FreeCalypso > hg > gsm-codec-lib
view libgsmefr/agc.c @ 467:ad032051166a
doc: AMR-EFR-hybrid-emu new article
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Sun, 12 May 2024 23:54:43 +0000 |
parents | 7b11cbe99a0e |
children |
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/************************************************************************* * * FUNCTION: agc * * PURPOSE: Scales the postfilter output on a subframe basis by automatic * control of the subframe gain. * * DESCRIPTION: * sig_out[n] = sig_out[n] * gain[n]; * where gain[n] is the gain at the nth sample given by * gain[n] = agc_fac * gain[n-1] + (1 - agc_fac) g_in/g_out * g_in/g_out is the square root of the ratio of energy at the input * and output of the postfilter. * *************************************************************************/ #include "gsm_efr.h" #include "typedef.h" #include "namespace.h" #include "basic_op.h" #include "no_count.h" #include "cnst.h" #include "dec_state.h" #include "sig_proc.h" void agc ( struct EFR_decoder_state *st, Word16 *sig_in, /* (i) : postfilter input signal */ Word16 *sig_out, /* (i/o) : postfilter output signal */ Word16 agc_fac, /* (i) : AGC factor */ Word16 l_trm /* (i) : subframe size */ ) { Word16 i, exp; Word16 gain_in, gain_out, g0, gain; Word32 s; Word16 temp; /* calculate gain_out with exponent */ temp = shr (sig_out[0], 2); s = L_mult (temp, temp); for (i = 1; i < l_trm; i++) { temp = shr (sig_out[i], 2); s = L_mac (s, temp, temp); } if (s == 0) { st->past_gain = 0; return; } exp = sub (norm_l (s), 1); gain_out = round (L_shl (s, exp)); /* calculate gain_in with exponent */ temp = shr (sig_in[0], 2); s = L_mult (temp, temp); for (i = 1; i < l_trm; i++) { temp = shr (sig_in[i], 2); s = L_mac (s, temp, temp); } if (s == 0) { g0 = 0; } else { i = norm_l (s); gain_in = round (L_shl (s, i)); exp = sub (exp, i); /*---------------------------------------------------* * g0 = (1-agc_fac) * sqrt(gain_in/gain_out); * *---------------------------------------------------*/ s = L_deposit_l (div_s (gain_out, gain_in)); s = L_shl (s, 7); /* s = gain_out / gain_in */ s = L_shr (s, exp); /* add exponent */ s = Inv_sqrt (s); i = round (L_shl (s, 9)); /* g0 = i * (1-agc_fac) */ g0 = mult (i, sub (32767, agc_fac)); } /* compute gain[n] = agc_fac * gain[n-1] + (1-agc_fac) * sqrt(gain_in/gain_out) */ /* sig_out[n] = gain[n] * sig_out[n] */ gain = st->past_gain; for (i = 0; i < l_trm; i++) { gain = mult (gain, agc_fac); gain = add (gain, g0); sig_out[i] = extract_h (L_shl (L_mult (sig_out[i], gain), 3)); } st->past_gain = gain; return; } void agc2 ( Word16 *sig_in, /* (i) : postfilter input signal */ Word16 *sig_out, /* (i/o) : postfilter output signal */ Word16 l_trm /* (i) : subframe size */ ) { Word16 i, exp; Word16 gain_in, gain_out, g0; Word32 s; Word16 temp; /* calculate gain_out with exponent */ temp = shr (sig_out[0], 2); s = L_mult (temp, temp); for (i = 1; i < l_trm; i++) { temp = shr (sig_out[i], 2); s = L_mac (s, temp, temp); } test (); if (s == 0) { return; } exp = sub (norm_l (s), 1); gain_out = round (L_shl (s, exp)); /* calculate gain_in with exponent */ temp = shr (sig_in[0], 2); s = L_mult (temp, temp); for (i = 1; i < l_trm; i++) { temp = shr (sig_in[i], 2); s = L_mac (s, temp, temp); } test (); if (s == 0) { g0 = 0; move16 (); } else { i = norm_l (s); gain_in = round (L_shl (s, i)); exp = sub (exp, i); /*---------------------------------------------------* * g0 = sqrt(gain_in/gain_out); * *---------------------------------------------------*/ s = L_deposit_l (div_s (gain_out, gain_in)); s = L_shl (s, 7); /* s = gain_out / gain_in */ s = L_shr (s, exp); /* add exponent */ s = Inv_sqrt (s); g0 = round (L_shl (s, 9)); } /* sig_out(n) = gain(n) sig_out(n) */ for (i = 0; i < l_trm; i++) { sig_out[i] = extract_h (L_shl (L_mult (sig_out[i], g0), 3)); move16 (); } return; }