 fn pick_notes(chord_root: u8, position: &mut i8, rng: &mut rand::prelude::ThreadRng) -> [i8; 4] {
     let mut notes: [i8; 4] = [0; 4]; //Vec would work too, but less memory efficient
-
     let mut p: i8 = *position;
-
     for note in &mut notes {
         let chord_note_offset: i8 = chord_to_note_offset(p);
         let chord_note: i8 = note_to_key_offset((chord_root as i8) + chord_note_offset);
@@ -130,6 +130,7 @@ fn parse_note(note_str: &str, regex: Regex) -> u32 {
     let mut it: std::str::Chars<'_> = chars.into_iter();
     let base_note: char = it.next().unwrap();
     let mut flat: bool = false;
+    // Logic to Handle all valid cases, like C, C[4], Db, Db[6], etc.
     match it.next() {
         Some(c) => {
             if c == 'b' {
@@ -155,6 +156,7 @@ fn parse_note(note_str: &str, regex: Regex) -> u32 {
         None => {}
     }
 
+    // Different string format for flat vs not
     let index: usize = match flat {
         true => NAMES.iter().position(|&n| n == format!("{}b", base_note)),
         false => NAMES.iter().position(|&n| n == base_note.to_string()),
@@ -186,27 +188,35 @@ struct Args {
     #[arg(short, long, default_value_t = -3)]
     gain: i8,
 
-    #[arg(short, long, default_value_t = NO_OUTPUT.to_string())]
+    #[arg(short, long, default_value_t = NO_OUTPUT.to_string())] // Ideally there is a better way than this
     output: String,
 }
 
 // Rodio example https://github.com/RustAudio/rodio/blob/master/examples/basic.rs
-fn play(samples: Vec<f32>) {
-
-    let (_stream, stream_handle) =  OutputStream::try_default().unwrap();
-    let source = SamplesBuffer::new(1,48_000, samples);
-
-    let sink = Sink::try_new(&stream_handle).unwrap();
-
+fn play(samples: Vec<f32>, samplerate: u16, gain: i8) {
+    // TODO: apply gain
+    let (_stream, stream_handle) = OutputStream::try_default().unwrap();
+    let source: SamplesBuffer<f32> = SamplesBuffer::new(1, samplerate as u32, samples);
+    let sink: Sink = Sink::try_new(&stream_handle).unwrap(); //sink makes it easy to keep the program asleep so the whole song plays
     sink.append(source);
-
     sink.sleep_until_end();
+}
 
-
+fn save(samples: Vec<f32>, samplerate: u16, output: &str, gain: i8) {
+    // TODO: apply gain
+    let spec: hound::WavSpec = hound::WavSpec {
+        channels: 1,
+        sample_rate: samplerate as u32,
+        bits_per_sample: 32,
+        sample_format: hound::SampleFormat::Float,
+    };
+    let mut writer = hound::WavWriter::create(output, spec).unwrap();
+    for s in samples {
+        writer.write_sample(s).unwrap();
+    }
 }
 
 fn main() {
-    println!("Hello, pop!");
     let args: Args = Args::parse();
     let note_name_regexp: Regex = Regex::new(REGEX_BASE).unwrap();
     let mut rng: rand::prelude::ThreadRng = rand::thread_rng();
@@ -235,35 +245,43 @@ fn main() {
     let mut sound: Vec<f32> = vec![];
 
     for chord_root in CHORD_LOOP {
-        let notes = pick_notes(chord_root - 1, &mut position, &mut rng);
+        let notes: [i8; 4] = pick_notes(chord_root - 1, &mut position, &mut rng);
 
         let mut melody: Vec<Vec<f32>> = vec![];
         for note in notes {
-            let melody_note: Vec<f32> = make_note(note +melody_root_i8 , None, beat_samples, samplerate);
+            let melody_note: Vec<f32> =
+                make_note(note + melody_root_i8, None, beat_samples, samplerate);
             melody.push(melody_note);
         }
 
         let bass_note: i8 = note_to_key_offset((chord_root - 1) as i8);
         let bass: Vec<f32> = make_note(bass_note + bass_root, Some(4), beat_samples, samplerate);
-        let bass_gain = 1 - melody_gain;
-        
-        // Scale the waveforms
+        let bass_gain: i8 = 1 - melody_gain;
+
+        // Unlike pythons array arithmetic, here we must unravel and mutate our data structures to apply the gains in the correct place.
         let flattened_melody: Vec<f32> = melody.into_iter().flatten().collect();
-        let scaled_melody: Vec<f32> = flattened_melody.iter().map(|&x| x * melody_gain as f32).collect();
+
+        let scaled_melody: Vec<f32> = flattened_melody
+            .iter()
+            .map(|&x| x * melody_gain as f32)
+            .collect();
         let scaled_bass: Vec<f32> = bass.iter().map(|&x| x * bass_gain as f32).collect();
 
-        let paired_notes: Vec<(f32, f32)> = scaled_melody.iter().zip(scaled_bass.iter()).map(|(&m, &b)| (m, b)).collect();
+        let paired_notes: Vec<(f32, f32)> = scaled_melody
+            .iter()
+            .zip(scaled_bass.iter())
+            .map(|(&m, &b)| (m, b))
+            .collect();
 
+        // Finally, combine back together
         let combined_waveform: Vec<f32> = paired_notes.iter().map(|(m, b)| m + b).collect();
 
         sound.extend(combined_waveform);
-
     }
     if args.output.eq(NO_OUTPUT) {
-        play(sound);
-    }
-    else {
-        todo!()
+        play(sound, samplerate, args.gain);
+    } else {
+        save(sound, samplerate, &args.output, args.gain);
     }
 }