1 //! A basic output stream example, using an Output AudioUnit to generate a sine wave.
2
3 extern crate coreaudio;
4
5 use coreaudio::audio_unit::{AudioUnit, IOType, SampleFormat};
6 use coreaudio::audio_unit::render_callback::{self, data};
7 use std::f64::consts::PI;
8
9 struct SineWaveGenerator {
10 time: f64,
11 /// generated frequency in Hz
12 freq: f64,
13 /// magnitude of generated signal
14 volume: f64,
15 }
16
17 impl SineWaveGenerator {
new(freq: f64, volume: f64) -> Self18 fn new(freq: f64, volume: f64) -> Self {
19 SineWaveGenerator {
20 time: 0.,
21 freq,
22 volume,
23 }
24 }
25 }
26
27 impl Iterator for SineWaveGenerator {
28 type Item = f32;
next(&mut self) -> Option<f32>29 fn next(&mut self) -> Option<f32> {
30 self.time += 1. / 44_100.;
31 let output = ((self.freq * self.time * PI * 2.).sin() * self.volume) as f32;
32 Some(output)
33 }
34 }
35
main() -> Result<(), coreaudio::Error>36 fn main() -> Result<(), coreaudio::Error> {
37 let frequency_hz = 440.;
38 let volume = 0.15;
39 let mut samples = SineWaveGenerator::new(frequency_hz, volume);
40
41 // Construct an Output audio unit that delivers audio to the default output device.
42 let mut audio_unit = AudioUnit::new(IOType::DefaultOutput)?;
43
44 let stream_format = audio_unit.output_stream_format()?;
45 println!("{:#?}", &stream_format);
46
47 // For this example, our sine wave expects `f32` data.
48 assert!(SampleFormat::F32 == stream_format.sample_format);
49
50 type Args = render_callback::Args<data::NonInterleaved<f32>>;
51 audio_unit.set_render_callback(move |args| {
52 let Args { num_frames, mut data, .. } = args;
53 for i in 0..num_frames {
54 let sample = samples.next().unwrap();
55 for channel in data.channels_mut() {
56 channel[i] = sample;
57 }
58 }
59 Ok(())
60 })?;
61 audio_unit.start()?;
62
63 std::thread::sleep(std::time::Duration::from_millis(3000));
64
65 Ok(())
66 }
67