84 lines
2.4 KiB
Rust
84 lines
2.4 KiB
Rust
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use rustfft::num_complex::Complex;
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use std::f64;
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use crate::DctNum;
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#[inline(always)]
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pub fn single_twiddle<T: DctNum>(i: usize, fft_len: usize) -> Complex<T> {
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let angle_constant = f64::consts::PI * -2f64 / fft_len as f64;
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let c = Complex::from_polar(1f64, angle_constant * i as f64);
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Complex {
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re: T::from_f64(c.re).unwrap(),
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im: T::from_f64(c.im).unwrap(),
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}
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}
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// Same as above, but only return the real portion, not the imaginary portion
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#[inline(always)]
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pub fn single_twiddle_re<T: DctNum>(i: usize, fft_len: usize) -> T {
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let angle_constant = f64::consts::PI * -2f64 / fft_len as f64;
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let c = (angle_constant * i as f64).cos();
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T::from_f64(c).unwrap()
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}
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// Same as above, but we add 0.5 to 0 before
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#[inline(always)]
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pub fn single_twiddle_halfoffset<T: DctNum>(i: usize, fft_len: usize) -> Complex<T> {
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let angle_constant = f64::consts::PI * -2f64 / fft_len as f64;
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let c = Complex::from_polar(1f64, angle_constant * (i as f64 + 0.5f64));
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Complex {
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re: T::from_f64(c.re).unwrap(),
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im: T::from_f64(c.im).unwrap(),
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}
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}
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#[cfg(test)]
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mod unit_tests {
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use super::*;
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use std::f32;
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use crate::test_utils::fuzzy_cmp;
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#[test]
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fn test_single() {
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let len = 20;
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for i in 0..len {
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let single: Complex<f32> = single_twiddle(i, len);
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let single_inverse: Complex<f32> = single_twiddle(i, len).conj();
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let expected =
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Complex::from_polar(1f32, -2f32 * f32::consts::PI * i as f32 / len as f32);
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let expected_inverse =
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Complex::from_polar(1f32, 2f32 * f32::consts::PI * i as f32 / len as f32);
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assert!(
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fuzzy_cmp(single.re, expected.re, 0.001f32),
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"forwards, i = {}",
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i
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);
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assert!(
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fuzzy_cmp(single.im, expected.im, 0.001f32),
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"forwards, i = {}",
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i
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);
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assert!(
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fuzzy_cmp(single_inverse.re, expected_inverse.re, 0.001f32),
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"inverse, i = {}",
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i
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);
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assert!(
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fuzzy_cmp(single_inverse.im, expected_inverse.im, 0.001f32),
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"inverse, i = {}",
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i
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);
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}
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}
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}
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