Source: lib/text/srt_text_parser.js

  1. /*! @license
  2.  * Shaka Player
  3.  * Copyright 2016 Google LLC
  4.  * SPDX-License-Identifier: Apache-2.0
  5.  */
  7. goog.provide('shaka.text.SrtTextParser');
  9. goog.require('goog.asserts');
  10. goog.require('shaka.text.TextEngine');
  11. goog.require('shaka.text.VttTextParser');
  12. goog.require('shaka.util.BufferUtils');
  13. goog.require('shaka.util.StringUtils');
  16. /**
  17.  * @implements {shaka.extern.TextParser}
  18.  * @export
  19.  */
  20. shaka.text.SrtTextParser = class {
  21.   /** */
  22.   constructor() {
  23.     /**
  24.      * @type {!shaka.extern.TextParser}
  25.      * @private
  26.      */
  27.     this.parser_ = new shaka.text.VttTextParser();
  28.   }
  30.   /**
  31.    * @override
  32.    * @export
  33.    */
  34.   parseInit(data) {
  35.     goog.asserts.assert(false, 'SRT does not have init segments');
  36.   }
  38.   /**
  39.    * @override
  40.    * @export
  41.    */
  42.   setSequenceMode(sequenceMode) {
  43.     // Unused.
  44.   }
  46.   /**
  47.    * @override
  48.    * @export
  49.    */
  50.   parseMedia(data, time) {
  51.     const SrtTextParser = shaka.text.SrtTextParser;
  52.     const BufferUtils = shaka.util.BufferUtils;
  53.     const StringUtils = shaka.util.StringUtils;
  55.     // Get the input as a string.
  56.     const str = StringUtils.fromUTF8(data);
  58.     const vvtText = SrtTextParser.srt2webvtt(str);
  60.     const newData = BufferUtils.toUint8(StringUtils.toUTF8(vvtText));
  62.     return this.parser_.parseMedia(newData, time);
  63.   }
  65.   /**
  66.    * Convert a SRT format to WebVTT
  67.    *
  68.    * @param {string} data
  69.    * @return {string}
  70.    * @export
  71.    */
  72.   static srt2webvtt(data) {
  73.     const SrtTextParser = shaka.text.SrtTextParser;
  74.     let result = 'WEBVTT\n\n';
  76.     // Supports no cues
  77.     if (data == '') {
  78.       return result;
  79.     }
  81.     // remove dos newlines
  82.     let srt = data.replace(/\r+/g, '');
  83.     // trim white space start and end
  84.     srt = srt.trim();
  86.     // get cues
  87.     const cuelist = srt.split('\n\n');
  88.     for (const cue of cuelist) {
  89.       result += SrtTextParser.convertSrtCue_(cue);
  90.     }
  92.     return result;
  93.   }
  95.   /**
  96.    * Convert a SRT cue into WebVTT cue
  97.    *
  98.    * @param {string} caption
  99.    * @return {string}
  100.    * @private
  101.    */
  102.   static convertSrtCue_(caption) {
  103.     const lines = caption.split(/\n/);
  105.     // detect and skip numeric identifier
  106.     if (lines[0].match(/\d+/)) {
  107.       lines.shift();
  108.     }
  110.     // convert time codes
  111.     lines[0] = lines[0].replace(/,/g, '.');
  113.     return lines.join('\n') + '\n\n';
  114.   }
  115. };
  118. shaka.text.TextEngine.registerParser(
  119.     'text/srt', () => new shaka.text.SrtTextParser());