/**
 * Audio mixing chain — EQ, compressor, gate, reverb, de-esser, limiter.
 *
 * File-only path: pure ffmpeg filter strings, mirroring `audio-cleanup.ts`
 * but with parameter knobs the agent can tune per-clip. We expose this as
 * a single "chain" so the agent can express a full mixing decision in one
 * call (e.g. "vocal preset = highpass 80Hz + 3dB peak at 5kHz + 4:1 comp +
 * -1dB ceiling limiter").
 *
 * All filters confirmed present in stock Homebrew ffmpeg:
 *   - equalizer / highpass / lowpass — eq bands
 *   - acompressor — compressor
 *   - agate — gate
 *   - aecho / aphaser — pseudo-reverb
 *   - alimiter — brick-wall limiter
 *   - adynamicequalizer — de-esser (5-9 kHz dynamic shelf)
 *
 * Real-world reference for filter syntax: ffmpeg-filters man page +
 * jiaaro/pydub's effect chains + scottcjn/bottube's mixing helpers.
 */
export interface EqBand {
    /** Filter type. */
    type: "low" | "high" | "peak" | "shelf-low" | "shelf-high";
    /** Center / cutoff frequency in Hz. */
    freqHz: number;
    /** Gain in dB (peak / shelf only; ignored for low/high pass). */
    gainDb?: number;
    /** Bandwidth Q-factor. Default 1. Higher = narrower band. */
    q?: number;
}
export interface Compressor {
    /** Threshold in dB below which the comp doesn't act. -18 to -10 typical for voice. */
    thresholdDb: number;
    /** Ratio. 4 = 4:1 = strong voice control. */
    ratio: number;
    /** Attack in ms. Default 20. */
    attackMs?: number;
    /** Release in ms. Default 250. */
    releaseMs?: number;
    /** Makeup gain in dB. Default 0. */
    makeupDb?: number;
}
export interface Gate {
    /** Below threshold the signal is attenuated. -50 dB cuts most room tone. */
    thresholdDb: number;
    /** Ratio. Higher = more aggressive cut. Default 5. */
    ratio?: number;
    attackMs?: number;
    releaseMs?: number;
}
export interface Reverb {
    /** 0..1; how big the room sounds. */
    roomSize: number;
    /** 0..1; balance. 0 = dry, 1 = all wet. */
    wetDryMix: number;
}
export interface Limiter {
    /** Output ceiling in dB. -1 dBTP is the YouTube/Spotify-friendly default. */
    ceilingDb: number;
    releaseMs?: number;
}
export interface DeEsser {
    /** Frequency in Hz where sibilance lives. Default 6500. */
    freqHz?: number;
    /** Threshold in dB above which the dynamic shelf engages. Default -25. */
    thresholdDb?: number;
}
export interface AudioChain {
    eq?: EqBand[];
    compressor?: Compressor;
    gate?: Gate;
    reverb?: Reverb;
    deess?: DeEsser;
    limiter?: Limiter;
}
/**
 * Build the ffmpeg `-af` filter string for a chain. Pure function — tests
 * verify the full string assembly without spawning ffmpeg.
 *
 * Order: gate → eq → de-esser → compressor → reverb → limiter. This matches
 * the conventional mixing console order: clean noise out first, shape tone,
 * tame dynamics, add ambience, then catch peaks.
 */
export declare function buildMixFilter(chain: AudioChain): string;
/** Apply a mixing chain to one input file. Video stream is copied. */
export declare function applyMix(inputPath: string, outputPath: string, chain: AudioChain, opts?: {
    signal?: AbortSignal;
}): Promise<void>;
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