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Topic: AAC - ADTS header using CRC? (Read 5999 times) previous topic - next topic
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AAC - ADTS header using CRC?

Hello all,

I need to test some AAC streams which are CRC protected.
Is there an AAC decoder that can decode ADTS header with CRC error protection (and hopefully report an error)?

Thanks,
Danijel

AAC - ADTS header using CRC?

Reply #1 –
Quote from: dand on
Hello all,

I need to test some AAC streams which are CRC protected.
Is there an AAC decoder that can decode ADTS header with CRC error protection (and hopefully report an error)?

Thanks,
Danijel

CRC error protection doesn't report an error. It automatically corrects an error. 

AAC - ADTS header using CRC?

Reply #2 –
Thank you kwwong, you've been very helpfull!


I also need some CRC protected ADTS sample streams. Is there an encoder I can create them with? Or is there a place I can download such samples?

Thanks again.

AAC - ADTS header using CRC?

Reply #3 –
I think the adif2mp4 tool in the reference code can convert ADIF files to ADTS files with CRC.

AAC - ADTS header using CRC?

Reply #4 –
It seems ISO reference decoder supports crc. Also, Winamp refuses to play streams with bad crc value.
 

AAC - ADTS header using CRC?

Reply #5 –
One problem.
ISO 14496-3 states:
"...first 192 bits of any channel_pair_element should be 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 algorithm I will protects 2nd ics in this cpe automaticaly. Do I then feed 2nd ics again into crc, this time as 128 bits?