Source: lib/transmuxer/adts.js

  1. /*! @license
  2.  * Shaka Player
  3.  * Copyright 2016 Google LLC
  4.  * SPDX-License-Identifier: Apache-2.0
  5.  */
  7. goog.provide('shaka.transmuxer.ADTS');
  10. /**
  11.  * ADTS utils
  12.  */
  13. shaka.transmuxer.ADTS = class {
  14.   /**
  15.    * @param {!Uint8Array} data
  16.    * @param {!number} offset
  17.    * @return {?{headerLength: number, frameLength: number}}
  18.    */
  19.   static parseHeader(data, offset) {
  20.     const ADTS = shaka.transmuxer.ADTS;
  21.     // The protection skip bit tells us if we have 2 bytes of CRC data at the
  22.     // end of the ADTS header
  23.     const headerLength = ADTS.getHeaderLength(data, offset);
  24.     if (offset + headerLength <= data.length) {
  25.       // retrieve frame size
  26.       const frameLength = ADTS.getFullFrameLength(data, offset) - headerLength;
  27.       if (frameLength > 0) {
  28.         return {
  29.           headerLength,
  30.           frameLength,
  31.         };
  32.       }
  33.     }
  34.     return null;
  35.   }
  37.   /**
  38.    * @param {!Uint8Array} data
  39.    * @param {!number} offset
  40.    * @return {?{sampleRate: number, channelCount: number, codec: string}}
  41.    */
  42.   static parseInfo(data, offset) {
  43.     const adtsSamplingRates = [
  44.       96000,
  45.       88200,
  46.       64000,
  47.       48000,
  48.       44100,
  49.       32000,
  50.       24000,
  51.       22050,
  52.       16000,
  53.       12000,
  54.       11025,
  55.       8000,
  56.       7350,
  57.     ];
  58.     const adtsSamplingIndex = (data[offset + 2] & 0x3c) >>> 2;
  59.     if (adtsSamplingIndex > adtsSamplingRates.length - 1) {
  60.       return null;
  61.     }
  62.     const adtsObjectType = ((data[offset + 2] & 0xc0) >>> 6) + 1;
  63.     let adtsChannelConfig = (data[offset + 2] & 0x01) << 2;
  64.     adtsChannelConfig |= (data[offset + 3] & 0xc0) >>> 6;
  65.     return {
  66.       sampleRate: adtsSamplingRates[adtsSamplingIndex],
  67.       channelCount: adtsChannelConfig,
  68.       codec: 'mp4a.40.' + adtsObjectType,
  69.     };
  70.   }
  72.   /**
  73.    * @param {!Uint8Array} data
  74.    * @param {!number} offset
  75.    * @return {boolean}
  76.    */
  77.   static isHeaderPattern(data, offset) {
  78.     return data[offset] === 0xff && (data[offset + 1] & 0xf6) === 0xf0;
  79.   }
  81.   /**
  82.    * @param {!Uint8Array} data
  83.    * @param {!number} offset
  84.    * @return {number}
  85.    */
  86.   static getHeaderLength(data, offset) {
  87.     return data[offset + 1] & 0x01 ? 7 : 9;
  88.   }
  90.   /**
  91.    * @param {!Uint8Array} data
  92.    * @param {!number} offset
  93.    * @return {number}
  94.    */
  95.   static getFullFrameLength(data, offset) {
  96.     return ((data[offset + 3] & 0x03) << 11) |
  97.         (data[offset + 4] << 3) |
  98.         ((data[offset + 5] & 0xe0) >>> 5);
  99.   }
  101.   /**
  102.    * @param {!Uint8Array} data
  103.    * @param {!number} offset
  104.    * @return {boolean}
  105.    */
  106.   static isHeader(data, offset) {
  107.     const ADTS = shaka.transmuxer.ADTS;
  108.     // Look for ADTS header | 1111 1111 | 1111 X00X | where X can be
  109.     // either 0 or 1
  110.     // Layer bits (position 14 and 15) in header should be always 0 for ADTS
  111.     // More info https://wiki.multimedia.cx/index.php?title=ADTS
  112.     return offset + 1 < data.length && ADTS.isHeaderPattern(data, offset);
  113.   }
  115.   /**
  116.    * @param {!Uint8Array} data
  117.    * @param {!number} offset
  118.    * @return {boolean}
  119.    */
  120.   static probe(data, offset) {
  121.     const ADTS = shaka.transmuxer.ADTS;
  122.     // same as isHeader but we also check that ADTS frame follows last ADTS
  123.     // frame or end of data is reached
  124.     if (ADTS.isHeader(data, offset)) {
  125.       // ADTS header Length
  126.       const headerLength = ADTS.getHeaderLength(data, offset);
  127.       if (offset + headerLength >= data.length) {
  128.         return false;
  129.       }
  130.       // ADTS frame Length
  131.       const frameLength = ADTS.getFullFrameLength(data, offset);
  132.       if (frameLength <= headerLength) {
  133.         return false;
  134.       }
  136.       const newOffset = offset + frameLength;
  137.       return newOffset === data.length || ADTS.isHeader(data, newOffset);
  138.     }
  139.     return false;
  140.   }
  142.   /**
  143.    * @param {!number} samplerate
  144.    * @return {number}
  145.    */
  146.   static getFrameDuration(samplerate) {
  147.     return (shaka.transmuxer.ADTS.AAC_SAMPLES_PER_FRAME * 90000) / samplerate;
  148.   }
  150.   /**
  151.    * @param {string} codec
  152.    * @param {number} channelCount
  153.    * @return {?Uint8Array}
  154.    */
  155.   static getSilentFrame(codec, channelCount) {
  156.     switch (codec) {
  157.       case 'mp4a.40.2':
  158.         if (channelCount === 1) {
  159.           return new Uint8Array([0x00, 0xc8, 0x00, 0x80, 0x23, 0x80]);
  160.         } else if (channelCount === 2) {
  161.           return new Uint8Array([
  162.             0x21, 0x00, 0x49, 0x90, 0x02, 0x19, 0x00, 0x23, 0x80,
  163.           ]);
  164.         } else if (channelCount === 3) {
  165.           return new Uint8Array([
  166.             0x00, 0xc8, 0x00, 0x80, 0x20, 0x84, 0x01, 0x26, 0x40, 0x08, 0x64,
  167.             0x00, 0x8e,
  168.           ]);
  169.         } else if (channelCount === 4) {
  170.           return new Uint8Array([
  171.             0x00, 0xc8, 0x00, 0x80, 0x20, 0x84, 0x01, 0x26, 0x40, 0x08, 0x64,
  172.             0x00, 0x80, 0x2c, 0x80, 0x08, 0x02, 0x38,
  173.           ]);
  174.         } else if (channelCount === 5) {
  175.           return new Uint8Array([
  176.             0x00, 0xc8, 0x00, 0x80, 0x20, 0x84, 0x01, 0x26, 0x40, 0x08, 0x64,
  177.             0x00, 0x82, 0x30, 0x04, 0x99, 0x00, 0x21, 0x90, 0x02, 0x38,
  178.           ]);
  179.         } else if (channelCount === 6) {
  180.           return new Uint8Array([
  181.             0x00, 0xc8, 0x00, 0x80, 0x20, 0x84, 0x01, 0x26, 0x40, 0x08, 0x64,
  182.             0x00, 0x82, 0x30, 0x04, 0x99, 0x00, 0x21, 0x90, 0x02, 0x00, 0xb2,
  183.             0x00, 0x20, 0x08, 0xe0,
  184.           ]);
  185.         }
  186.         break;
  187.       // handle HE-AAC below (mp4a.40.5 / mp4a.40.29)
  188.       default:
  189.         if (channelCount === 1) {
  190.           // eslint-disable-next-line max-len
  191.           // 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
  192.           return new Uint8Array([
  193.             0x1, 0x40, 0x22, 0x80, 0xa3, 0x4e, 0xe6, 0x80, 0xba, 0x8, 0x0, 0x0,
  194.             0x0, 0x1c, 0x6, 0xf1, 0xc1, 0xa, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  195.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  196.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  197.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  198.             0x5a, 0x5e,
  199.           ]);
  200.         } else if (channelCount === 2) {
  201.           // eslint-disable-next-line max-len
  202.           // 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
  203.           return new Uint8Array([
  204.             0x1, 0x40, 0x22, 0x80, 0xa3, 0x5e, 0xe6, 0x80, 0xba, 0x8, 0x0, 0x0,
  205.             0x0, 0x0, 0x95, 0x0, 0x6, 0xf1, 0xa1, 0xa, 0x5a, 0x5a, 0x5a, 0x5a,
  206.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  207.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  208.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  209.             0x5a, 0x5e,
  210.           ]);
  211.         } else if (channelCount === 3) {
  212.           // eslint-disable-next-line max-len
  213.           // 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
  214.           return new Uint8Array([
  215.             0x1, 0x40, 0x22, 0x80, 0xa3, 0x5e, 0xe6, 0x80, 0xba, 0x8, 0x0, 0x0,
  216.             0x0, 0x0, 0x95, 0x0, 0x6, 0xf1, 0xa1, 0xa, 0x5a, 0x5a, 0x5a, 0x5a,
  217.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  218.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  219.             0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a,
  220.             0x5a, 0x5e,
  221.           ]);
  222.         }
  223.         break;
  224.     }
  225.     return null;
  226.   }
  227. };
  229. /**
  230.  * @const {number}
  231.  */
  232. shaka.transmuxer.ADTS.AAC_SAMPLES_PER_FRAME = 1024;