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.   setSequenceMode(sequenceMode) {
  36.     // Unused.
  37.   }
  39.   /**
  40.    * @override
  41.    * @export
  42.    */
  43.   parseMedia(data, time) {
  44.     const StringUtils = shaka.util.StringUtils;
  45.     const LrcTextParser = shaka.text.LrcTextParser;
  47.     // Get the input as a string.
  48.     const str = StringUtils.fromUTF8(data);
  50.     /** @type {shaka.extern.Cue} */
  51.     let prevCue = null;
  53.     /** @type {!Array.<!shaka.extern.Cue>} */
  54.     const cues = [];
  55.     const lines = str.split(/\r?\n/);
  56.     for (const line of lines) {
  57.       if (!line || /^\s+$/.test(line)) {
  58.         continue;
  59.       }
  61.       // LRC content
  62.       const match = LrcTextParser.lyricLine_.exec(line);
  63.       if (match) {
  64.         const startTime = LrcTextParser.parseTime_(match[1]);
  65.         // This time can be overwritten by a subsequent cue.
  66.         // By default we add 2 seconds of duration.
  67.         const endTime = time.segmentEnd ? time.segmentEnd : startTime + 2;
  68.         const payload = match[2];
  69.         const cue = new shaka.text.Cue(startTime, endTime, payload);
  71.         // Update previous
  72.         if (prevCue) {
  73.           prevCue.endTime = startTime;
  74.           cues.push(prevCue);
  75.         }
  76.         prevCue = cue;
  77.         continue;
  78.       }
  79.       shaka.log.warning('LrcTextParser encountered an unknown line.', line);
  80.     }
  81.     if (prevCue) {
  82.       cues.push(prevCue);
  83.     }
  85.     return cues;
  86.   }
  88.   /**
  89.    * Parses a LRC time from the given parser.
  90.    *
  91.    * @param {string} string
  92.    * @return {number}
  93.    * @private
  94.    */
  95.   static parseTime_(string) {
  96.     const LrcTextParser = shaka.text.LrcTextParser;
  97.     const match = LrcTextParser.timeFormat_.exec(string);
  98.     const minutes = parseInt(match[1], 10);
  99.     const seconds = parseFloat(match[2].replace(',', '.'));
  100.     return minutes * 60 + seconds;
  101.   }
  102. };
  104. /**
  105.  * @const
  106.  * @private {!RegExp}
  107.  * @example [00:12.0]Text or [00:12.00]Text or [00:12.000]Text or
  108.  * [00:12,0]Text or [00:12,00]Text or [00:12,000]Text
  109.  */
  110. shaka.text.LrcTextParser.lyricLine_ =
  111.     /^\[(\d{1,2}:\d{1,2}(?:[.,]\d{1,3})?)\](.*)/;
  113. /**
  114.  * @const
  115.  * @private {!RegExp}
  116.  * @example 00:12.0 or 00:12.00 or 00:12.000 or
  117.  * 00:12,0 or 00:12,00 or 00:12,000
  118.  */
  119. shaka.text.LrcTextParser.timeFormat_ =
  120.     /^(\d+):(\d{1,2}(?:[.,]\d{1,3})?)$/;
  122. shaka.text.TextEngine.registerParser(
  123.     'application/x-subtitle-lrc', () => new shaka.text.LrcTextParser());