FreeCalypso > hg > gsm-codec-lib
view libgsmefr/syn_filt.c @ 216:9d59df9b0e4e
amrconv: new program amr-ietf2cod
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Fri, 21 Apr 2023 21:28:02 +0000 |
parents | bb71c5414e71 |
children |
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/************************************************************************* * * FUNCTION: Syn_filt: * * PURPOSE: Perform synthesis filtering through 1/A(z). * *************************************************************************/ #include "gsm_efr.h" #include "typedef.h" #include "namespace.h" #include "basic_op.h" #include "no_count.h" #include "sig_proc.h" /* m = LPC order == 10 */ #define m 10 void Syn_filt ( Word16 a[], /* (i) : a[m+1] prediction coefficients (m=10) */ Word16 x[], /* (i) : input signal */ Word16 y[], /* (o) : output signal */ Word16 lg, /* (i) : size of filtering */ Word16 mem[], /* (i/o) : memory associated with this filtering. */ Word16 update /* (i) : 0=no update, 1=update of memory. */ ) { Word16 i, j; Word32 s; Word16 tmp[80]; /* This is usually done by memory allocation (lg+m) */ Word16 *yy; /* Copy mem[] to yy[] */ yy = tmp; move16 (); for (i = 0; i < m; i++) { *yy++ = mem[i]; move16 (); } /* Do the filtering. */ for (i = 0; i < lg; i++) { s = L_mult (x[i], a[0]); for (j = 1; j <= m; j++) { s = L_msu (s, a[j], yy[-j]); } s = L_shl (s, 3); *yy++ = round (s); move16 (); } for (i = 0; i < lg; i++) { y[i] = tmp[i + m]; move16 (); } /* Update of memory if update==1 */ test (); if (update != 0) { for (i = 0; i < m; i++) { mem[i] = y[lg - m + i]; move16 (); } } return; }