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extern crate dft;
#[derive(Clone, Debug)]
pub struct FrequencyBucket {
pub min_freq: f64,
pub max_freq: f64,
pub intensity: f64
}
pub fn fft(input: Vec<f64>, sample_rate: f64) -> Vec<FrequencyBucket> {
let frames = input.len();
let plan = dft::Plan::new(dft::Operation::Forward, frames);
let mut intensities = input.clone();
dft::transform(&mut intensities, &plan);
let frequency_resolution = sample_rate / 2.0 / frames as f64;
intensities.iter().enumerate().map(|(index, &value)| {
let index = index as f64;
FrequencyBucket {
min_freq: index * frequency_resolution,
max_freq: (index+1.0) * frequency_resolution,
intensity: value
}
}).collect()
}
#[test]
fn fft_on_sine_wave() {
use std::f64::consts;
let sample_rate = 44100.0 as f64;
let amplitude = 1.0 as f64;
let frames = 16384;
let frequency = 10000.0 as f64; //10KHz
let samples = (0..frames)
.map(|x| {
let t = x as f64 / sample_rate;
(2.0 as f64 * consts::PI * frequency * t).sin() * amplitude
}).collect();
let result = fft(samples, sample_rate);
let peak = result.iter()
.fold(None as Option<FrequencyBucket>, |max, next|
if max.is_none() || max.clone().unwrap().intensity < next.intensity { Some(next.clone()) } else { max }
).unwrap();
println!("{:?}", peak);
assert!(peak.min_freq <= frequency);
assert!(peak.max_freq >= frequency);
}
pub fn hz_to_pitch(hz: f64) -> String {
let pitch_number = 49.0 + 12.0 * (hz / 440.0).log2();
pitch_number.floor().to_string()
}
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