FreeCalypso > hg > gsm-codec-lib
view libgsmefr/agc.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 | 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; }