/**
 * H.264 to JPEG frame decoder using a persistent ffmpeg subprocess.
 *
 * Spawns ffmpeg with H.264 stdin → MJPEG stdout, extracts individual
 * JPEG frames by scanning for SOI (FF D8) / EOI (FF D9) markers.
 */
import { EventEmitter } from "node:events";
/**
 * Extract complete JPEG frames from a buffer.
 * Returns extracted frames and the remaining unprocessed bytes.
 */
export declare function extractJpegFrames(buf: Buffer): {
    frames: Buffer[];
    remainder: Buffer;
};
export interface FrameDecoderEvents {
    frame: [jpeg: Buffer];
    error: [err: Error];
}
/**
 * Persistent ffmpeg-based H.264 → JPEG decoder.
 *
 * Usage:
 *   const decoder = new FrameDecoder();
 *   decoder.start();
 *   decoder.feed(nalData);
 *   const jpeg = decoder.getFrame();
 *   decoder.stop();
 */
export declare class FrameDecoder extends EventEmitter {
    private proc;
    private latestFrame;
    private readBuffer;
    private running;
    /** Check that ffmpeg is available on PATH. */
    static checkFfmpeg(): void;
    /** Start the persistent ffmpeg decoder process. */
    start(): void;
    /** Feed H.264 NAL data to the decoder. */
    feed(nalData: Buffer): void;
    /** Get the latest decoded JPEG frame, or null if none available. */
    getFrame(): Buffer | null;
    /** Stop the decoder and kill the ffmpeg process. */
    stop(): void;
    /** Whether the decoder is currently running. */
    get isRunning(): boolean;
}
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