import { XmlMessage, pipelines, utils } from 'media-stream-library';
/**
 * Metadata handlers
 *
 * For video streams that also include ONVIF metadata,
 * once can specify a parser + synced callback to be run
 * whenever metadata occurs on the stream.
 *
 * The `parser` provided produces a scheduled message, that
 * will be returned later through the `cb` synched callback,
 * whenever the message is synchronized with the presentation.
 */
export interface MetadataXMLMessage extends XmlMessage {
    readonly xmlDocument: XMLDocument;
}
export interface ScheduledMessage {
    readonly ntpTimestamp: number | undefined;
    readonly data: unknown;
}
export declare type MetadataParser = (msg: MetadataXMLMessage) => ScheduledMessage;
export declare type MetadataCallback = (msg: ScheduledMessage) => void;
export interface MetadataHandler {
    /**
     * A parser that will receive an XML message and should return
     * a new message with at least an ntpTimestamp.
     */
    readonly parser: MetadataParser;
    /**
     * A synchronized callback that will be called whenever the message
     * produced by the parser is in sync with the video.
     */
    readonly cb: MetadataCallback;
}
/**
 * Attach ONVIF metadata handlers to a pipeline
 *
 * @param pipeline The (HTML5 video) pipeline to modify
 * @param handlers The handlers to deal with XML data
 */
export declare const attachMetadataHandler: (pipeline: pipelines.Html5VideoPipeline, { parser, cb }: MetadataHandler) => utils.Scheduler<ScheduledMessage>;