Add a simple A440 synth example

examples/simple.rs

@@ -0,0 +1,94 @@
+//!
+//!  simple.rs
+//!
+//!  John Berry <[email protected]>
+//!
+//!  Always remember to run high performance Rust code with the --release flag. `Synth`
+//!
+
+extern crate dsp;
+extern crate pitch_calc as pitch;
+extern crate portaudio;
+extern crate synth;
+
+use dsp::{Node, Settings};
+use pitch::{Letter, LetterOctave};
+use portaudio as pa;
+
+const CHANNELS: i32 = 2;
+const FRAMES: u32 = 64;
+const SAMPLE_HZ: f64 = 44_100.0;
+
+fn main() {
+  run().unwrap()
+}
+
+fn run() -> Result<(), pa::Error> {
+    // Construct the simplest possible synth --
+    // a single voice containing a sine wave oscillating at 440 Hz.
+    let mut synth = {
+        use synth::{Synth, mode};
+
+        // Create an oscillator tuned to C1
+        let waveform = synth::oscillator::waveform::Sine;
+        let amp = 1.0;
+        let hz = LetterOctave(Letter::C, 1).hz() as f64;
+        let freq_warp = ();
+        let oscillator = synth::Oscillator::new(waveform, amp, hz, freq_warp);
+
+        // Set up our synth using the oscillator and a single voice, based at C1
+        Synth::new(mode::Mono::retrigger(), ())
+            .oscillator(oscillator)
+            .duration(6000.0)
+            .base_pitch(LetterOctave(Letter::C, 1).hz())
+            .fade(500.0, 500.0)
+            .num_voices(1)
+            .volume(0.20)
+    };
+
+    // Trigger the synth at A4 (440 Hz)
+    let note = LetterOctave(Letter::A, 4);
+    let note_velocity = 1.0;
+    synth.note_on(note, note_velocity);
+
+    // These variables are used to break the audio loop after four seconds
+    let note_duration = 4.0;
+    let mut is_note_off = false;
+    let mut timer: f64 = 0.0;
+    let mut prev_time = None;
+
+    // This callback gets passed to our stream
+    let callback = move |pa::OutputStreamCallbackArgs { buffer, frames, time, .. }| {
+        dsp::sample::buffer::equilibrium(buffer);
+        let settings = Settings::new(SAMPLE_HZ as u32, frames as u16, CHANNELS as u16);
+        synth.audio_requested(buffer, settings);
+        if timer < 6.0 {
+            let last_time = prev_time.unwrap_or(time.current);
+            let dt = time.current - last_time;
+            timer += dt;
+            prev_time = Some(time.current);
+
+            // Break if we've exceeded the desired note duration
+            if timer > note_duration {
+                if !is_note_off {
+                    synth.note_off(note);
+                    is_note_off = true;
+                }
+            }
+            pa::Continue
+        } else {
+            pa::Complete
+        }
+    };
+
+    // Set up PortAudio and the stream
+    let pa = try!(pa::PortAudio::new());
+    let settings = try!(pa.default_output_stream_settings::<f32>(CHANNELS, SAMPLE_HZ, FRAMES));
+    let mut stream = try!(pa.open_non_blocking_stream(settings, callback));
+    try!(stream.start());
+
+    // Loop while the stream is active
+    while let Ok(true) = stream.is_active() {}
+
+    Ok(())
+}