[Mp4-tech] [Audio] About down sampling in HE-AAC

[Dattaguru B.N.]

Dear All,
I am working on HE-AAC Decoder.
I have understood by studying the Standard (N5570)
that, the down sampling is required in case of levels
3 & 4.  
My questions are 
1. what about the levels 2 & 5?  
2. Is down sampling is optional for these levels? 
3. Is that down sampling is not required for 2 & 5?
4. Where can I get the level information? Is it at    
   the header extraction or user specified?
5. Where can I get the down sampling information in   
   the bit stream?
Thanks in advance
Dattaguru 
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