@audio/stretch-pghi

Phase Gradient Heap Integration vocoder — "Phase Vocoder Done Right" (Průša & Holighaus, 2017), causal RTPGHI variant. Synthesis phase is integrated from the analysis phase gradients (instantaneous frequency across time, stretched group delay across frequency), visiting bins in order of decreasing magnitude via a max-heap — phase always flows from strong bins into their neighbourhoods.

No peak picking, no transient heuristics: chirps, vibrato and dense spectra stay coherent by construction.

import pghi from '@audio/stretch-pghi'
let out = pghi(data, { factor: 2 })

| Param | Default | | |---|---|---| | factor | 1 | Time stretch ratio | | frameSize | 2048 | FFT size (power of 2) | | hopSize | frameSize/8 | Hop — gradient integration wants denser frames than peak locking | | tolerance | 1e-6 | Bins below tolerance×max get random phase |

Use when: modulated material — vibrato, glides, chirps, pitch-unstable sources (measured: beats @audio/stretch-pvoc-lock on tones/glissandi, ~4× better than plain pvoc on sweeps). Not for: steady polyphony — identity phase locking reproduces exact intra-region phase relations that first-order gradient integration only approximates; use @audio/stretch-pvoc-lock there.

Part of @audio/stretch.

License

MIT · ॐ