rodio/source/
chirp.rs

1//! Chirp/sweep source.
2
3use std::{f32::consts::TAU, time::Duration};
4
5use crate::Source;
6
7/// Convenience function to create a new `Chirp` source.
8#[inline]
9pub fn chirp(
10    sample_rate: cpal::SampleRate,
11    start_frequency: f32,
12    end_frequency: f32,
13    duration: Duration,
14) -> Chirp {
15    Chirp::new(sample_rate, start_frequency, end_frequency, duration)
16}
17
18/// Generate a sine wave with an instantaneous frequency that changes/sweeps linearly over time.
19/// At the end of the chirp, once the `end_frequency` is reached, the source is exhausted.
20#[derive(Clone, Debug)]
21pub struct Chirp {
22    start_frequency: f32,
23    end_frequency: f32,
24    sample_rate: cpal::SampleRate,
25    total_samples: u64,
26    elapsed_samples: u64,
27}
28
29impl Chirp {
30    fn new(
31        sample_rate: cpal::SampleRate,
32        start_frequency: f32,
33        end_frequency: f32,
34        duration: Duration,
35    ) -> Self {
36        Self {
37            sample_rate,
38            start_frequency,
39            end_frequency,
40            total_samples: (duration.as_secs_f64() * (sample_rate.0 as f64)) as u64,
41            elapsed_samples: 0,
42        }
43    }
44}
45
46impl Iterator for Chirp {
47    type Item = f32;
48
49    fn next(&mut self) -> Option<Self::Item> {
50        let i = self.elapsed_samples;
51        let ratio = self.elapsed_samples as f32 / self.total_samples as f32;
52        self.elapsed_samples += 1;
53        let freq = self.start_frequency * (1.0 - ratio) + self.end_frequency * ratio;
54        let t = (i as f32 / self.sample_rate() as f32) * TAU * freq;
55        Some(t.sin())
56    }
57}
58
59impl Source for Chirp {
60    fn current_frame_len(&self) -> Option<usize> {
61        None
62    }
63
64    fn channels(&self) -> u16 {
65        1
66    }
67
68    fn sample_rate(&self) -> u32 {
69        self.sample_rate.0
70    }
71
72    fn total_duration(&self) -> Option<Duration> {
73        let secs: f64 = self.total_samples as f64 / self.sample_rate.0 as f64;
74        Some(Duration::new(1, 0).mul_f64(secs))
75    }
76}