Home Reference Source

src/remux/aac-helper.ts

  1. /**
  2.  *  AAC helper
  3.  */
  4.  
  5. class AAC {
  6.   static getSilentFrame(
  7.     codec?: string,
  8.     channelCount?: number
  9.   ): Uint8Array | undefined {
  10.     switch (codec) {
  11.       case 'mp4a.40.2':
  12.         if (channelCount === 1) {
  13.           return new Uint8Array([0x00, 0xc8, 0x00, 0x80, 0x23, 0x80]);
  14.         } else if (channelCount === 2) {
  15.           return new Uint8Array([
  16.             0x21, 0x00, 0x49, 0x90, 0x02, 0x19, 0x00, 0x23, 0x80,
  17.           ]);
  18.         } else if (channelCount === 3) {
  19.           return new Uint8Array([
  20.             0x00, 0xc8, 0x00, 0x80, 0x20, 0x84, 0x01, 0x26, 0x40, 0x08, 0x64,
  21.             0x00, 0x8e,
  22.           ]);
  23.         } else if (channelCount === 4) {
  24.           return new Uint8Array([
  25.             0x00, 0xc8, 0x00, 0x80, 0x20, 0x84, 0x01, 0x26, 0x40, 0x08, 0x64,
  26.             0x00, 0x80, 0x2c, 0x80, 0x08, 0x02, 0x38,
  27.           ]);
  28.         } else if (channelCount === 5) {
  29.           return new Uint8Array([
  30.             0x00, 0xc8, 0x00, 0x80, 0x20, 0x84, 0x01, 0x26, 0x40, 0x08, 0x64,
  31.             0x00, 0x82, 0x30, 0x04, 0x99, 0x00, 0x21, 0x90, 0x02, 0x38,
  32.           ]);
  33.         } else if (channelCount === 6) {
  34.           return new Uint8Array([
  35.             0x00, 0xc8, 0x00, 0x80, 0x20, 0x84, 0x01, 0x26, 0x40, 0x08, 0x64,
  36.             0x00, 0x82, 0x30, 0x04, 0x99, 0x00, 0x21, 0x90, 0x02, 0x00, 0xb2,
  37.             0x00, 0x20, 0x08, 0xe0,
  38.           ]);
  39.         }
  40.  
  41.         break;
  42.       // handle HE-AAC below (mp4a.40.5 / mp4a.40.29)
  43.       default:
  44.         if (channelCount === 1) {
  45.           // ffmpeg -y -f lavfi -i "aevalsrc=0:d=0.05" -c:a libfdk_aac -profile:a aac_he -b:a 4k output.aac && hexdump -v -e '16/1 "0x%x," "\n"' -v output.aac
  46.           return new Uint8Array([
  47.             0x1, 0x40, 0x22, 0x80, 0xa3, 0x4e, 0xe6, 0x80, 0xba, 0x8, 0x0, 0x0,
  48.             0x0, 0x1c, 0x6, 0xf1, 0xc1, 0xa, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  49.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  50.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  51.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  52.             0x5a, 0x5e,
  53.           ]);
  54.         } else if (channelCount === 2) {
  55.           // ffmpeg -y -f lavfi -i "aevalsrc=0|0:d=0.05" -c:a libfdk_aac -profile:a aac_he_v2 -b:a 4k output.aac && hexdump -v -e '16/1 "0x%x," "\n"' -v output.aac
  56.           return new Uint8Array([
  57.             0x1, 0x40, 0x22, 0x80, 0xa3, 0x5e, 0xe6, 0x80, 0xba, 0x8, 0x0, 0x0,
  58.             0x0, 0x0, 0x95, 0x0, 0x6, 0xf1, 0xa1, 0xa, 0x5a, 0x5a, 0x5a, 0x5a,
  59.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  60.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  61.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  62.             0x5a, 0x5e,
  63.           ]);
  64.         } else if (channelCount === 3) {
  65.           // ffmpeg -y -f lavfi -i "aevalsrc=0|0|0:d=0.05" -c:a libfdk_aac -profile:a aac_he_v2 -b:a 4k output.aac && hexdump -v -e '16/1 "0x%x," "\n"' -v output.aac
  66.           return new Uint8Array([
  67.             0x1, 0x40, 0x22, 0x80, 0xa3, 0x5e, 0xe6, 0x80, 0xba, 0x8, 0x0, 0x0,
  68.             0x0, 0x0, 0x95, 0x0, 0x6, 0xf1, 0xa1, 0xa, 0x5a, 0x5a, 0x5a, 0x5a,
  69.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  70.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  71.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  72.             0x5a, 0x5e,
  73.           ]);
  74.         }
  75.         break;
  76.     }
  77.     return undefined;
  78.   }
  79. }
  80.  
  81. export default AAC;