[Mp4-tech] [Audio]QMF filtering in non SBR AAC bit streams

[Dattaguru B.N.]

Dear All,
I am working on HE AAC decoder for LC profile (SBR +
LC).  
I want to write a decoder which will support both
AAC-LC and HE-AAC LC.  If I provide, AAC LC bit
streams, I feel I will get degradation in the
quality!!!!! This is because, there will be a QMF
filter bank in the post processing stage i.e., SBR
decoding.  As my decoder should support both,  I
cannot eliminate this part and in practical situation
I will not know which bit stream will be fed as input
(e.g., it may be either normal AAC-LC or HE AAC LC).
Can anybody please let me know whether it is needed to
apply QMF filter bank, when I give the input non SBR
AACLC bit streams? 
Thanks in advance,
Dattaguru B.N. Vasista
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