@audio/shift-sample

Sampler-style pitch shift — sinc-interpolated fractional-stride resample (no time preservation)

npm install @audio/shift-sample

import sample from '@audio/shift-sample'

Playback-rate pitch shift. Hann-windowed sinc interpolation at a fractional read-head stepped by ratio per output sample. No time preservation — higher pitch = shorter clip.

sample(instrumentBuffer, { semitones: 7 })
sample(audio, { ratio: 2, sincRadius: 16 })

| Param | Default | | |---|---|---| | sincRadius | 8 | Windowed-sinc half-width (samples) |

Preserves waveform identity (literally the same audio, faster/slower), formants — everything scales together. Destroys time: output duration = input_length / ratio, zero-padded to match API.

| f0 err | THD% | alias | attack corr | formant dist | phase coh | shift | |-------:|-----:|------:|------------:|-------------:|----------:|------:| | 2.50 | 0.1 | 0.007 | 0.951 | 2.330 | 0.170 | 1.614 |

Phase coh 0.170 because the modulation rate itself shifts with the pitch (a 5 Hz tremolo becomes 7.5 Hz at ratio 1.5). This is correct behavior for a sampler — not an artifact.

Use when: Instrument one-shots, ROM-sample playback, tracker-style. Not for: Time-preserving pitch shift.

Stream

let write = sample({ ratio: 1.5 })
let out = write(inputBlock)
let tail = write()  // flush

sample buffers the whole input; write(chunk) accumulates and the batch algorithm runs once on write() (flush, no argument), returning everything at once.

Data

Input is a Float32Array (mono) or an array of Float32Array channels ([left, right, ...]) — anything else throws TypeError. ratio also accepts a function t => ratio (seconds from stream start) or a Float32Array breakpoint envelope (resampled across the input via ratioDuration, default the input's own duration) for time-varying pitch.

Part of @audio/shift — the shift family umbrella. This README is generated from the umbrella docs.

MIT © audiojs