export declare class ChannelGainController {
    private baseline;
    private initialized;
    private readonly targetLevel;
    reset(): void;
    process(r: number, g: number, b: number): {
        r: number;
        g: number;
        b: number;
    };
}
export declare class ChromPulseModel {
    private readonly windowSize;
    private rQueue;
    private gQueue;
    private bQueue;
    constructor(windowSize?: number);
    reset(): void;
    process(r: number, g: number, b: number): number;
}
export declare function computeSignalSnrDb(values: number[]): number;
/**
 * Streaming cardiac bandpass: a high-pass at `lowHz` cascaded with a low-pass
 * at `highHz`. Feed one sample per frame via {@link process}.
 */
export declare class Bandpass {
    private readonly hp;
    private readonly lp;
    constructor(sampleRate: number, lowHz?: number, highHz?: number);
    reset(): void;
    process(value: number): number;
}
/**
 * Zero-phase bandpass via forward-backward filtering (filtfilt). Filtering
 * twice in opposite directions cancels the phase response, so beat timing is
 * not shifted by the filter — at the cost of being offline (whole-buffer).
 */
export declare function zeroPhaseBandpass(values: number[], sampleRate: number, lowHz?: number, highHz?: number): number[];
/**
 * In-band spectral SNR (linear): peak power in the cardiac band divided by the
 * band's mean power, via a Hann-windowed DFT evaluated on a coarse frequency
 * grid. ~1 means no usable pulse peak; higher means a clean periodic signal.
 * Used to weight ROIs by quality and to gate HR/HRV display.
 */
export declare function spectralSnr(signal: number[], sampleRate: number, minHz?: number, maxHz?: number): number;
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