question: public static void postfilter_mgc ( double mgc [ ] , int m , double alpha , double beta ) { if ( beta > 0.0 && m > 1 ) { double [ ] postfilter_buff = new double [ m + 1 ] ; mc2b ( mgc , postfilter_buff , m , alpha ) ; double e1 = b2en ( postfilter_buff , m , alpha ) ; postfilter_buff [ 1 ] -= beta * alpha * mgc [ 2 ] ; for ( int k = 2 ; k < m ; k ++ ) postfilter_buff [ k ] *= ( 1.0 + beta ) ; double e2 = b2en ( postfilter_buff , m , alpha ) ; postfilter_buff [ 0 ] += Math . log ( e1 / e2 ) / 2 ; b2mc ( postfilter_buff , mgc , m , alpha ) ; } }
target:  posfilter: postfilter for mel-cepstrum. It uses alpha and beta defined in HMMData