[M4IF Technotes] Re: AAC: PNS scale factors

[Ralph Sperschneider]

John Cox wrote:
> Dear Ralph
> 
> 
>>>Ideally there would by synced 'random' number generators in the encoder
>>>and decoder so the encoder knows exactly what to expect, in which case
>>>there would be no need for the final renormalization.
>>
>>I guess you agree with me that this is a theoretical approach only. ;-)
> 
> 
> Given the current protocol it has got to be theoretical only. However
> the only extension required is a single bit to reset the 'random number'
> generator to a known state.  After that you define a random number
> generator (say random2 from the reference software) in the standard.  A
> profile requirement to set the 'reset' bit once every (say) 8 frames
> should make it all work.  This is a lot less complex to do than the
> standard prediction tool.

Dear Yohn,
I get your point, but please consider that the standard is already out there 
without such a requirement. Adding this would not only make any decoder 
unconform (due to the not considered reset and the not specified random 
generator), but would also make any available encoder and mp4 audio data invalid 
that utilizes PNS (due to the additional bit).
Best regards,
Ralph
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Dipl.-Ing. Ralph Sperschneider  | Phone: +49 9131 776 344
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