For audio decoding, the butterfly unit determines combinations of components of a frequency domain vector to reduce {HEAD ~ the number} of {TAIL ~ multiplies} required to transform to the time domain  
of
For audio decoding , the butterfly unit determines combinations of components of a frequency domain vector to reduce { HEAD ~ the number } of { TAIL ~ multiplies } required to transform to the time domain
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH