@audio/weighting-k

ITU-R BS.1770-4 K-weighting — the loudness pre-filter behind LUFS

npm install @audio/weighting-k

import kWeighting from '@audio/weighting-k'

Time-domain K-weighting: two cascaded stages redesigned per sample rate from the canonical ITU-R BS.1770-4 Annex 1 analog prototype constants (De Man 2014, "Evaluation of Implementations of the ITU-R BS.1770 Loudness Algorithm" — the same design pyloudnorm uses). Stage 1 is a spherical-head high shelf (G=3.999843853973347 dB, Q=0.7071752369554196, fc=1681.974450955533 Hz); stage 2 is the RLB weighting highpass (Q=0.5003270373238773, fc=38.13547087602444 Hz, unnormalized {1,-2,1} numerator at any fs). At fs=48000 this reproduces the spec's published coefficient table to ~1e-11.

kWeighting(data)                          // in place, fs=48000
kWeighting(data, { fs: 44100 })
let sos = kWeighting.coefs(44100)         // 2 SOS sections (shelf, then RLB highpass)
kWeighting.response(2000, 48000)          // |H(2000)| — shelf boost

| Param | Default | | |---|---|---| | fs | 48000 | sample rate — SOS recomputed when it changes mid-stream |

| Static | Returns | | |---|---|---| | .coefs(fs) | SOS | 2-section cascade (high shelf + RLB highpass) at rate fs, for analysis/plotting | | .response(f, fs) | number | \|H(f)\| — exact magnitude of this atom's own .coefs(fs) cascade, not an independent approximation |

Use when: implementing integrated/momentary/short-term loudness (LUFS) per ITU-R BS.1770 / EBU R128 — this is the mandated pre-filter, applied before mean-square gating and channel summing.

Part of @audio/weighting — the weighting family umbrella.

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