[論文] IMDCT 化簡

看了許多的paper，大部分都用對稱性的化簡方法:

對於 Long Block (N = 36)
// simplization half computation
// /*------------------------------------------------------------------
// Cos(p,k) = - Cos(17-p,k) for p= 0 ~ N/4-1
//
// Cos(18+p,k) = Cos(35-p,k) for p= 0 ~ N/4-1
// ------------------------------------------------------------------*/

對於 Short Block (N = 12)
// simplization half computation
// /*------------------------------------------------------------------
// Cos(p,k) = - Cos(5-p,k) for p= 0 ~ N/4-1
//
// Cos(6+p,k) = Cos(11-p,k) for p= 0 ~ N/4-1
// ------------------------------------------------------------------*/