isobmff-inspector/src/boxes/mvhd.js

Simple ISOBMFF parser, compatible with JavaScript and Node.JS

export default {
  name: "Movie Header Box",
  description: "This box defines overall information which is " +
  "media‐independent, and relevant to the entire presentation " +
  "considered as a whole.",
  content: [
    {
      name: "version",
      description: "mvhd version",
      key: "version",
    },
    {
      name: "flags",
      description: "mvhd flags",
      key: "flags",
    },
    {
      name: "creation_time",
      description: "An integer that declares the creation time of the " +
       "presentation (in seconds since midnight, Jan. 1, 1904, in UTC time)",
      key: "creationTime",
    },
    {
      name: "modification_time",
      description: "An integer that declares the most recent time the " +
      "presentation was modified (in seconds since midnight, Jan. 1, 1904, " +
      "in UTC time)",
      key: "modificationTime",
    },
    {
      name: "timescale",
      description: "An integer that specifies the time‐scale for the entire " +
        "presentation; this is the number of time units that pass in one second. " +
        "For example, a t me coordinate system that measures time in sixtieths " +
        "of a second has a time scale of 60.",
      key: "timescale",
    },
    {
      name: "duration",
      description: "An integer that declares length of the presentation (in the " +
        "indicated timescale). This property is derived from the presentation’s " +
        "tracks: the value of this field corresponds to the duration of the " +
        "longest track in the presentation. If the durat ion cannot be " +
        "determined then duration is set to all 1s.",
      key: "duration",
    },
    {
      name: "rate",
      description: "A fixed point 16.16 number that indicates the preferred " +
        "rate to play the presentation; 1.0 (0x00010000) is normal forward playback ",
      key: "rate",
    },
    {
      name: "volume",
      description: "A fixed point 8.8 number that indicates the preferred playback " +
        "volume. 1.0 (0x0100) is full volume.",
      key: "volume",
    },
    {
      name: "reserved 1",
      description: "Reserved 16 bits",
      key: "reserved1",
    },
    {
      name: "reserved 2",
      description: "Reserved 2*32 bits",
      key: "reserved2",
    },
    {
      name: "matrix",
      description: "Provides a transformation matrix for the video; (u,v,w) are " +
        " restricted here to (0,0,1), hex values (0,0,0x40000000).",
      key: "matrix",
    },
    {
      name: "pre-defined",
      description: "Pre-defined 32*6 bits.",
      key: "predefined",
    },
    {
      name: "next_track_ID",
      description: "A non‐zero integer that indicates a value to use for the " +
        "track ID of the next track to be added to this presentation. " +
        "Zero is not a valid track ID value. The value of next_track_ID shall " +
        "be larger than the largest track‐ID in use. If this valu e is equal to " +
        "all 1s (32‐bit maxint), and a new media track is to be added, then a " +
        "search must be made in the file for an unused track identifier.",
      key: "nextTrackId",
    },
  ],

  parser: (reader) => {
    const version = reader.bytesToInt(1);
    if (version > 1) {
      throw new Error("invalid version");
    }

    const flags = reader.bytesToInt(3);

    let creationTime, modificationTime, timescale, duration;
    if (version === 1) {
      creationTime = reader.bytesToInt(8);
      modificationTime = reader.bytesToInt(8);
      timescale = reader.bytesToInt(4);
      duration = reader.bytesToInt(8);
    } else {
      creationTime = reader.bytesToInt(4);
      modificationTime = reader.bytesToInt(4);
      timescale = reader.bytesToInt(4);
      duration = reader.bytesToInt(4);
    }

    const rate = [
      reader.bytesToInt(2),
      reader.bytesToInt(2),
    ].join(".");

    const volume = [
      reader.bytesToInt(1),
      reader.bytesToInt(1),
    ].join(".");

    const reserved1 = reader.bytesToInt(2);
    const reserved2 = [
      reader.bytesToInt(4),
      reader.bytesToInt(4),
    ];

    const matrixArr = [];
    for (let i = 0; i < 9; i++) {
      matrixArr.push(reader.bytesToInt(4));
    }

    const predefined = [
      reader.bytesToInt(4),
      reader.bytesToInt(4),
      reader.bytesToInt(4),
      reader.bytesToInt(4),
      reader.bytesToInt(4),
      reader.bytesToInt(4),
    ];

    const nextTrackId = reader.bytesToInt(4);

    return {
      version,
      flags,
      creationTime,
      modificationTime,
      timescale,
      duration,
      rate,
      volume,
      reserved1,
      reserved2,
      matrix: matrixArr,
      predefined,
      nextTrackId,
    };
  },
};