View source for Decoding AAC FIL

''Part of [[Understanding AAC]]''

This can apparently be used for extension data since libfaad2 checks for SBR data in the FIL chunk which is known to be applicable to later HE-AAC variants. There are other extension data types in the syntax. According to the libfaad2 logic, a FIL element can have either an SBR chunk or a series of other extension types. These are the defined extension types:

* 1: FILL_DATA
* 2: DATA_ELEMENT
* 11: DYNAMIC_RANGE
* 12: SBR_DATA
* 13: SBR_DATA_CRC

  local count
  local extra_count
  local extension_type
  4 bits: count
  if (count == 15)
    8 bits: extra_count
  count += extra_count
  4 bits: extension_type

FILL_DATA:
  4 bits:  must be 0000b
  foreach 0..count-2
    8 bits: must be 0xA5 (10100101b)

DATA_ELEMENT:
'''[unfinished]'''

DYNAMIC_RANGE:
'''[unfinished]'''

SBR_DATA:
'''[unfinished]'''

SBR_DATA_CRC:
'''[unfinished]'''