5 twiddle: Vec<FFTComplex>,
12 fn imdct(src: &[f32], dst: &mut [f32], length: usize) {
13 for n in 0..length*2 {
16 dst[n] += src[k] * (consts::PI / (length as f32) * ((n as f32) + 0.5 + ((length/2) as f32)) * ((k as f32) + 0.5)).cos();
22 pub fn new(mode: FFTMode, size: usize) -> Self {
23 let mut twiddle: Vec<FFTComplex> = Vec::with_capacity(size / 4);
24 let factor = 2.0 * consts::PI / ((8 * size) as f32);
26 twiddle.push(FFTComplex::exp(factor * ((8 * k + 1) as f32)));
28 let fft = FFTBuilder::new_fft(mode, size/4);
29 let mut z: Vec<FFTComplex> = Vec::with_capacity(size / 2);
30 z.resize(size / 2, FFTC_ZERO);
31 IMDCT { twiddle, fft, size, z }
33 pub fn imdct(&mut self, src: &[f32], dst: &mut [f32]) {
34 let size2 = self.size / 2;
35 let size4 = self.size / 4;
36 let size8 = self.size / 8;
38 let c = FFTComplex { re: src[size2 - 2 * k - 1], im: src[ 2 * k] };
39 self.z[k] = c * self.twiddle[k];
41 self.fft.do_fft_inplace(&mut self.z, false);
43 self.z[k] *= self.twiddle[k];
46 dst[ 2 * n] = -self.z[size8 + n] .im;
47 dst[ 2 * n + 1] = self.z[size8 - n - 1].re;
48 dst[ size4 + 2 * n] = -self.z[ n] .re;
49 dst[ size4 + 2 * n + 1] = self.z[size4 - n - 1].im;
50 dst[ size2 + 2 * n] = -self.z[size8 + n] .re;
51 dst[ size2 + 2 * n + 1] = self.z[size8 - n - 1].im;
52 dst[3 * size4 + 2 * n] = self.z[ n] .im;
53 dst[3 * size4 + 2 * n + 1] = -self.z[size4 - n - 1].re;