[Mp4-tech] Re: [Audio] ADTS

[Ralph Sperschneider]

Saptarshi Ghosh wrote:
> Hi all,
> Could anyone please answer the following two
> questions:
> 
> Question 1.
> Is it necessary to overlap/add the raw data blocks in
> a SINGLE ADTS frame with the raw data blocks in any
> other frame or can the data in a SINGLE frame be
> decoded independently ?

not the raw data blocks but the 2048 decoded samples need to be processed using 
overlap and add. This is true for AAC independently on the transport or storage 
format. It is due to the nature of the MDCT/IMDCT.
> 
> Question 2.
> For crc checking, CRC16 polynomial 0x1021 is used. In
> this respect, please clarify the following parameters
> of the crc algorithm used:
> 
> 1. Initial value of 16-bit register when the algorithm
> starts
> 2. Whether each byte is reflected before it is
> processed
> 3. Whether the final register value is to be reflected
> 4. Whether any 16-bit number is to be XORed to the
> final register value
> 5. The checksum for the data string "123456789" as
> produced by this algorithm.

I would suggst that you check out the example implementation available in the 
referene software.
Best regards,
Ralph
-- 
Dipl.-Ing. Ralph Sperschneider  | Phone: +49 9131 776 344
Fraunhofer IIS                  | Fax:   +49 9131 776 398
Am Wolfsmantel 33               | mailto:ralph.sperschneider iis.fraunhofer.de
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