(question) mpeg2 AAC encoder..TNS implementation

hi,
This is my first mail to this group
I am working on mpeg2 AAC encoder..
I need some help about implementation of Temporal noise shaping in 
that...
I found many articles about it, but not finding the essence for 
implementing it. 
 Can anyone give me its theory and information on how it works or 
else some good references..

I would be thankful to u  if I find a reply.

Wish you the success in ur field

Bye