/**
 * Get the duration of an audio file using ffprobe
 * @param filePath - Path to the audio file
 * @returns Duration in seconds
 */
export declare function getAudioDuration(filePath: string): Promise<number>;
/**
 * Get the duration of a video file using ffprobe
 * @param filePath - Path to the video file
 * @returns Duration in seconds
 */
export declare function getVideoDuration(filePath: string): Promise<number>;
/**
 * Extend a video naturally to match target duration using progressive techniques.
 * Uses slowdown, frame interpolation, and freeze frames based on extension ratio.
 *
 * @param videoPath - Path to the source video
 * @param targetDuration - Target duration in seconds
 * @param outputPath - Path for the extended video output
 * @returns Promise that resolves when extension is complete
 */
export declare function extendVideoNaturally(videoPath: string, targetDuration: number, outputPath: string): Promise<void>;
