Kaitai NAL byte-stream parser

nal-byte-stream.ksy

meta:
  id: nal_byte_stream
  file-extension: h264
  endian: be
  license: CC0-1.0
doc-ref: https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-H.264-200305-S!!PDF-E&type=items
seq:
  - id: nal_byte_stream_segments
    type: nal_byte_stream_segment
    repeat: eos
types:
  nal_byte_stream_segment:
    seq:
    - id: start_code
      type: start_code
    - id: nal_unit
      type: nal_unit
  start_code:
    seq:
    - id: look_ahead
      type: start_code_look_ahead
    - id: start_code
      size: look_ahead.type_1 == 1 ? 3 : look_ahead.type_2 == 1 ? 4 : 0
  nal_unit:
    seq:
    - id: forbidden_zero_bit
      type: b1
    - id: nal_ref_idc
      type: b2
    - id: nal_unit_type
      type: b5
      enum: nal_unit_type
    - id: rbsp
      type: rbsp
  rbsp:
    seq:
    - id: payload_segment
      type: payload_segment
      repeat: until
      repeat-until: _.look_ahead.valid or _io.eof
  payload_segment:
    seq:
    - id: data
      size: 1
    - id: look_ahead
      type: start_code_look_ahead
  start_code_look_ahead:
    seq: []
    instances:
      type_1:
        pos: _io.pos
        type: b24
        if: _io.pos + 4 < _io.size
      type_2:
        pos: _io.pos
        type: u4
        if: _io.pos + 4 < _io.size
      valid:
        value: _io.pos + 4 < _io.size and (type_1 == 1 or type_2 == 1)
enums:
  nal_unit_type:
    1: slice_layer_without_partitioning
    2: slice_data_partition_a_layer
    3: slice_data_partition_b_layer
    4: slice_data_partition_c_layer
    5: slice_layer_without_partitioning
    6: sei
    7: seq_parameter_set
    8: pic_parameter_set
    9: access_unit_delimiter
    10: end_of_seq
    11: end_of_stream
    12: filler_data
    13: seq_parameter_set_extension
    14: prefix_nal_unit
    15: subset_seq_parameter_set
    19: slice_layer_without_partitioning
    20: slice_layer_extension
    21: slice_layer_extension_for_depth_view