FreeCalypso > hg > gsm-codec-lib
view libgsmefr/autocorr.c @ 285:cfa3006a66da
gsmfr-decode-r: convert to libgsmfr2
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Sun, 14 Apr 2024 06:04:32 +0000 |
parents | 92dc7f0082a3 |
children |
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/************************************************************************* * * FUNCTION: autocorr * * PURPOSE: Compute autocorrelations of signal with windowing * * DESCRIPTION: * - Windowing of input speech: s'[n] = s[n] * w[n] * - Autocorrelations of input speech: * r[k] = sum_{i=k}^{239} s'[i]*s'[i-k] k=0,...,10 * The autocorrelations are expressed in normalized double precision * format. * *************************************************************************/ #include "gsm_efr.h" #include "typedef.h" #include "namespace.h" #include "basic_op.h" #include "oper_32b.h" #include "no_count.h" #include "cnst.h" #include "sig_proc.h" Word16 Autocorr ( Word16 x[], /* (i) : Input signal */ Word16 m, /* (i) : LPC order */ Word16 r_h[], /* (o) : Autocorrelations (msb) */ Word16 r_l[], /* (o) : Autocorrelations (lsb) */ const Word16 wind[] /* (i) : window for LPC analysis */ ) { Word16 i, j, norm; Word16 y[L_WINDOW]; Word32 sum; Word16 overfl, overfl_shft; /* Windowing of signal */ for (i = 0; i < L_WINDOW; i++) { y[i] = mult_r (x[i], wind[i]); move16 (); } /* Compute r[0] and test for overflow */ overfl_shft = 0; move16 (); do { overfl = 0; move16 (); sum = 0L; move32 (); for (i = 0; i < L_WINDOW; i++) { sum = L_mac (sum, y[i], y[i]); } /* If overflow divide y[] by 4 */ test (); if (L_sub (sum, MAX_32) == 0L) { overfl_shft = add (overfl_shft, 4); overfl = 1; move16 (); /* Set the overflow flag */ for (i = 0; i < L_WINDOW; i++) { y[i] = shr (y[i], 2); move16 (); } } test (); } while (overfl != 0); sum = L_add (sum, 1L); /* Avoid the case of all zeros */ /* Normalization of r[0] */ norm = norm_l (sum); sum = L_shl (sum, norm); L_Extract (sum, &r_h[0], &r_l[0]); /* Put in DPF format (see oper_32b) */ /* r[1] to r[m] */ for (i = 1; i <= m; i++) { sum = 0; move32 (); for (j = 0; j < L_WINDOW - i; j++) { sum = L_mac (sum, y[j], y[j + i]); } sum = L_shl (sum, norm); L_Extract (sum, &r_h[i], &r_l[i]); } norm = sub (norm, overfl_shft); return norm; }