Source: lib/transmuxer/adts.js

  1. /*! @license
  2.  * Shaka Player
  3.  * Copyright 2016 Google LLC
  4.  * SPDX-License-Identifier: Apache-2.0
  5.  */
  7. // cspell:ignore lavfi aevalsrc libfdk hexdump
  9. goog.provide('shaka.transmuxer.ADTS');
  12. /**
  13.  * ADTS utils
  14.  */
  15. shaka.transmuxer.ADTS = class {
  16.   /**
  17.    * @param {!Uint8Array} data
  18.    * @param {!number} offset
  19.    * @return {?{headerLength: number, frameLength: number}}
  20.    */
  21.   static parseHeader(data, offset) {
  22.     const ADTS = shaka.transmuxer.ADTS;
  23.     // The protection skip bit tells us if we have 2 bytes of CRC data at the
  24.     // end of the ADTS header
  25.     const headerLength = ADTS.getHeaderLength(data, offset);
  26.     if (offset + headerLength <= data.length) {
  27.       // retrieve frame size
  28.       const frameLength = ADTS.getFullFrameLength(data, offset) - headerLength;
  29.       if (frameLength > 0) {
  30.         return {
  31.           headerLength,
  32.           frameLength,
  33.         };
  34.       }
  35.     }
  36.     return null;
  37.   }
  39.   /**
  40.    * @param {!Uint8Array} data
  41.    * @param {!number} offset
  42.    * @return {?{sampleRate: number, channelCount: number, codec: string}}
  43.    */
  44.   static parseInfo(data, offset) {
  45.     const adtsSamplingRates = [
  46.       96000,
  47.       88200,
  48.       64000,
  49.       48000,
  50.       44100,
  51.       32000,
  52.       24000,
  53.       22050,
  54.       16000,
  55.       12000,
  56.       11025,
  57.       8000,
  58.       7350,
  59.     ];
  60.     const adtsSamplingIndex = (data[offset + 2] & 0x3c) >>> 2;
  61.     if (adtsSamplingIndex > adtsSamplingRates.length - 1) {
  62.       return null;
  63.     }
  64.     const adtsObjectType = ((data[offset + 2] & 0xc0) >>> 6) + 1;
  65.     let adtsChannelConfig = (data[offset + 2] & 0x01) << 2;
  66.     adtsChannelConfig |= (data[offset + 3] & 0xc0) >>> 6;
  67.     return {
  68.       sampleRate: adtsSamplingRates[adtsSamplingIndex],
  69.       channelCount: adtsChannelConfig,
  70.       codec: 'mp4a.40.' + adtsObjectType,
  71.     };
  72.   }
  74.   /**
  75.    * @param {!Uint8Array} data
  76.    * @param {!number} offset
  77.    * @return {boolean}
  78.    */
  79.   static isHeaderPattern(data, offset) {
  80.     return data[offset] === 0xff && (data[offset + 1] & 0xf6) === 0xf0;
  81.   }
  83.   /**
  84.    * @param {!Uint8Array} data
  85.    * @param {!number} offset
  86.    * @return {number}
  87.    */
  88.   static getHeaderLength(data, offset) {
  89.     return data[offset + 1] & 0x01 ? 7 : 9;
  90.   }
  92.   /**
  93.    * @param {!Uint8Array} data
  94.    * @param {!number} offset
  95.    * @return {number}
  96.    */
  97.   static getFullFrameLength(data, offset) {
  98.     return ((data[offset + 3] & 0x03) << 11) |
  99.         (data[offset + 4] << 3) |
  100.         ((data[offset + 5] & 0xe0) >>> 5);
  101.   }
  103.   /**
  104.    * @param {!Uint8Array} data
  105.    * @param {!number} offset
  106.    * @return {boolean}
  107.    */
  108.   static isHeader(data, offset) {
  109.     const ADTS = shaka.transmuxer.ADTS;
  110.     // Look for ADTS header | 1111 1111 | 1111 X00X | where X can be
  111.     // either 0 or 1
  112.     // Layer bits (position 14 and 15) in header should be always 0 for ADTS
  113.     // More info https://wiki.multimedia.cx/index.php?title=ADTS
  114.     return offset + 1 < data.length && ADTS.isHeaderPattern(data, offset);
  115.   }
  117.   /**
  118.    * @param {!Uint8Array} data
  119.    * @param {!number} offset
  120.    * @return {boolean}
  121.    */
  122.   static probe(data, offset) {
  123.     const ADTS = shaka.transmuxer.ADTS;
  124.     // same as isHeader but we also check that ADTS frame follows last ADTS
  125.     // frame or end of data is reached
  126.     if (ADTS.isHeader(data, offset)) {
  127.       // ADTS header Length
  128.       const headerLength = ADTS.getHeaderLength(data, offset);
  129.       if (offset + headerLength >= data.length) {
  130.         return false;
  131.       }
  132.       // ADTS frame Length
  133.       const frameLength = ADTS.getFullFrameLength(data, offset);
  134.       if (frameLength <= headerLength) {
  135.         return false;
  136.       }
  138.       const newOffset = offset + frameLength;
  139.       return newOffset === data.length || ADTS.isHeader(data, newOffset);
  140.     }
  141.     return false;
  142.   }
  144.   /**
  145.    * @param {!number} samplerate
  146.    * @return {number}
  147.    */
  148.   static getFrameDuration(samplerate) {
  149.     return (shaka.transmuxer.ADTS.AAC_SAMPLES_PER_FRAME * 90000) / samplerate;
  150.   }
  152.   /**
  153.    * @param {string} codec
  154.    * @param {number} channelCount
  155.    * @return {?Uint8Array}
  156.    */
  157.   static getSilentFrame(codec, channelCount) {
  158.     switch (codec) {
  159.       case 'mp4a.40.2':
  160.         if (channelCount === 1) {
  161.           return new Uint8Array([0x00, 0xc8, 0x00, 0x80, 0x23, 0x80]);
  162.         } else if (channelCount === 2) {
  163.           return new Uint8Array([
  164.             0x21, 0x00, 0x49, 0x90, 0x02, 0x19, 0x00, 0x23, 0x80,
  165.           ]);
  166.         } else if (channelCount === 3) {
  167.           return new Uint8Array([
  168.             0x00, 0xc8, 0x00, 0x80, 0x20, 0x84, 0x01, 0x26, 0x40, 0x08, 0x64,
  169.             0x00, 0x8e,
  170.           ]);
  171.         } else if (channelCount === 4) {
  172.           return new Uint8Array([
  173.             0x00, 0xc8, 0x00, 0x80, 0x20, 0x84, 0x01, 0x26, 0x40, 0x08, 0x64,
  174.             0x00, 0x80, 0x2c, 0x80, 0x08, 0x02, 0x38,
  175.           ]);
  176.         } else if (channelCount === 5) {
  177.           return new Uint8Array([
  178.             0x00, 0xc8, 0x00, 0x80, 0x20, 0x84, 0x01, 0x26, 0x40, 0x08, 0x64,
  179.             0x00, 0x82, 0x30, 0x04, 0x99, 0x00, 0x21, 0x90, 0x02, 0x38,
  180.           ]);
  181.         } else if (channelCount === 6) {
  182.           return new Uint8Array([
  183.             0x00, 0xc8, 0x00, 0x80, 0x20, 0x84, 0x01, 0x26, 0x40, 0x08, 0x64,
  184.             0x00, 0x82, 0x30, 0x04, 0x99, 0x00, 0x21, 0x90, 0x02, 0x00, 0xb2,
  185.             0x00, 0x20, 0x08, 0xe0,
  186.           ]);
  187.         }
  188.         break;
  189.       // handle HE-AAC below (mp4a.40.5 / mp4a.40.29)
  190.       default:
  191.         if (channelCount === 1) {
  192.           // eslint-disable-next-line max-len
  193.           // 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
  194.           return new Uint8Array([
  195.             0x1, 0x40, 0x22, 0x80, 0xa3, 0x4e, 0xe6, 0x80, 0xba, 0x8, 0x0, 0x0,
  196.             0x0, 0x1c, 0x6, 0xf1, 0xc1, 0xa, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  197.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  198.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  199.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  200.             0x5a, 0x5e,
  201.           ]);
  202.         } else if (channelCount === 2) {
  203.           // eslint-disable-next-line max-len
  204.           // 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
  205.           return new Uint8Array([
  206.             0x1, 0x40, 0x22, 0x80, 0xa3, 0x5e, 0xe6, 0x80, 0xba, 0x8, 0x0, 0x0,
  207.             0x0, 0x0, 0x95, 0x0, 0x6, 0xf1, 0xa1, 0xa, 0x5a, 0x5a, 0x5a, 0x5a,
  208.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  209.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  210.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  211.             0x5a, 0x5e,
  212.           ]);
  213.         } else if (channelCount === 3) {
  214.           // eslint-disable-next-line max-len
  215.           // 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
  216.           return new Uint8Array([
  217.             0x1, 0x40, 0x22, 0x80, 0xa3, 0x5e, 0xe6, 0x80, 0xba, 0x8, 0x0, 0x0,
  218.             0x0, 0x0, 0x95, 0x0, 0x6, 0xf1, 0xa1, 0xa, 0x5a, 0x5a, 0x5a, 0x5a,
  219.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  220.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  221.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  222.             0x5a, 0x5e,
  223.           ]);
  224.         }
  225.         break;
  226.     }
  227.     return null;
  228.   }
  229. };
  231. /**
  232.  * @const {number}
  233.  */
  234. shaka.transmuxer.ADTS.AAC_SAMPLES_PER_FRAME = 1024;