[Mp4-tech] QMF Analysis

[MohanaRangan]

Hi,
I'm new to HE -AAC.Eventually I have a very basic doubt in QMF used in SBR,
hope it does not annoy you.
1) What is the Role of QMF ananlysis in SBR of HE-AAC ?
2) I understand QMF is like subband coding which maps time samples to
time,freq axis. After QMF also the samples are in time domain? Is it valis
for SBR ? if not why ?
3)What is the advantage/disadvantage of using QMF in HE -AAC rather than
Polyphase filter like MP3 ?
4)Is there any difference between the QMF used in HE-AAC SBR with respect to
any generic QMF based subband filtering?
regards,
Mohan