@audio/shift-ola

OLA (Overlap-Add) pitch shift — simplest stretch+resample baseline

npm install @audio/shift-ola

import ola from '@audio/shift-ola'

Plain OLA time-stretch + sinc resample. Overlap-add without similarity search — the baseline the others improve on.

ola(audio, { ratio: 1.5 })

Preserves amplitude envelope. Destroys pitch accuracy, formants, transients, phase coherence.

| f0 err | THD% | alias | attack corr | formant dist | phase coh | shift | |-------:|-----:|------:|------------:|-------------:|----------:|------:| | 38.33 | 0.2 | 0.004 | 0.980 | 2.342 | 0.995 | 2.025 |

f0 err 38.33 Hz — worst by far. Without similarity search, grains land at arbitrary phase offsets causing destructive interference that shifts the perceived pitch.

Use when: Reference baseline, or the simplest possible shift for comparison. Not for: Anything quality-sensitive.

Stream

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

ola 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 here is a fixed number for the whole call — a function or Float32Array throws.

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

MIT © audiojs