Purpose:
-Reduce dynamic range of interpolation filter coefficents from 8
bits to 7 bits.
-Inner product for 8-bit input data can be stored in a 16-bit signed
integer.

Impact on compression efficiency:
-Marginal improvement, typically less than 0.5% BDR.

Change-Id: I58d1408307ae7d2a6f9de8965c5877b258703199