Struct Stft 

pub struct Stft { /* private fields */ }

A planned STFT. It computes one frame at a time into a buffer it owns, so a long stem never holds its whole spectrogram in memory.

The transform is not normalised: a frame holds X[m, k] = sum_n w[n] x[m hop - N/2 + n] exp(-j 2 pi k n / (p N)).

use sound_to_patch::audio::SampleRate;
use sound_to_patch::dsp::{Stft, StftParams};

let rate = SampleRate::new(8_000)?;
let params = StftParams::new(256)?;
let mut stft = Stft::new(params);
let signal: Vec<f64> = (0..1_000).map(|n| (0.1 * f64::from(n)).sin()).collect();
assert_eq!(params.frame_count(signal.len()), 16);
let peak = stft
    .frame(&signal, 8)
    .iter()
    .enumerate()
    .max_by(|a, b| a.1.norm().total_cmp(&b.1.norm()))
    .map(|(bin, _)| bin);
// 0.1 rad per sample is 127.3 Hz at 8 kHz: bin 4 of 31.25 Hz.
assert_eq!(peak, Some(4));

Implementations

impl Stft

pub fn new(params: StftParams) -> Self

Plans the FFT and the window for these parameters.

pub fn params(&self) -> StftParams

Returns the parameters.

pub fn frame(&mut self, samples: &[f64], frame: usize) -> &[Complex64]

Computes frame m of samples and returns its bins() complex values. A frame past the end holds only padding.

pub fn frames(&mut self, samples: &[f64]) -> Vec<Vec<Complex64>>

Computes every frame of samples. Holds the whole spectrogram, so use it for short signals; iterate with Stft::frame otherwise.

Trait Implementations

impl Debug for Stft

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.