FreeCalypso > hg > gsm-codec-lib
view libgsmefr/autocorr.c @ 183:452c1d5a6268
libgsmefr BFI w/o data: emit zero output after decoder reset
In real-life usage, each EFR decoder session will most likely begin
with lots of BFI frames before the first real frame arrives. However,
because the spec-defined home state of the decoder is speech rather
than CN, our regular logic for BFI w/o data would have to feed
pseudorandom noise to the decoder (in the "fixed codebook excitation
pulses" part), which is silly to do at the beginning of the decoder
session right out of reset. Therefore, let's check reset_flag_old,
and if we are still in the reset state, simply emit zero output.
author | Mychaela Falconia <falcon@freecalypso.org> |
---|---|
date | Tue, 03 Jan 2023 00:12:18 +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; }