/**
 * How long a piece of audio or video is, read from the file's own headers, without decoding it and
 * without a dependency: WAV, MP4 and MOV, WebM and Matroska, MP3, Ogg (Vorbis and Opus), and FLAC.
 * Portable: plain bytes in, a number out.
 */
/** What the headers say: the length, the container's type, and whether it holds a picture. */
export interface MediaDuration {
    /** Its length in milliseconds. */
    durationMs: number;
    /** Its container's MIME type, such as `video/mp4` or `audio/ogg`. */
    mimeType: string;
    /** `video` when it holds a picture track, `audio` when only sound. */
    kind: 'audio' | 'video';
}
/**
 * The length of audio or video from its headers, or `undefined` when the bytes are none of the
 * containers read, or say no length: a stream still being written, or a file cut short before the
 * part that says it.
 */
export declare function readMediaDuration(bytes: Uint8Array): MediaDuration | undefined;