/**
 * Tap overlay renderer.
 *
 * Takes an mp4 + a list of tap events and renders red rings at each tap
 * position via ffmpeg's drawbox filter. drawbox doesn't draw circles, so
 * we use a hollow square (the standard "tap target" idiom in iOS' built-
 * in "show touches" mode is a circle, but a 4-px-thick red square reads
 * just as well at video scale and avoids needing a generated PNG asset).
 */
export interface OverlayOptions {
    inputPath: string;
    outputPath: string;
    taps: Array<{
        x: number;
        y: number;
        t: number;
    }>;
    /** How long each tap indicator stays on screen in seconds. Default 0.6. */
    durationSec?: number;
    /** Half-side of the indicator square in px. Default 40. */
    radius?: number;
    /** Optional override for the ffmpeg binary; defaults to "ffmpeg" on PATH. */
    ffmpeg?: string;
}
/** Returns true if `ffmpeg` is on PATH. */
export declare function hasFfmpeg(binary?: string): Promise<boolean>;
/**
 * Build the ffmpeg `-vf` filter chain for the given tap events.
 * Pure helper exposed for unit testing.
 */
export declare function buildOverlayFilter(taps: Array<{
    x: number;
    y: number;
    t: number;
}>, durationSec?: number, radius?: number): string;
/**
 * Render `inputPath` → `outputPath` with tap overlays composited at each
 * (x, y, t) coordinate. Throws if ffmpeg fails.
 */
export declare function applyTapOverlays(options: OverlayOptions): Promise<void>;
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