[Mp4-tech] Compatibility of Mpeg-4 AAC.

[Ralph Sperschneider]

岡本光平 wrote:
> Hello Everyone,
> 
>  I've read this brochure of "What's AAC?" on the mp4 Industry Forum page.
> It declares the Mpeg-*4* AAC as the "Most powerful audio codec..." , 
> and lists as a reason that my country has chosen Mpeg-*2* AAC for digital broadcast.
> 
>  Does this mean that the Mpeg-*4* AAC covers the Mpeg-*2* AAC entirely?
> Is a Mpeg-*4* AAC supported device able to encode/decode Mpeg-*2* AAC content?
> 
> Regard,
> Kohei Okamoto
> 

Dear Kohei,
your assumption is exactly true. The MPEG-2 AAC profiles have been reused and 
became Audio Object Types in MPEG-4 Audio. Hence, any MPEG-4 Audio decor that 
supports those MPEG-4 Audio Object types is generally able to decode data 
encoded using the corresponding MPEG-2 AAC profiles.
Best regards,
Ralph
-- 
Dipl.-Ing. Ralph Sperschneider  | Phone: +49 9131 776 344
Fraunhofer-IIS                  | Fax:   +49 9131 776 398
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