/**
 * Loudness and level measurement.
 *
 * ## Why LUFS rather than peak
 *
 * Peak normalisation makes files *the same height*, not the same loudness. A
 * dense pop master and a sparse acoustic recording can share an identical peak
 * and still differ by 10 dB in perceived level — which is why a naive
 * "normalise to 0 dBFS" playlist lurches in volume between tracks.
 *
 * ITU-R BS.1770 measures perceived loudness instead: K-weight the signal
 * (roughly, model the ear's frequency response), take the mean square over
 * overlapping 400 ms blocks, and average the blocks with a two-stage gate that
 * discards silence and quiet passages. EBU R128 builds broadcast practice on
 * top of it, and every streaming platform now normalises this way — Spotify to
 * about -14 LUFS, broadcast to -23.
 *
 * ## True peak
 *
 * Sample peak underreads. The continuous waveform reconstructed at playback can
 * overshoot the highest *sample*, so a file that measures -0.1 dBFS can still
 * clip a listener's DAC or a lossy encoder. True-peak measurement oversamples
 * before measuring, which is what BS.1770 requires and what "-1 dBTP" targets
 * mean.
 */
export interface LoudnessResult {
    /** Integrated (gated) loudness in LUFS. `-Infinity` for digital silence. */
    integrated: number;
    /** Loudness range in LU — the spread between quiet and loud passages. */
    range: number;
    /** Highest 400 ms block loudness, in LUFS. */
    peakMomentary: number;
}
/**
 * Measures integrated loudness per ITU-R BS.1770-4 with EBU R128 gating.
 *
 * @param channels Planar float channels.
 * @param sampleRate Sample rate in Hz.
 */
export declare function measureLoudness(channels: readonly Float32Array[], sampleRate: number): LoudnessResult;
/** Highest absolute sample value across all channels, as a linear ratio. */
export declare function measurePeak(channels: readonly Float32Array[]): number;
/**
 * True-peak level as a linear ratio, via 4x oversampling.
 *
 * BS.1770 specifies at least 4x for rates up to 48 kHz. Inter-sample peaks
 * routinely sit 0.5–1.5 dB above the sample peak on loud material, which is why
 * mastering targets sit at -1 dBTP rather than 0.
 */
export declare function measureTruePeak(channels: readonly Float32Array[]): number;
/** Root-mean-square level across all channels, as a linear ratio. */
export declare function measureRms(channels: readonly Float32Array[]): number;
/** Linear ratio to decibels. Returns `-Infinity` for zero. */
export declare function toDb(linear: number): number;
/** Decibels to linear ratio. */
export declare function fromDb(db: number): number;
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