/**
 * Activity C of the distributed render pipeline.
 *
 * `assemble(planDir, chunkPaths, audioPath, outputPath)` stitches per-chunk
 * outputs into the final deliverable. For mp4 / mov / webm this is
 * `ffmpeg -f concat -c copy` (free of re-encode loss because every
 * chunk's first frame is an IDR keyframe — the chunk encoder sets
 * `lockGopForChunkConcat` to enforce this, which for libvpx-vp9 also
 * disables alt-ref frames so concat seams remain independently
 * decodable). For png-sequence chunks (each chunk is a directory of
 * frames) this is a straight directory merge with global re-numbering.
 *
 * Mux + faststart for mp4 / mov / webm go through the engine's
 * `muxVideoWithAudio` + `applyFaststart` helpers — same path the
 * in-process renderer uses; we just feed concat output rather than
 * streaming-encoder output. (Faststart is a no-op for webm and mov —
 * applyFaststart copies the input verbatim.) Audio length is
 * pad-or-trimmed to `frameCount / fps` via
 * `padOrTrimAudioToVideoFrameCount` so the mux step doesn't introduce
 * sub-millisecond drift at the end of long renders.
 *
 * Pure function over local paths. No networking. The caller is responsible
 * for moving `outputPath` to its orchestration-level storage.
 */
import { type ProducerLogger } from "../../logger.js";
/**
 * Result of {@link assemble}. `fileSize` reflects the final file on disk
 * (mp4/mov) or the cumulative byte total of the frame directory
 * (png-sequence).
 */
export interface AssembleResult {
    outputPath: string;
    durationMs: number;
    framesEncoded: number;
    fileSize: number;
}
/**
 * Assemble the chunk outputs into a single deliverable.
 *
 * @param planDir — absolute path to the planDir produced by `plan()`.
 * @param chunkPaths — ordered chunk outputs, length === `chunks.json` length.
 *   For mp4/mov each entry is a path to an encoded chunk file; for
 *   png-sequence each entry is a path to a directory of frames.
 * @param audioPath — `<planDir>/audio.aac` for mux'd formats. Pass `null`
 *   when the composition has no audio (or `assemble` is being called for a
 *   format whose audio is muxed elsewhere). `assemble` always normalizes
 *   audio length against the assembled video's frame count when
 *   `audioPath` is non-null.
 * @param outputPath — final on-disk output (file for mp4/mov; directory
 *   for png-sequence — created if missing).
 */
export declare function assemble(planDir: string, chunkPaths: readonly string[], audioPath: string | null, outputPath: string, options?: {
    logger?: ProducerLogger;
    abortSignal?: AbortSignal;
    /**
     * Opt-in exact-CFR re-encode. When `true`, the assembled video is
     * re-encoded once at the end of the concat/single-chunk step with
     * `-fps_mode cfr -r <fps>` so the stream-level `avg_frame_rate`
     * matches the container's `r_frame_rate` exactly (and the file's
     * duration lands on the requested `frameCount / fps` to ms
     * precision, with no PTS-derived drift). Trade-off: ~2-5x the
     * stitch time for a 60s 1080p clip plus second-generation H.264
     * quality loss (negligible at `-crf 18` but non-zero). Default
     * `false` preserves the existing `-c copy` behavior. mp4 only
     * (libx264); webm / mov pass through unchanged because their
     * stream-copy paths don't exhibit the same avg-frame-rate drift.
     */
    cfr?: boolean;
}): Promise<AssembleResult>;
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