hunk_offset[0] = 797
                                    chunk_offset[1] = 13096
                                [sgpd: Sample Group Description Box]
                                    position = 694
                                    size = 26
                                    version = 1
                                    flags = 0x000000
                                    grouping_type = roll
                                    default_length = 2 (constant)
                                    entry