Source: lib/text/lrc_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.LrcTextParser');
  9. goog.require('goog.asserts');
  10. goog.require('shaka.log');
  11. goog.require('shaka.text.Cue');
  12. goog.require('shaka.text.TextEngine');
  13. goog.require('shaka.util.StringUtils');
  16. /**
  17.  * LRC file format: https://en.wikipedia.org/wiki/LRC_(file_format)
  18.  *
  19.  * @implements {shaka.extern.TextParser}
  20.  * @export
  21.  */
  22. shaka.text.LrcTextParser = class {
  23.   /**
  24.    * @override
  25.    * @export
  26.    */
  27.   parseInit(data) {
  28.     goog.asserts.assert(false, 'LRC does not have init segments');
  29.   }
  31.   /**
  32.    * @override
  33.    * @export
  34.    */
  35.   parseMedia(data, time) {
  36.     const StringUtils = shaka.util.StringUtils;
  37.     const LrcTextParser = shaka.text.LrcTextParser;
  39.     // Get the input as a string.
  40.     const str = StringUtils.fromUTF8(data);
  42.     /** @type {shaka.extern.Cue} */
  43.     let prevCue = null;
  45.     /** @type {!Array.<!shaka.extern.Cue>} */
  46.     const cues = [];
  47.     const lines = str.split(/\r?\n/);
  48.     for (const line of lines) {
  49.       if (!line || /^\s+$/.test(line)) {
  50.         continue;
  51.       }
  53.       // LRC content
  54.       const match = LrcTextParser.lyricLine_.exec(line);
  55.       if (match) {
  56.         const startTime = LrcTextParser.parseTime_(match[1]);
  57.         // This time can be overwritten by a subsequent cue.
  58.         // By default we add 2 seconds of duration.
  59.         const endTime = time.segmentEnd ? time.segmentEnd : startTime + 2;
  60.         const payload = match[2];
  61.         const cue = new shaka.text.Cue(startTime, endTime, payload);
  63.         // Update previous
  64.         if (prevCue) {
  65.           prevCue.endTime = startTime;
  66.           cues.push(prevCue);
  67.         }
  68.         prevCue = cue;
  69.         continue;
  70.       }
  71.       shaka.log.warning('LrcTextParser encountered an unknown line.', line);
  72.     }
  73.     if (prevCue) {
  74.       cues.push(prevCue);
  75.     }
  77.     return cues;
  78.   }
  80.   /**
  81.    * Parses a LRC time from the given parser.
  82.    *
  83.    * @param {string} string
  84.    * @return {number}
  85.    * @private
  86.    */
  87.   static parseTime_(string) {
  88.     const LrcTextParser = shaka.text.LrcTextParser;
  89.     const match = LrcTextParser.timeFormat_.exec(string);
  90.     const minutes = parseInt(match[1], 10);
  91.     const seconds = parseFloat(match[2].replace(',', '.'));
  92.     return minutes * 60 + seconds;
  93.   }
  94. };
  96. /**
  97.  * @const
  98.  * @private {!RegExp}
  99.  * @example [00:12.0]Text or [00:12.00]Text or [00:12.000]Text or
  100.  * [00:12,0]Text or [00:12,00]Text or [00:12,000]Text
  101.  */
  102. shaka.text.LrcTextParser.lyricLine_ =
  103.     /^\[(\d{1,2}:\d{1,2}(?:[.,]\d{1,3})?)\](.*)/;
  105. /**
  106.  * @const
  107.  * @private {!RegExp}
  108.  * @example 00:12.0 or 00:12.00 or 00:12.000 or
  109.  * 00:12,0 or 00:12,00 or 00:12,000
  110.  */
  111. shaka.text.LrcTextParser.timeFormat_ =
  112.     /^(\d+):(\d{1,2}(?:[.,]\d{1,3})?)$/;
  114. shaka.text.TextEngine.registerParser(
  115.     'application/x-subtitle-lrc', () => new shaka.text.LrcTextParser());