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src/demux/mp3demuxer.ts

  1. /**
  2. * MP3 demuxer
  3. */
  4. import BaseAudioDemuxer from './base-audio-demuxer';
  5. import * as ID3 from '../demux/id3';
  6. import { logger } from '../utils/logger';
  7. import * as MpegAudio from './mpegaudio';
  8.  
  9. class MP3Demuxer extends BaseAudioDemuxer {
  10. resetInitSegment(
  11. initSegment: Uint8Array | undefined,
  12. audioCodec: string | undefined,
  13. videoCodec: string | undefined,
  14. trackDuration: number
  15. ) {
  16. super.resetInitSegment(initSegment, audioCodec, videoCodec, trackDuration);
  17. this._audioTrack = {
  18. container: 'audio/mpeg',
  19. type: 'audio',
  20. id: 2,
  21. pid: -1,
  22. sequenceNumber: 0,
  23. segmentCodec: 'mp3',
  24. samples: [],
  25. manifestCodec: audioCodec,
  26. duration: trackDuration,
  27. inputTimeScale: 90000,
  28. dropped: 0,
  29. };
  30. }
  31.  
  32. static probe(data): boolean {
  33. if (!data) {
  34. return false;
  35. }
  36.  
  37. // check if data contains ID3 timestamp and MPEG sync word
  38. // Look for MPEG header | 1111 1111 | 111X XYZX | where X can be either 0 or 1 and Y or Z should be 1
  39. // Layer bits (position 14 and 15) in header should be always different from 0 (Layer I or Layer II or Layer III)
  40. // More info http://www.mp3-tech.org/programmer/frame_header.html
  41. const id3Data = ID3.getID3Data(data, 0) || [];
  42. let offset = id3Data.length;
  43.  
  44. for (let length = data.length; offset < length; offset++) {
  45. if (MpegAudio.probe(data, offset)) {
  46. logger.log('MPEG Audio sync word found !');
  47. return true;
  48. }
  49. }
  50. return false;
  51. }
  52.  
  53. canParse(data, offset) {
  54. return MpegAudio.canParse(data, offset);
  55. }
  56.  
  57. appendFrame(track, data, offset) {
  58. if (this.basePTS === null) {
  59. return;
  60. }
  61. return MpegAudio.appendFrame(
  62. track,
  63. data,
  64. offset,
  65. this.basePTS,
  66. this.frameIndex
  67. );
  68. }
  69. }
  70.  
  71. export default MP3Demuxer;