Improve synth tones example (#784)

examples/synth_tones.rs

@@ -13,54 +13,100 @@ use cpal::{
 use cpal::{FromSample, Sample};
 
 fn main() -> anyhow::Result<()> {
-    let stream = stream_setup_for(sample_next)?;
+    let stream = stream_setup_for()?;
     stream.play()?;
-    std::thread::sleep(std::time::Duration::from_millis(3000));
+    std::thread::sleep(std::time::Duration::from_millis(4000));
     Ok(())
 }
 
-fn sample_next(o: &mut SampleRequestOptions) -> f32 {
-    o.tick();
-    o.tone(440.) * 0.1 + o.tone(880.) * 0.1
-    // combination of several tones
+pub enum Waveform {
+    Sine,
+    Square,
+    Saw,
+    Triangle,
 }
 
-pub struct SampleRequestOptions {
+pub struct Oscillator {
     pub sample_rate: f32,
-    pub sample_clock: f32,
-    pub nchannels: usize,
+    pub waveform: Waveform,
+    pub current_sample_index: f32,
+    pub frequency_hz: f32,
 }
 
-impl SampleRequestOptions {
-    fn tone(&self, freq: f32) -> f32 {
-        (self.sample_clock * freq * 2.0 * std::f32::consts::PI / self.sample_rate).sin()
+impl Oscillator {
+    fn advance_sample(&mut self) {
+        self.current_sample_index = (self.current_sample_index + 1.0) % self.sample_rate;
     }
-    fn tick(&mut self) {
-        self.sample_clock = (self.sample_clock + 1.0) % self.sample_rate;
+
+    fn set_waveform(&mut self, waveform: Waveform) {
+        self.waveform = waveform;
+    }
+
+    fn calculate_sine_output_from_freq(&self, freq: f32) -> f32 {
+        let two_pi = 2.0 * std::f32::consts::PI;
+        (self.current_sample_index * freq * two_pi / self.sample_rate).sin()
+    }
+
+    fn is_multiple_of_freq_above_nyquist(&self, multiple: f32) -> bool {
+        self.frequency_hz * multiple > self.sample_rate / 2.0
+    }
+
+    fn sine_wave(&mut self) -> f32 {
+        self.advance_sample();
+        self.calculate_sine_output_from_freq(self.frequency_hz)
+    }
+
+    fn generative_waveform(&mut self, harmonic_index_increment: i32, gain_exponent: f32) -> f32 {
+        self.advance_sample();
+        let mut output = 0.0;
+        let mut i = 1;
+        while !self.is_multiple_of_freq_above_nyquist(i as f32) {
+            let gain = 1.0 / (i as f32).powf(gain_exponent);
+            output += gain * self.calculate_sine_output_from_freq(self.frequency_hz * i as f32);
+            i += harmonic_index_increment;
+        }
+        output
+    }
+
+    fn square_wave(&mut self) -> f32 {
+        self.generative_waveform(2, 1.0)
+    }
+
+    fn saw_wave(&mut self) -> f32 {
+        self.generative_waveform(1, 1.0)
+    }
+
+    fn triangle_wave(&mut self) -> f32 {
+        self.generative_waveform(2, 2.0)
+    }
+
+    fn tick(&mut self) -> f32 {
+        self.advance_sample();
+        match self.waveform {
+            Waveform::Sine => self.sine_wave(),
+            Waveform::Square => self.square_wave(),
+            Waveform::Saw => self.saw_wave(),
+            Waveform::Triangle => self.triangle_wave(),
+        }
     }
 }
 
-pub fn stream_setup_for<F>(on_sample: F) -> Result<cpal::Stream, anyhow::Error>
+pub fn stream_setup_for() -> Result<cpal::Stream, anyhow::Error>
 where
-    F: FnMut(&mut SampleRequestOptions) -> f32 + std::marker::Send + 'static + Copy,
 {
     let (_host, device, config) = host_device_setup()?;
 
     match config.sample_format() {
-        cpal::SampleFormat::I8 => stream_make::<i8, _>(&device, &config.into(), on_sample),
-        cpal::SampleFormat::I16 => stream_make::<i16, _>(&device, &config.into(), on_sample),
-        // cpal::SampleFormat::I24 => stream_make::<I24, _>(&device, &config.into(), on_sample),
-        cpal::SampleFormat::I32 => stream_make::<i32, _>(&device, &config.into(), on_sample),
-        // cpal::SampleFormat::I48 => stream_make::<I48, _>(&device, &config.into(), on_sample),
-        cpal::SampleFormat::I64 => stream_make::<i64, _>(&device, &config.into(), on_sample),
-        cpal::SampleFormat::U8 => stream_make::<u8, _>(&device, &config.into(), on_sample),
-        cpal::SampleFormat::U16 => stream_make::<u16, _>(&device, &config.into(), on_sample),
-        // cpal::SampleFormat::U24 => stream_make::<U24, _>(&device, &config.into(), on_sample),
-        cpal::SampleFormat::U32 => stream_make::<u32, _>(&device, &config.into(), on_sample),
-        // cpal::SampleFormat::U48 => stream_make::<U48, _>(&device, &config.into(), on_sample),
-        cpal::SampleFormat::U64 => stream_make::<u64, _>(&device, &config.into(), on_sample),
-        cpal::SampleFormat::F32 => stream_make::<f32, _>(&device, &config.into(), on_sample),
-        cpal::SampleFormat::F64 => stream_make::<f64, _>(&device, &config.into(), on_sample),
+        cpal::SampleFormat::I8 => make_stream::<i8>(&device, &config.into()),
+        cpal::SampleFormat::I16 => make_stream::<i16>(&device, &config.into()),
+        cpal::SampleFormat::I32 => make_stream::<i32>(&device, &config.into()),
+        cpal::SampleFormat::I64 => make_stream::<i64>(&device, &config.into()),
+        cpal::SampleFormat::U8 => make_stream::<u8>(&device, &config.into()),
+        cpal::SampleFormat::U16 => make_stream::<u16>(&device, &config.into()),
+        cpal::SampleFormat::U32 => make_stream::<u32>(&device, &config.into()),
+        cpal::SampleFormat::U64 => make_stream::<u64>(&device, &config.into()),
+        cpal::SampleFormat::F32 => make_stream::<f32>(&device, &config.into()),
+        cpal::SampleFormat::F64 => make_stream::<f64>(&device, &config.into()),
         sample_format => Err(anyhow::Error::msg(format!(
             "Unsupported sample format '{sample_format}'"
         ))),
@@ -82,29 +128,44 @@ pub fn host_device_setup(
     Ok((host, device, config))
 }
 
-pub fn stream_make<T, F>(
+pub fn make_stream<T>(
     device: &cpal::Device,
     config: &cpal::StreamConfig,
-    on_sample: F,
 ) -> Result<cpal::Stream, anyhow::Error>
 where
     T: SizedSample + FromSample<f32>,
-    F: FnMut(&mut SampleRequestOptions) -> f32 + std::marker::Send + 'static + Copy,
 {
-    let sample_rate = config.sample_rate.0 as f32;
-    let sample_clock = 0f32;
-    let nchannels = config.channels as usize;
-    let mut request = SampleRequestOptions {
-        sample_rate,
-        sample_clock,
-        nchannels,
+    let num_channels = config.channels as usize;
+    let mut oscillator = Oscillator {
+        waveform: Waveform::Sine,
+        sample_rate: config.sample_rate.0 as f32,
+        current_sample_index: 0.0,
+        frequency_hz: 440.0,
     };
     let err_fn = |err| eprintln!("Error building output sound stream: {}", err);
 
+    let time_at_start = std::time::Instant::now();
+    println!("Time at start: {:?}", time_at_start);
+
     let stream = device.build_output_stream(
         config,
         move |output: &mut [T], _: &cpal::OutputCallbackInfo| {
-            on_window(output, &mut request, on_sample)
+            // for 0-1s play sine, 1-2s play square, 2-3s play saw, 3-4s play triangle_wave
+            let time_since_start = std::time::Instant::now()
+                .duration_since(time_at_start)
+                .as_secs_f32();
+            if time_since_start < 1.0 {
+                oscillator.set_waveform(Waveform::Sine);
+            } else if time_since_start < 2.0 {
+                oscillator.set_waveform(Waveform::Triangle);
+            } else if time_since_start < 3.0 {
+                oscillator.set_waveform(Waveform::Square);
+            } else if time_since_start < 4.0 {
+                oscillator.set_waveform(Waveform::Saw);
+            } else {
+                oscillator.set_waveform(Waveform::Sine);
+            }
+            process_frame(output, &mut oscillator, num_channels)
         },
         err_fn,
         None,
@@ -113,13 +174,17 @@ where
     Ok(stream)
 }
 
-fn on_window<T, F>(output: &mut [T], request: &mut SampleRequestOptions, mut on_sample: F)
-where
-    T: Sample + FromSample<f32>,
-    F: FnMut(&mut SampleRequestOptions) -> f32 + std::marker::Send + 'static,
+fn process_frame<SampleType>(
+    output: &mut [SampleType],
+    oscillator: &mut Oscillator,
+    num_channels: usize,
+) where
+    SampleType: Sample + FromSample<f32>,
 {
-    for frame in output.chunks_mut(request.nchannels) {
-        let value: T = T::from_sample(on_sample(request));
+    for frame in output.chunks_mut(num_channels) {
+        let value: SampleType = SampleType::from_sample(oscillator.tick());
+
+        // copy the same value to all channels
         for sample in frame.iter_mut() {
             *sample = value;
         }