integratedLufs

Computes the program loudness (the number streaming platforms normalize to), following ITU-R BS.1770-4.

integratedLufs(audio: AudioInput, sampleRate: number): number

Arguments

Param	Type	Description
audio	AudioInput	Mono buffer or 2-D array of channels (see below).
sampleRate	number	Input sample rate; must be a positive integer.

AudioInput is Float64Array | Array<number> | Array<Float64Array>. A 1-D input is treated as mono and duplicated to stereo; a 2-D input is treated as the individual channels.

Returns

number — the gated integrated loudness in LUFS (same unit as LKFS). Returns -Infinity for a silent or too-short input (the gate requires at least one 400 ms block to survive).

Algorithm (exactly as BS.1770-4)

1. Resample to the 48 kHz measurement grid (polyphase Kaiser sinc — the K-weight filter coefficients are only valid at 48 kHz).
2. Apply the K-weighting filter per channel: a high-pass at 38 Hz followed by a high-shelf that is flat to 1 kHz and rises to +4 dB above 2 kHz.
3. Compute meanSquare per 400 ms block (75% overlap), then apply the absolute gate (-70 LKFS), then the relative gate (block - gatedLoudness > -10 LU), iterated to convergence.
4. -0.691 + 10 * log10(gatedSum), where gatedSum weights channels [1, 1, 1, 1.41, 1.41] for mono/stereo/LR/LC/Rs.

Examples

import { integratedLufs } from "dsp-audio-metrics";

// Full-scale 1 kHz sine → -3.01
const sr = 48000;
const sine = new Float64Array(sr).map((_, i) =>
  Math.sin((2 * Math.PI * 1000 * i) / sr),
);
integratedLufs(sine, sr); // -3.01...

// 44.1 kHz content is resampled internally
integratedLufs(sine44k, 44100); // agrees with the 48k version within 0.1 LU

Errors

Throws RangeError if sampleRate is not a positive integer, and TypeError for empty input (the loudness of zero samples is undefined).