[Mp4-tech] AAC - CRC protection

[Danijel Domazet]

Hi all,
One problem regarding AAC audio with ADTS header that uses CRC protection.
ISO 14496-3 states:
"...first 192 bits of any channel_pair_element should be CRC protected. In 
addition, the first 128 bits of 2nd individual_channel_stream in the 
channel_pair_element must be protected.
For any element where the specified protection length of 128 or 192 bits 
exceeds its actual length, the element is zero padded to the specified 
length for CRC calculation."
What happens when CPE is very short (~50 bits)? By feeding 192 bits of CPE 
to the CRC I will protects 2nd ICS in this CPE automaticaly. Do I then feed 
2nd ICS again into CRC calculator, this time as 128 bits?
Thanks,
Danijel Domazet