import type { Host } from "../host/host.js";
export declare const TRANSCODE_FORMATS: readonly ["wav", "mp3", "m4a", "pcm"];
export type TranscodeFormat = (typeof TRANSCODE_FORMATS)[number];
/** Plenty for speech, and a fraction of the WAV size. */
export declare const BITRATE = "96k";
export declare const FFMPEG_TIMEOUT_MS: number;
export declare class FfmpegError extends Error {
    constructor(message: string);
}
/** Throws when ffmpeg is not on PATH. Called before any interrupt, so
 *  nobody approves a file that cannot be written. */
export declare function assertFfmpegAvailable(): void;
/** Arguments that read a WAV stream from stdin, change its speed when
 *  `speed` is not 1, and write `outputFile`. The output path is one this
 *  module chose, never the caller's. */
export declare function buildTranscodeArgs(format: TranscodeFormat, speed: number, outputFile: string): string[];
/** The bytes of `wav` at `speed`, encoded as `format`. ffmpeg writes a temp
 *  file, because the m4a container needs a seekable output. The file is
 *  read back through the host's files, which refuse a symlink, and it is
 *  removed whether or not encoding succeeds. */
export declare function transcode(host: Host, wav: Uint8Array, format: TranscodeFormat, speed: number, signal: AbortSignal): Promise<Uint8Array>;