/**
 * Deterministic, collision-safe cache path for a video's poster frame.
 * A short sha256 prefix of the absolute video path keys the .jpg, so the same
 * video always maps to the same cache file (and distinct videos never collide).
 */
export declare function looseThumbPath(videoPath: string): string;
/**
 * Ensure a cached poster frame exists for `videoPath`, returning its path.
 *
 * Cache hit: returns the existing thumb path when it is present AND newer than
 * the source video (mtime compare) — so a re-rendered video re-extracts.
 * Otherwise shells out to ffmpeg to grab a single frame at t=1s, scaled to
 * 480px wide. Returns `undefined` on ANY failure (no ffmpeg, unreadable video,
 * timeout, empty output) — never throws.
 */
export declare function ensureLooseThumbnail(videoPath: string): Promise<string | undefined>;
/**
 * Warm the thumbnail cache for many videos with a bounded concurrency window
 * (CONCURRENCY at a time). Individual failures are ignored — a missing or
 * unreadable video simply has no cached thumb and falls back to the gradient
 * placeholder in the UI.
 */
export declare function ensureLooseThumbnails(videos: string[]): Promise<void>;
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