silence.js 1.7 KB

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  1. var highPrefix = [33, 16, 5, 32, 164, 27];
  2. var lowPrefix = [33, 65, 108, 84, 1, 2, 4, 8, 168, 2, 4, 8, 17, 191, 252];
  3. var zeroFill = function(count) {
  4. var a = [];
  5. while (count--) {
  6. a.push(0);
  7. }
  8. return a;
  9. };
  10. var makeTable = function(metaTable) {
  11. return Object.keys(metaTable).reduce(function(obj, key) {
  12. obj[key] = new Uint8Array(metaTable[key].reduce(function(arr, part) {
  13. return arr.concat(part);
  14. }, []));
  15. return obj;
  16. }, {});
  17. };
  18. // Frames-of-silence to use for filling in missing AAC frames
  19. var coneOfSilence = {
  20. 96000: [highPrefix, [227, 64], zeroFill(154), [56]],
  21. 88200: [highPrefix, [231], zeroFill(170), [56]],
  22. 64000: [highPrefix, [248, 192], zeroFill(240), [56]],
  23. 48000: [highPrefix, [255, 192], zeroFill(268), [55, 148, 128], zeroFill(54), [112]],
  24. 44100: [highPrefix, [255, 192], zeroFill(268), [55, 163, 128], zeroFill(84), [112]],
  25. 32000: [highPrefix, [255, 192], zeroFill(268), [55, 234], zeroFill(226), [112]],
  26. 24000: [highPrefix, [255, 192], zeroFill(268), [55, 255, 128], zeroFill(268), [111, 112], zeroFill(126), [224]],
  27. 16000: [highPrefix, [255, 192], zeroFill(268), [55, 255, 128], zeroFill(268), [111, 255], zeroFill(269), [223, 108], zeroFill(195), [1, 192]],
  28. 12000: [lowPrefix, zeroFill(268), [3, 127, 248], zeroFill(268), [6, 255, 240], zeroFill(268), [13, 255, 224], zeroFill(268), [27, 253, 128], zeroFill(259), [56]],
  29. 11025: [lowPrefix, zeroFill(268), [3, 127, 248], zeroFill(268), [6, 255, 240], zeroFill(268), [13, 255, 224], zeroFill(268), [27, 255, 192], zeroFill(268), [55, 175, 128], zeroFill(108), [112]],
  30. 8000: [lowPrefix, zeroFill(268), [3, 121, 16], zeroFill(47), [7]]
  31. };
  32. module.exports = makeTable(coneOfSilence);