mp4-tools.ts

import { ElementaryStreamTypes } from '../loader/fragment';
import { sliceUint8 } from './typed-array';
import { utf8ArrayToStr } from '../demux/id3';
import { logger } from '../utils/logger';
import Hex from './hex';
import type { PassthroughTrack, UserdataSample } from '../types/demuxer';
import type { DecryptData } from '../loader/level-key';

const UINT32_MAX = Math.pow(2, 32) - 1;
const push = [].push;

// We are using fixed track IDs for driving the MP4 remuxer
// instead of following the TS PIDs.
// There is no reason not to do this and some browsers/SourceBuffer-demuxers
// may not like if there are TrackID "switches"
// See https://github.com/video-dev/hls.js/issues/1331
// Here we are mapping our internal track types to constant MP4 track IDs
// With MSE currently one can only have one track of each, and we are muxing
// whatever video/audio rendition in them.
export const RemuxerTrackIdConfig = {
  video: 1,
  audio: 2,
  id3: 3,
  text: 4,
};

export function bin2str(data: Uint8Array): string {
  return String.fromCharCode.apply(null, data);
}

export function readUint16(buffer: Uint8Array, offset: number): number {
  const val = (buffer[offset] << 8) | buffer[offset + 1];
  return val < 0 ? 65536 + val : val;
}

export function readUint32(buffer: Uint8Array, offset: number): number {
  const val = readSint32(buffer, offset);
  return val < 0 ? 4294967296 + val : val;
}

export function readSint32(buffer: Uint8Array, offset: number): number {
  return (
    (buffer[offset] << 24) |
    (buffer[offset + 1] << 16) |
    (buffer[offset + 2] << 8) |
    buffer[offset + 3]
  );
}

export function writeUint32(buffer: Uint8Array, offset: number, value: number) {
  buffer[offset] = value >> 24;
  buffer[offset + 1] = (value >> 16) & 0xff;
  buffer[offset + 2] = (value >> 8) & 0xff;
  buffer[offset + 3] = value & 0xff;
}

// Find the data for a box specified by its path
export function findBox(data: Uint8Array, path: string[]): Uint8Array[] {
  const results = [] as Uint8Array[];
  if (!path.length) {
    // short-circuit the search for empty paths
    return results;
  }
  const end = data.byteLength;

  for (let i = 0; i < end; ) {
    const size = readUint32(data, i);
    const type = bin2str(data.subarray(i + 4, i + 8));
    const endbox = size > 1 ? i + size : end;
    if (type === path[0]) {
      if (path.length === 1) {
        // this is the end of the path and we've found the box we were
        // looking for
        results.push(data.subarray(i + 8, endbox));
      } else {
        // recursively search for the next box along the path
        const subresults = findBox(data.subarray(i + 8, endbox), path.slice(1));
        if (subresults.length) {
          push.apply(results, subresults);
        }
      }
    }
    i = endbox;
  }

  // we've finished searching all of data
  return results;
}

type SidxInfo = {
  earliestPresentationTime: number;
  timescale: number;
  version: number;
  referencesCount: number;
  references: any[];
};

export function parseSegmentIndex(sidx: Uint8Array): SidxInfo | null {
  const references: any[] = [];

  const version = sidx[0];

  // set initial offset, we skip the reference ID (not needed)
  let index = 8;

  const timescale = readUint32(sidx, index);
  index += 4;

  // TODO: parse earliestPresentationTime and firstOffset
  // usually zero in our case
  const earliestPresentationTime = 0;
  const firstOffset = 0;

  if (version === 0) {
    index += 8;
  } else {
    index += 16;
  }

  // skip reserved
  index += 2;

  let startByte = sidx.length + firstOffset;

  const referencesCount = readUint16(sidx, index);
  index += 2;

  for (let i = 0; i < referencesCount; i++) {
    let referenceIndex = index;

    const referenceInfo = readUint32(sidx, referenceIndex);
    referenceIndex += 4;

    const referenceSize = referenceInfo & 0x7fffffff;
    const referenceType = (referenceInfo & 0x80000000) >>> 31;

    if (referenceType === 1) {
      logger.warn('SIDX has hierarchical references (not supported)');
      return null;
    }

    const subsegmentDuration = readUint32(sidx, referenceIndex);
    referenceIndex += 4;

    references.push({
      referenceSize,
      subsegmentDuration, // unscaled
      info: {
        duration: subsegmentDuration / timescale,
        start: startByte,
        end: startByte + referenceSize - 1,
      },
    });

    startByte += referenceSize;

    // Skipping 1 bit for |startsWithSap|, 3 bits for |sapType|, and 28 bits
    // for |sapDelta|.
    referenceIndex += 4;

    // skip to next ref
    index = referenceIndex;
  }

  return {
    earliestPresentationTime,
    timescale,
    version,
    referencesCount,
    references,
  };
}

/**
 * Parses an MP4 initialization segment and extracts stream type and
 * timescale values for any declared tracks. Timescale values indicate the
 * number of clock ticks per second to assume for time-based values
 * elsewhere in the MP4.
 *
 * To determine the start time of an MP4, you need two pieces of
 * information: the timescale unit and the earliest base media decode
 * time. Multiple timescales can be specified within an MP4 but the
 * base media decode time is always expressed in the timescale from
 * the media header box for the track:
 * ```
 * moov > trak > mdia > mdhd.timescale
 * moov > trak > mdia > hdlr
 * ```
 * @param initSegment the bytes of the init segment
 * @returns a hash of track type to timescale values or null if
 * the init segment is malformed.
 */

export interface InitDataTrack {
  timescale: number;
  id: number;
  codec: string;
}

type HdlrType = ElementaryStreamTypes.AUDIO | ElementaryStreamTypes.VIDEO;

export interface InitData extends Array<any> {
  [index: number]:
    | {
        timescale: number;
        type: HdlrType;
        default?: {
          duration: number;
          flags: number;
        };
      }
    | undefined;
  audio?: InitDataTrack;
  video?: InitDataTrack;
  caption?: InitDataTrack;
}

export function parseInitSegment(initSegment: Uint8Array): InitData {
  const result: InitData = [];
  const traks = findBox(initSegment, ['moov', 'trak']);
  for (let i = 0; i < traks.length; i++) {
    const trak = traks[i];
    const tkhd = findBox(trak, ['tkhd'])[0];
    if (tkhd) {
      let version = tkhd[0];
      let index = version === 0 ? 12 : 20;
      const trackId = readUint32(tkhd, index);
      const mdhd = findBox(trak, ['mdia', 'mdhd'])[0];
      if (mdhd) {
        version = mdhd[0];
        index = version === 0 ? 12 : 20;
        const timescale = readUint32(mdhd, index);
        const hdlr = findBox(trak, ['mdia', 'hdlr'])[0];
        if (hdlr) {
          const hdlrType = bin2str(hdlr.subarray(8, 12));
          const type: HdlrType | undefined = {
            soun: ElementaryStreamTypes.AUDIO as const,
            vide: ElementaryStreamTypes.VIDEO as const,
          }[hdlrType];
          if (type) {
            // Parse codec details
            const stsd = findBox(trak, ['mdia', 'minf', 'stbl', 'stsd'])[0];
            let codec;
            if (stsd) {
              codec = bin2str(stsd.subarray(12, 16));
              // Parse codec details to be able to build MIME type
              // TODO: Codec parsing support for AV1
              const toHex = (x: number): string => {
                return ('0' + x.toString(16).toUpperCase()).slice(-2);
              };

              // Handle H264
              if (
                codec.slice(0, 3) === 'avc' &&
                codec[3] >= '1' &&
                codec[3] <= '4' &&
                stsd.length > 102 &&
                bin2str(stsd.subarray(98, 102)) === 'avcC'
              ) {
                // profile + compatibility + level
                codec +=
                  '.' + toHex(stsd[111]) + toHex(stsd[112]) + toHex(stsd[113]);
              }

              // Handle H265
              else if (isHEVC(codec)) {
                // @fogarasyroland's method https://github.com/video-dev/hls.js/pull/5024
                let hvcC;
                const codecBox = findBox(stsd.subarray(8), [codec])[0];
                if (codecBox) {
                  const { end } = parseVisualSampleEntry(codecBox);
                  hvcC = findBox(codecBox.subarray(end), ['hvcC'])[0];
                  if (hvcC) {
                    codec = mimeTypeBuilderHEVC(
                      codec,
                      parseHvcConfigurationRecord(hvcC)
                    );
                  }
                }
                // @uvjustin's method https://github.com/video-dev/hls.js/pull/4996
                if (
                  !hvcC &&
                  stsd.length > 102 &&
                  bin2str(stsd.subarray(98, 102)) === 'hvcC'
                ) {
                  // Profile Space
                  const profileByte = stsd[103];
                  const profileSpace = { 0: '', 1: 'A', 2: 'B', 3: 'C' }[
                    profileByte >> 6
                  ];
                  const generalProfileIdc = profileByte & 31;
                  codec += '.' + profileSpace + generalProfileIdc;

                  // Compatibility
                  let reversed = 0;
                  for (let i = 0; i < 4; ++i) {
                    // byte number
                    for (let j = 0; j < 8; ++j) {
                      // bit number
                      reversed |=
                        ((stsd[i + 104] >> (7 - j)) & 1) << (31 - 8 * i - j);
                    }
                  }
                  codec += '.' + toHex(reversed >>> 0);

                  // Tier Flag
                  codec += (profileByte & 32 ? '.H' : '.L') + stsd[114];

                  // Constraint String
                  let hasByte = false;
                  let constraintString = '';
                  for (let i = 113; i > 107; --i) {
                    if (stsd[i] || hasByte) {
                      constraintString =
                        '.' + toHex(stsd[i]) + constraintString;
                      hasByte = true;
                    }
                  }
                  codec += constraintString;
                }
              }

              // Handle Audio
              else if (codec === 'mp4a') {
                // Parse ES Descriptors
                let i: number;
                // oti
                for (i = 0; i < stsd.length - 5; ++i) {
                  if (
                    stsd[i] == 4 &&
                    stsd[i + 1] == 128 &&
                    stsd[i + 2] == 128 &&
                    stsd[i + 3] == 128
                  ) {
                    codec += '.' + toHex(stsd[i + 5]);
                    break;
                  }
                }

                // dsi
                for (i = 0; i < stsd.length - 6; ++i) {
                  if (
                    stsd[i] == 5 &&
                    stsd[i + 1] == 128 &&
                    stsd[i + 2] == 128 &&
                    stsd[i + 3] == 128
                  ) {
                    let dsi = (stsd[i + 5] & 248) >> 3;
                    if (dsi == 31 && stsd[i + 4] >= 2) {
                      dsi =
                        32 +
                        ((stsd[i + 5] & 7) << 3) +
                        ((stsd[i + 6] & 224) >> 5);
                    }
                    codec += '.' + dsi;
                    break;
                  }
                }
              }
            }
            result[trackId] = { timescale, type };
            result[type] = { timescale, id: trackId, codec };
          }
        }
      }
    }
  }

  const trex = findBox(initSegment, ['moov', 'mvex', 'trex']);
  trex.forEach((trex) => {
    const trackId = readUint32(trex, 4);
    const track = result[trackId];
    if (track) {
      track.default = {
        duration: readUint32(trex, 12),
        flags: readUint32(trex, 20),
      };
    }
  });

  return result;
}

export function patchEncyptionData(
  initSegment: Uint8Array | undefined,
  decryptdata: DecryptData | null
): Uint8Array | undefined {
  if (!initSegment || !decryptdata) {
    return initSegment;
  }
  const keyId = decryptdata.keyId;
  if (keyId && decryptdata.isCommonEncryption) {
    const traks = findBox(initSegment, ['moov', 'trak']);
    traks.forEach((trak) => {
      const stsd = findBox(trak, ['mdia', 'minf', 'stbl', 'stsd'])[0];

      // skip the sample entry count
      const sampleEntries = stsd.subarray(8);
      let encBoxes = findBox(sampleEntries, ['enca']);
      const isAudio = encBoxes.length > 0;
      if (!isAudio) {
        encBoxes = findBox(sampleEntries, ['encv']);
      }
      encBoxes.forEach((enc) => {
        const encBoxChildren = isAudio ? enc.subarray(28) : enc.subarray(78);
        const sinfBoxes = findBox(encBoxChildren, ['sinf']);
        sinfBoxes.forEach((sinf) => {
          const tenc = parseSinf(sinf);
          if (tenc) {
            // Look for default key id (keyID offset is always 8 within the tenc box):
            const tencKeyId = tenc.subarray(8, 24);
            if (!tencKeyId.some((b) => b !== 0)) {
              logger.log(
                `[eme] Patching keyId in 'enc${
                  isAudio ? 'a' : 'v'
                }>sinf>>tenc' box: ${Hex.hexDump(tencKeyId)} -> ${Hex.hexDump(
                  keyId
                )}`
              );
              tenc.set(keyId, 8);
            }
          }
        });
      });
    });
  }

  return initSegment;
}

export function parseSinf(sinf: Uint8Array): Uint8Array | null {
  const schm = findBox(sinf, ['schm'])[0];
  if (schm) {
    const scheme = bin2str(schm.subarray(4, 8));
    if (scheme === 'cbcs' || scheme === 'cenc') {
      return findBox(sinf, ['schi', 'tenc'])[0];
    }
  }
  logger.error(`[eme] missing 'schm' box`);
  return null;
}

/**
 * Determine the base media decode start time, in seconds, for an MP4
 * fragment. If multiple fragments are specified, the earliest time is
 * returned.
 *
 * The base media decode time can be parsed from track fragment
 * metadata:
 * ```
 * moof > traf > tfdt.baseMediaDecodeTime
 * ```
 * It requires the timescale value from the mdhd to interpret.
 *
 * @param initData - a hash of track type to timescale values
 * @param fmp4 - the bytes of the mp4 fragment
 * @returns the earliest base media decode start time for the
 * fragment, in seconds
 */
export function getStartDTS(
  initData: InitData,
  fmp4: Uint8Array
): number | null {
  // we need info from two children of each track fragment box
  return findBox(fmp4, ['moof', 'traf']).reduce(
    (result: number | null, traf) => {
      const tfdt = findBox(traf, ['tfdt'])[0];
      const version = tfdt[0];
      const start = findBox(traf, ['tfhd']).reduce(
        (result: number | null, tfhd) => {
          // get the track id from the tfhd
          const id = readUint32(tfhd, 4);
          const track = initData[id];
          if (track) {
            let baseTime = readUint32(tfdt, 4);
            if (version === 1) {
              // If value is too large, assume signed 64-bit. Negative track fragment decode times are invalid, but they exist in the wild.
              // This prevents large values from being used for initPTS, which can cause playlist sync issues.
              // https://github.com/video-dev/hls.js/issues/5303
              if (baseTime === UINT32_MAX) {
                logger.warn(
                  `[mp4-demuxer]: Ignoring assumed invalid signed 64-bit track fragment decode time`
                );
                return result;
              }
              baseTime *= UINT32_MAX + 1;
              baseTime += readUint32(tfdt, 8);
            }
            // assume a 90kHz clock if no timescale was specified
            const scale = track.timescale || 90e3;
            // convert base time to seconds
            const startTime = baseTime / scale;
            if (
              isFinite(startTime) &&
              (result === null || startTime < result)
            ) {
              return startTime;
            }
          }
          return result;
        },
        null
      );
      if (
        start !== null &&
        isFinite(start) &&
        (result === null || start < result)
      ) {
        return start;
      }
      return result;
    },
    null
  );
}

/*
  For Reference:
  aligned(8) class TrackFragmentHeaderBox
           extends FullBox(‘tfhd’, 0, tf_flags){
     unsigned int(32)  track_ID;
     // all the following are optional fields
     unsigned int(64)  base_data_offset;
     unsigned int(32)  sample_description_index;
     unsigned int(32)  default_sample_duration;
     unsigned int(32)  default_sample_size;
     unsigned int(32)  default_sample_flags
  }
 */
export function getDuration(data: Uint8Array, initData: InitData) {
  let rawDuration = 0;
  let videoDuration = 0;
  let audioDuration = 0;
  const trafs = findBox(data, ['moof', 'traf']);
  for (let i = 0; i < trafs.length; i++) {
    const traf = trafs[i];
    // There is only one tfhd & trun per traf
    // This is true for CMAF style content, and we should perhaps check the ftyp
    // and only look for a single trun then, but for ISOBMFF we should check
    // for multiple track runs.
    const tfhd = findBox(traf, ['tfhd'])[0];
    // get the track id from the tfhd
    const id = readUint32(tfhd, 4);
    const track = initData[id];
    if (!track) {
      continue;
    }
    const trackDefault = track.default;
    const tfhdFlags = readUint32(tfhd, 0) | trackDefault?.flags!;
    let sampleDuration: number | undefined = trackDefault?.duration;
    if (tfhdFlags & 0x000008) {
      // 0x000008 indicates the presence of the default_sample_duration field
      if (tfhdFlags & 0x000002) {
        // 0x000002 indicates the presence of the sample_description_index field, which precedes default_sample_duration
        // If present, the default_sample_duration exists at byte offset 12
        sampleDuration = readUint32(tfhd, 12);
      } else {
        // Otherwise, the duration is at byte offset 8
        sampleDuration = readUint32(tfhd, 8);
      }
    }
    // assume a 90kHz clock if no timescale was specified
    const timescale = track.timescale || 90e3;
    const truns = findBox(traf, ['trun']);
    for (let j = 0; j < truns.length; j++) {
      rawDuration = computeRawDurationFromSamples(truns[j]);
      if (!rawDuration && sampleDuration) {
        const sampleCount = readUint32(truns[j], 4);
        rawDuration = sampleDuration * sampleCount;
      }
      if (track.type === ElementaryStreamTypes.VIDEO) {
        videoDuration += rawDuration / timescale;
      } else if (track.type === ElementaryStreamTypes.AUDIO) {
        audioDuration += rawDuration / timescale;
      }
    }
  }
  if (videoDuration === 0 && audioDuration === 0) {
    // If duration samples are not available in the traf use sidx subsegment_duration
    let sidxDuration = 0;
    const sidxs = findBox(data, ['sidx']);
    for (let i = 0; i < sidxs.length; i++) {
      const sidx = parseSegmentIndex(sidxs[i]);
      if (sidx?.references) {
        sidxDuration += sidx.references.reduce(
          (dur, ref) => dur + ref.info.duration || 0,
          0
        );
      }
    }

    return sidxDuration;
  }
  if (videoDuration) {
    return videoDuration;
  }
  return audioDuration;
}

/*
  For Reference:
  aligned(8) class TrackRunBox
           extends FullBox(‘trun’, version, tr_flags) {
     unsigned int(32)  sample_count;
     // the following are optional fields
     signed int(32) data_offset;
     unsigned int(32)  first_sample_flags;
     // all fields in the following array are optional
     {
        unsigned int(32)  sample_duration;
        unsigned int(32)  sample_size;
        unsigned int(32)  sample_flags
        if (version == 0)
           { unsigned int(32)
        else
           { signed int(32)
     }[ sample_count ]
  }
 */
export function computeRawDurationFromSamples(trun): number {
  const flags = readUint32(trun, 0);
  // Flags are at offset 0, non-optional sample_count is at offset 4. Therefore we start 8 bytes in.
  // Each field is an int32, which is 4 bytes
  let offset = 8;
  // data-offset-present flag
  if (flags & 0x000001) {
    offset += 4;
  }
  // first-sample-flags-present flag
  if (flags & 0x000004) {
    offset += 4;
  }

  let duration = 0;
  const sampleCount = readUint32(trun, 4);
  for (let i = 0; i < sampleCount; i++) {
    // sample-duration-present flag
    if (flags & 0x000100) {
      const sampleDuration = readUint32(trun, offset);
      duration += sampleDuration;
      offset += 4;
    }
    // sample-size-present flag
    if (flags & 0x000200) {
      offset += 4;
    }
    // sample-flags-present flag
    if (flags & 0x000400) {
      offset += 4;
    }
    // sample-composition-time-offsets-present flag
    if (flags & 0x000800) {
      offset += 4;
    }
  }
  return duration;
}

export function offsetStartDTS(
  initData: InitData,
  fmp4: Uint8Array,
  timeOffset: number
) {
  findBox(fmp4, ['moof', 'traf']).forEach((traf) => {
    findBox(traf, ['tfhd']).forEach((tfhd) => {
      // get the track id from the tfhd
      const id = readUint32(tfhd, 4);
      const track = initData[id];
      if (!track) {
        return;
      }
      // assume a 90kHz clock if no timescale was specified
      const timescale = track.timescale || 90e3;
      // get the base media decode time from the tfdt
      findBox(traf, ['tfdt']).forEach((tfdt) => {
        const version = tfdt[0];
        let baseMediaDecodeTime = readUint32(tfdt, 4);

        if (version === 0) {
          baseMediaDecodeTime -= timeOffset * timescale;
          baseMediaDecodeTime = Math.max(baseMediaDecodeTime, 0);
          writeUint32(tfdt, 4, baseMediaDecodeTime);
        } else {
          baseMediaDecodeTime *= Math.pow(2, 32);
          baseMediaDecodeTime += readUint32(tfdt, 8);
          baseMediaDecodeTime -= timeOffset * timescale;
          baseMediaDecodeTime = Math.max(baseMediaDecodeTime, 0);
          const upper = Math.floor(baseMediaDecodeTime / (UINT32_MAX + 1));
          const lower = Math.floor(baseMediaDecodeTime % (UINT32_MAX + 1));
          writeUint32(tfdt, 4, upper);
          writeUint32(tfdt, 8, lower);
        }
      });
    });
  });
}

// TODO: Check if the last moof+mdat pair is part of the valid range
export function segmentValidRange(data: Uint8Array): SegmentedRange {
  const segmentedRange: SegmentedRange = {
    valid: null,
    remainder: null,
  };

  const moofs = findBox(data, ['moof']);
  if (!moofs) {
    return segmentedRange;
  } else if (moofs.length < 2) {
    segmentedRange.remainder = data;
    return segmentedRange;
  }
  const last = moofs[moofs.length - 1];
  // Offset by 8 bytes; findBox offsets the start by as much
  segmentedRange.valid = sliceUint8(data, 0, last.byteOffset - 8);
  segmentedRange.remainder = sliceUint8(data, last.byteOffset - 8);
  return segmentedRange;
}

export interface SegmentedRange {
  valid: Uint8Array | null;
  remainder: Uint8Array | null;
}

export function appendUint8Array(
  data1: Uint8Array,
  data2: Uint8Array
): Uint8Array {
  const temp = new Uint8Array(data1.length + data2.length);
  temp.set(data1);
  temp.set(data2, data1.length);

  return temp;
}

export interface IEmsgParsingData {
  schemeIdUri: string;
  value: string;
  timeScale: number;
  presentationTimeDelta?: number;
  presentationTime?: number;
  eventDuration: number;
  id: number;
  payload: Uint8Array;
}

export function parseSamples(
  timeOffset: number,
  track: PassthroughTrack
): UserdataSample[] {
  const seiSamples = [] as UserdataSample[];
  const videoData = track.samples;
  const timescale = track.timescale;
  const trackId = track.id;
  let isHEVCFlavor = false;

  const moofs = findBox(videoData, ['moof']);
  moofs.map((moof) => {
    const moofOffset = moof.byteOffset - 8;
    const trafs = findBox(moof, ['traf']);
    trafs.map((traf) => {
      // get the base media decode time from the tfdt
      const baseTime = findBox(traf, ['tfdt']).map((tfdt) => {
        const version = tfdt[0];
        let result = readUint32(tfdt, 4);
        if (version === 1) {
          result *= Math.pow(2, 32);
          result += readUint32(tfdt, 8);
        }
        return result / timescale;
      })[0];

      if (baseTime !== undefined) {
        timeOffset = baseTime;
      }

      return findBox(traf, ['tfhd']).map((tfhd) => {
        const id = readUint32(tfhd, 4);
        const tfhdFlags = readUint32(tfhd, 0) & 0xffffff;
        const baseDataOffsetPresent = (tfhdFlags & 0x000001) !== 0;
        const sampleDescriptionIndexPresent = (tfhdFlags & 0x000002) !== 0;
        const defaultSampleDurationPresent = (tfhdFlags & 0x000008) !== 0;
        let defaultSampleDuration = 0;
        const defaultSampleSizePresent = (tfhdFlags & 0x000010) !== 0;
        let defaultSampleSize = 0;
        const defaultSampleFlagsPresent = (tfhdFlags & 0x000020) !== 0;
        let tfhdOffset = 8;

        if (id === trackId) {
          if (baseDataOffsetPresent) {
            tfhdOffset += 8;
          }
          if (sampleDescriptionIndexPresent) {
            tfhdOffset += 4;
          }
          if (defaultSampleDurationPresent) {
            defaultSampleDuration = readUint32(tfhd, tfhdOffset);
            tfhdOffset += 4;
          }
          if (defaultSampleSizePresent) {
            defaultSampleSize = readUint32(tfhd, tfhdOffset);
            tfhdOffset += 4;
          }
          if (defaultSampleFlagsPresent) {
            tfhdOffset += 4;
          }
          if (track.type === 'video') {
            isHEVCFlavor = isHEVC(track.codec);
          }

          findBox(traf, ['trun']).map((trun) => {
            const version = trun[0];
            const flags = readUint32(trun, 0) & 0xffffff;
            const dataOffsetPresent = (flags & 0x000001) !== 0;
            let dataOffset = 0;
            const firstSampleFlagsPresent = (flags & 0x000004) !== 0;
            const sampleDurationPresent = (flags & 0x000100) !== 0;
            let sampleDuration = 0;
            const sampleSizePresent = (flags & 0x000200) !== 0;
            let sampleSize = 0;
            const sampleFlagsPresent = (flags & 0x000400) !== 0;
            const sampleCompositionOffsetsPresent = (flags & 0x000800) !== 0;
            let compositionOffset = 0;
            const sampleCount = readUint32(trun, 4);
            let trunOffset = 8; // past version, flags, and sample count

            if (dataOffsetPresent) {
              dataOffset = readUint32(trun, trunOffset);
              trunOffset += 4;
            }
            if (firstSampleFlagsPresent) {
              trunOffset += 4;
            }

            let sampleOffset = dataOffset + moofOffset;

            for (let ix = 0; ix < sampleCount; ix++) {
              if (sampleDurationPresent) {
                sampleDuration = readUint32(trun, trunOffset);
                trunOffset += 4;
              } else {
                sampleDuration = defaultSampleDuration;
              }
              if (sampleSizePresent) {
                sampleSize = readUint32(trun, trunOffset);
                trunOffset += 4;
              } else {
                sampleSize = defaultSampleSize;
              }
              if (sampleFlagsPresent) {
                trunOffset += 4;
              }
              if (sampleCompositionOffsetsPresent) {
                if (version === 0) {
                  compositionOffset = readUint32(trun, trunOffset);
                } else {
                  compositionOffset = readSint32(trun, trunOffset);
                }
                trunOffset += 4;
              }
              if (track.type === ElementaryStreamTypes.VIDEO) {
                let naluTotalSize = 0;
                while (naluTotalSize < sampleSize) {
                  const naluSize = readUint32(videoData, sampleOffset);
                  sampleOffset += 4;
                  if (isSEIMessage(isHEVCFlavor, videoData[sampleOffset])) {
                    const data = videoData.subarray(
                      sampleOffset,
                      sampleOffset + naluSize
                    );
                    parseSEIMessageFromNALu(
                      data,
                      isHEVCFlavor ? 2 : 1,
                      timeOffset + compositionOffset / timescale,
                      seiSamples
                    );
                  }
                  sampleOffset += naluSize;
                  naluTotalSize += naluSize + 4;
                }
              }

              timeOffset += sampleDuration / timescale;
            }
          });
        }
      });
    });
  });
  return seiSamples;
}

function isHEVC(codec: string) {
  if (!codec) {
    return false;
  }
  const delimit = codec.indexOf('.');
  const baseCodec = delimit < 0 ? codec : codec.substring(0, delimit);
  return (
    baseCodec === 'hvc1' ||
    baseCodec === 'hev1' ||
    // Dolby Vision
    baseCodec === 'dvh1' ||
    baseCodec === 'dvhe'
  );
}

function isSEIMessage(isHEVCFlavor: boolean, naluHeader: number) {
  if (isHEVCFlavor) {
    const naluType = (naluHeader >> 1) & 0x3f;
    return naluType === 39 || naluType === 40;
  } else {
    const naluType = naluHeader & 0x1f;
    return naluType === 6;
  }
}

export function parseSEIMessageFromNALu(
  unescapedData: Uint8Array,
  headerSize: number,
  pts: number,
  samples: UserdataSample[]
) {
  const data = discardEPB(unescapedData);
  let seiPtr = 0;
  // skip nal header
  seiPtr += headerSize;
  let payloadType = 0;
  let payloadSize = 0;
  let endOfCaptions = false;
  let b = 0;

  while (seiPtr < data.length) {
    payloadType = 0;
    do {
      if (seiPtr >= data.length) {
        break;
      }
      b = data[seiPtr++];
      payloadType += b;
    } while (b === 0xff);

    // Parse payload size.
    payloadSize = 0;
    do {
      if (seiPtr >= data.length) {
        break;
      }
      b = data[seiPtr++];
      payloadSize += b;
    } while (b === 0xff);

    const leftOver = data.length - seiPtr;

    if (!endOfCaptions && payloadType === 4 && seiPtr < data.length) {
      endOfCaptions = true;

      const countryCode = data[seiPtr++];
      if (countryCode === 181) {
        const providerCode = readUint16(data, seiPtr);
        seiPtr += 2;

        if (providerCode === 49) {
          const userStructure = readUint32(data, seiPtr);
          seiPtr += 4;

          if (userStructure === 0x47413934) {
            const userDataType = data[seiPtr++];

            // Raw CEA-608 bytes wrapped in CEA-708 packet
            if (userDataType === 3) {
              const firstByte = data[seiPtr++];
              const totalCCs = 0x1f & firstByte;
              const enabled = 0x40 & firstByte;
              const totalBytes = enabled ? 2 + totalCCs * 3 : 0;
              const byteArray = new Uint8Array(totalBytes);
              if (enabled) {
                byteArray[0] = firstByte;
                for (let i = 1; i < totalBytes; i++) {
                  byteArray[i] = data[seiPtr++];
                }
              }

              samples.push({
                type: userDataType,
                payloadType,
                pts,
                bytes: byteArray,
              });
            }
          }
        }
      }
    } else if (payloadType === 5 && payloadSize < leftOver) {
      endOfCaptions = true;

      if (payloadSize > 16) {
        const uuidStrArray: Array<string> = [];
        for (let i = 0; i < 16; i++) {
          const b = data[seiPtr++].toString(16);
          uuidStrArray.push(b.length == 1 ? '0' + b : b);

          if (i === 3 || i === 5 || i === 7 || i === 9) {
            uuidStrArray.push('-');
          }
        }
        const length = payloadSize - 16;
        const userDataBytes = new Uint8Array(length);
        for (let i = 0; i < length; i++) {
          userDataBytes[i] = data[seiPtr++];
        }

        samples.push({
          payloadType,
          pts,
          uuid: uuidStrArray.join(''),
          userData: utf8ArrayToStr(userDataBytes),
          userDataBytes,
        });
      }
    } else if (payloadSize < leftOver) {
      seiPtr += payloadSize;
    } else if (payloadSize > leftOver) {
      break;
    }
  }
}

/**
 * remove Emulation Prevention bytes from a RBSP
 */
export function discardEPB(data: Uint8Array): Uint8Array {
  const length = data.byteLength;
  const EPBPositions = [] as Array<number>;
  let i = 1;

  // Find all `Emulation Prevention Bytes`
  while (i < length - 2) {
    if (data[i] === 0 && data[i + 1] === 0 && data[i + 2] === 0x03) {
      EPBPositions.push(i + 2);
      i += 2;
    } else {
      i++;
    }
  }

  // If no Emulation Prevention Bytes were found just return the original
  // array
  if (EPBPositions.length === 0) {
    return data;
  }

  // Create a new array to hold the NAL unit data
  const newLength = length - EPBPositions.length;
  const newData = new Uint8Array(newLength);
  let sourceIndex = 0;

  for (i = 0; i < newLength; sourceIndex++, i++) {
    if (sourceIndex === EPBPositions[0]) {
      // Skip this byte
      sourceIndex++;
      // Remove this position index
      EPBPositions.shift();
    }
    newData[i] = data[sourceIndex];
  }
  return newData;
}

export function parseEmsg(data: Uint8Array): IEmsgParsingData {
  const version = data[0];
  let schemeIdUri: string = '';
  let value: string = '';
  let timeScale: number = 0;
  let presentationTimeDelta: number = 0;
  let presentationTime: number = 0;
  let eventDuration: number = 0;
  let id: number = 0;
  let offset: number = 0;

  if (version === 0) {
    while (bin2str(data.subarray(offset, offset + 1)) !== '\0') {
      schemeIdUri += bin2str(data.subarray(offset, offset + 1));
      offset += 1;
    }

    schemeIdUri += bin2str(data.subarray(offset, offset + 1));
    offset += 1;

    while (bin2str(data.subarray(offset, offset + 1)) !== '\0') {
      value += bin2str(data.subarray(offset, offset + 1));
      offset += 1;
    }

    value += bin2str(data.subarray(offset, offset + 1));
    offset += 1;

    timeScale = readUint32(data, 12);
    presentationTimeDelta = readUint32(data, 16);
    eventDuration = readUint32(data, 20);
    id = readUint32(data, 24);
    offset = 28;
  } else if (version === 1) {
    offset += 4;
    timeScale = readUint32(data, offset);
    offset += 4;
    const leftPresentationTime = readUint32(data, offset);
    offset += 4;
    const rightPresentationTime = readUint32(data, offset);
    offset += 4;
    presentationTime = 2 ** 32 * leftPresentationTime + rightPresentationTime;
    if (!Number.isSafeInteger(presentationTime)) {
      presentationTime = Number.MAX_SAFE_INTEGER;
      logger.warn(
        'Presentation time exceeds safe integer limit and wrapped to max safe integer in parsing emsg box'
      );
    }

    eventDuration = readUint32(data, offset);
    offset += 4;
    id = readUint32(data, offset);
    offset += 4;

    while (bin2str(data.subarray(offset, offset + 1)) !== '\0') {
      schemeIdUri += bin2str(data.subarray(offset, offset + 1));
      offset += 1;
    }

    schemeIdUri += bin2str(data.subarray(offset, offset + 1));
    offset += 1;

    while (bin2str(data.subarray(offset, offset + 1)) !== '\0') {
      value += bin2str(data.subarray(offset, offset + 1));
      offset += 1;
    }

    value += bin2str(data.subarray(offset, offset + 1));
    offset += 1;
  }
  const payload = data.subarray(offset, data.byteLength);

  return {
    schemeIdUri,
    value,
    timeScale,
    presentationTime,
    presentationTimeDelta,
    eventDuration,
    id,
    payload,
  };
}

export function mp4Box(type: ArrayLike<number>, ...payload: Uint8Array[]) {
  const len = payload.length;
  let size = 8;
  let i = len;
  while (i--) {
    size += payload[i].byteLength;
  }
  const result = new Uint8Array(size);
  result[0] = (size >> 24) & 0xff;
  result[1] = (size >> 16) & 0xff;
  result[2] = (size >> 8) & 0xff;
  result[3] = size & 0xff;
  result.set(type, 4);
  for (i = 0, size = 8; i < len; i++) {
    result.set(payload[i], size);
    size += payload[i].byteLength;
  }
  return result;
}

export function mp4pssh(
  systemId: Uint8Array,
  keyids: Array<Uint8Array> | null,
  data: Uint8Array
) {
  if (systemId.byteLength !== 16) {
    throw new RangeError('Invalid system id');
  }
  let version;
  let kids;
  if (keyids) {
    version = 1;
    kids = new Uint8Array(keyids.length * 16);
    for (let ix = 0; ix < keyids.length; ix++) {
      const k = keyids[ix]; // uint8array
      if (k.byteLength !== 16) {
        throw new RangeError('Invalid key');
      }
      kids.set(k, ix * 16);
    }
  } else {
    version = 0;
    kids = new Uint8Array();
  }
  let kidCount;
  if (version > 0) {
    kidCount = new Uint8Array(4);
    if (keyids!.length > 0) {
      new DataView(kidCount.buffer).setUint32(0, keyids!.length, false);
    }
  } else {
    kidCount = new Uint8Array();
  }
  const dataSize = new Uint8Array(4);
  if (data && data.byteLength > 0) {
    new DataView(dataSize.buffer).setUint32(0, data.byteLength, false);
  }
  return mp4Box(
    [112, 115, 115, 104],
    new Uint8Array([
      version,
      0x00,
      0x00,
      0x00, // Flags
    ]),
    systemId, // 16 bytes
    kidCount,
    kids,
    dataSize,
    data || new Uint8Array()
  );
}

export function parsePssh(initData: ArrayBuffer) {
  if (!(initData instanceof ArrayBuffer) || initData.byteLength < 32) {
    return null;
  }
  const result = {
    version: 0,
    systemId: '',
    kids: null as null | Uint8Array[],
    data: null as null | Uint8Array,
  };
  const view = new DataView(initData);
  const boxSize = view.getUint32(0);
  if (initData.byteLength !== boxSize && boxSize > 44) {
    return null;
  }
  const type = view.getUint32(4);
  if (type !== 0x70737368) {
    return null;
  }
  result.version = view.getUint32(8) >>> 24;
  if (result.version > 1) {
    return null;
  }
  result.systemId = Hex.hexDump(new Uint8Array(initData, 12, 16));
  const dataSizeOrKidCount = view.getUint32(28);
  if (result.version === 0) {
    if (boxSize - 32 < dataSizeOrKidCount) {
      return null;
    }
    result.data = new Uint8Array(initData, 32, dataSizeOrKidCount);
  } else if (result.version === 1) {
    result.kids = [];
    for (let i = 0; i < dataSizeOrKidCount; i++) {
      result.kids.push(new Uint8Array(initData, 32 + i * 16, 16));
    }
  }
  return result;
}

function mimeTypeBuilderHEVC(
  codecName: string,
  codecDetails: hvcConfigurationRecord
): string {
  const generalProfileSpaceMap = ['', 'A', 'B', 'C'];
  let codecMimeType = codecName;
  if (codecDetails) {
    codecMimeType += '.';
    codecMimeType += generalProfileSpaceMap[codecDetails.generalProfileSpace];
    codecMimeType += codecDetails.generalProfileIdc;

    codecMimeType += '.';
    codecMimeType += codecDetails.generalProfileCompatibility.toString(16)[0];

    codecMimeType += '.';
    codecMimeType += codecDetails.generalTierFlag === 0 ? 'L' : 'H';
    codecMimeType += codecDetails.generalLevelIdc;

    let constraintString = '';
    const lastByteIndex = (
      codecDetails.generalConstraintIndicator as any
    ).findLastIndex((x: Number) => x !== 0);
    if (lastByteIndex !== -1) {
      constraintString =
        '.' +
        (
          codecDetails.generalConstraintIndicator.slice(
            0,
            lastByteIndex + 1
          ) as any
        )
          .map((x: Number) => x.toString(16))
          .join('.');
    }

    codecMimeType += constraintString;
  }
  return codecMimeType;
}

function parseDataReferenceIndex(data: Uint8Array) {
  // UInt8[6] reserved
  return readUint16(data, 6);
}

interface visualSampleEntry {
  dataReferenceIndex: number;
  width: number;
  height: number;
  horizResolution: number;
  vertResolution: number;
  frameCount: number;
  compressorName: string;
  depth: number;
  end: number;
}

function parseVisualSampleEntry(data: Uint8Array): visualSampleEntry {
  return {
    dataReferenceIndex: parseDataReferenceIndex(data),

    // UInt16 preDefined
    // UInt16 reserved
    // UInt32[3] preDefined

    width: readUint16(data, 24),
    height: readUint16(data, 26),

    horizResolution: readUint32(data, 28), // 0x00480000 - 72 dpi
    vertResolution: readUint32(data, 32), // 0x00480000 - 72 dpi

    // UInt32 reserved

    frameCount: readUint16(data, 40),
    compressorName: bin2str(data.subarray(43, Math.min(data[42], 31))),
    depth: readUint16(data, 74),

    // UInt16 preDefined

    end: 78,
  };
}

interface hvcConfigurationRecord {
  configurationVersion: number;
  generalProfileSpace: number;
  generalTierFlag: number;
  generalProfileIdc: number;
  generalProfileCompatibility: number;
  generalConstraintIndicator: Uint8Array;
  generalLevelIdc: number;
  minSpatialSegmentationIdc: number;
  parallelismType: number;
  chromaFormatIdc: number;
  bitDepthLumaMinus8: number;
  bitDepthChromaMinus8: number;
  avgFrameRate: number;
  constantFrameRate: number;
  numTemporalLayers: number;
  temporalIdNested: number;
  lengthSizeMinusOne: number;
  naluArrays: Array<object>;
}

function parseHvcConfigurationRecord(data: Uint8Array): hvcConfigurationRecord {
  return {
    configurationVersion: data[0],
    generalProfileSpace: data[1] >> 6,
    generalTierFlag: (data[1] & 0x20) >> 5,
    generalProfileIdc: data[1] & 0x1f,
    generalProfileCompatibility: readUint32(data, 2),
    generalConstraintIndicator: data.subarray(6, 12),
    generalLevelIdc: data[12],
    minSpatialSegmentationIdc: readUint16(data, 13) & 0xfff,
    parallelismType: data[15] & 0x3,
    chromaFormatIdc: data[16] & 0x3,
    bitDepthLumaMinus8: data[17] & 0x7,
    bitDepthChromaMinus8: data[18] & 0x7,
    avgFrameRate: readUint16(data, 19),
    constantFrameRate: data[21] >> 6,
    numTemporalLayers: (data[21] & 0xd) >> 3,
    temporalIdNested: (data[21] & 0x4) >> 2,
    lengthSizeMinusOne: data[21] & 0x3,
    naluArrays: [],
  };
}