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123 lines
3.3 KiB
JavaScript
123 lines
3.3 KiB
JavaScript
const Writable = require('stream').Writable;
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const sax = require('sax');
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/**
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* A wrapper around sax that emits segments.
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*
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* @extends WRitableStream
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* @constructor
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*/
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module.exports = class DashMPDParser extends Writable {
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constructor(targetID) {
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super();
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this._parser = sax.createStream(false, { lowercasetags: true });
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this._parser.on('error', this.emit.bind(this, 'error'));
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let lastTag;
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let starttime = 0;
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let seq = 0;
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let timescale, offset, duration, baseURL;
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let timeline = [];
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let getSegments = false, startEmitted = false;
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let isStatic;
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let treeLevel;
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this._parser.on('opentag', (node) => {
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switch (node.name) {
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case 'mpd':
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starttime =
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new Date(node.attributes.availabilitystarttime).getTime();
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isStatic = node.attributes.type !== 'dynamic';
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break;
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case 'period':
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// Reset everything on <Period> tag.
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seq = 0;
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timescale = 1000;
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duration = 0;
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offset = 0;
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baseURL = [];
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treeLevel = 0;
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break;
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case 'segmentlist':
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seq = parseInt(node.attributes.startnumber, 10) || seq;
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timescale = parseInt(node.attributes.timescale, 10) || timescale;
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duration = parseInt(node.attributes.duration, 10) || duration;
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offset = parseInt(node.attributes.presentationtimeoffset, 10) || offset;
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if (!startEmitted) {
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startEmitted = true;
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if (offset) {
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starttime += offset;
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}
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this.emit('starttime', starttime);
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}
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break;
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case 'segmenttimeline':
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case 'baseurl':
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lastTag = node.name;
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break;
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case 's':
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timeline.push(parseInt(node.attributes.d, 10));
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break;
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case 'adaptationset':
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case 'representation':
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treeLevel++;
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if (targetID == null) {
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targetID = node.attributes.id;
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}
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getSegments = node.attributes.id === targetID + '';
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break;
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case 'segmenturl':
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if (getSegments) {
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let tl = timeline.shift();
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let segmentDuration = (tl || duration) / timescale * 1000;
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this.emit('item', {
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url: baseURL.filter(s => !!s).join('') + node.attributes.media,
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seq: seq++,
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duration: segmentDuration,
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});
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}
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break;
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}
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});
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const onEnd = () => {
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if (isStatic) { this.emit('endlist'); }
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if (!getSegments) {
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this.emit('error', new Error(`Representation '${targetID}' not found`));
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}
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this.emit('end');
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};
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this._parser.on('closetag', (tagName) => {
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switch (tagName) {
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case 'adaptationset':
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case 'representation':
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treeLevel--;
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break;
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case 'segmentlist':
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if (getSegments) {
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this.emit('endearly');
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onEnd();
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this._parser.removeAllListeners();
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}
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break;
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}
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});
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this._parser.on('text', (text) => {
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if (lastTag === 'baseurl') {
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baseURL[treeLevel] = text;
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lastTag = null;
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}
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});
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this.on('finish', onEnd);
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}
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_write(chunk, encoding, callback) {
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this._parser.write(chunk, encoding);
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callback();
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}
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};
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