FreeCalypso > hg > gsm-codec-lib
view libgsmefr/pre_proc.c @ 78:5bc228bb421e
libgsmefr: lsp_az.c compiles
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Sat, 26 Nov 2022 06:54:06 +0000 |
parents | 49dd1ac8e75b |
children | 3ea19a9aa2a1 |
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/************************************************************************* * * FUNCTION: Pre_Process() * * PURPOSE: Preprocessing of input speech. * * DESCRIPTION: * - 2nd order high pass filtering with cut off frequency at 80 Hz. * - Divide input by two. * *************************************************************************/ #include "typedef.h" #include "basic_op.h" #include "oper_32b.h" #include "count.h" /*------------------------------------------------------------------------* * * * Algorithm: * * * * y[i] = b[0]*x[i]/2 + b[1]*x[i-1]/2 + b[2]*x[i-2]/2 * * + a[1]*y[i-1] + a[2]*y[i-2]; * * * * * * Input is divided by two in the filtering process. * *------------------------------------------------------------------------*/ /* filter coefficients (fc = 80 Hz, coeff. b[] is divided by 2) */ static const Word16 b[3] = {1899, -3798, 1899}; static const Word16 a[3] = {4096, 7807, -3733}; /* Static values to be preserved between calls */ /* y[] values are kept in double precision */ static Word16 y2_hi, y2_lo, y1_hi, y1_lo, x0, x1; /* Initialization of static values */ void Init_Pre_Process (void) { y2_hi = 0; y2_lo = 0; y1_hi = 0; y1_lo = 0; x0 = 0; x1 = 0; } void Pre_Process ( Word16 signal[], /* input/output signal */ Word16 lg) /* lenght of signal */ { Word16 i, x2; Word32 L_tmp; for (i = 0; i < lg; i++) { x2 = x1; move16 (); x1 = x0; move16 (); x0 = signal[i]; move16 (); /* y[i] = b[0]*x[i]/2 + b[1]*x[i-1]/2 + b140[2]*x[i-2]/2 */ /* + a[1]*y[i-1] + a[2] * y[i-2]; */ L_tmp = Mpy_32_16 (y1_hi, y1_lo, a[1]); L_tmp = L_add (L_tmp, Mpy_32_16 (y2_hi, y2_lo, a[2])); L_tmp = L_mac (L_tmp, x0, b[0]); L_tmp = L_mac (L_tmp, x1, b[1]); L_tmp = L_mac (L_tmp, x2, b[2]); L_tmp = L_shl (L_tmp, 3); signal[i] = round (L_tmp); move16 (); y2_hi = y1_hi; move16 (); y2_lo = y1_lo; move16 (); L_Extract (L_tmp, &y1_hi, &y1_lo); } return; }