function createSeekHead() {
      let seekPositionEBMLTemplate = {
        'id': 0x53AC,  // SeekPosition
        'size': 5,     // Allows for 32GB video files
        'data': 0      // We'll overwrite this when the file is complete
      },

          result = {
            'id': 0x114D9B74,  // SeekHead
            'data': []
          };

      for (let name in seekPoints) {
        let seekPoint = seekPoints[name];

        seekPoint.positionEBML = Object.create(seekPositionEBMLTemplate);

        result.data.push({
          'id': 0x4DBB,  // Seek
          'data': [
            {
              'id': 0x53AB,  // SeekID
              'data': seekPoint.id
            },
            seekPoint.positionEBML
          ]
        });
      }

      return result;
    }
Create a SeekHead element with descriptors for the points in the global
seekPoints array.

5 bytes of position values are reserved for each node, which lie at the
offset point.positionEBML.dataOffset, to be overwritten later.