Decoding AAC FIL

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]