FreeCalypso > hg > gsm-codec-lib
view libgsmefr/pstfilt2.c @ 296:e0d42e87da96
frtest: new utility gsmfr-decode-rb
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Sun, 14 Apr 2024 20:36:29 +0000 |
parents | 41d8e8f4058d |
children |
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/************************************************************************* * * FILE NAME: pstfilt2.c * * Performs adaptive postfiltering on the synthesis speech * * FUNCTIONS INCLUDED: Init_Post_Filter() and Post_Filter() * *************************************************************************/ #include "gsm_efr.h" #include "typedef.h" #include "namespace.h" #include "basic_op.h" #include "sig_proc.h" #include "memops.h" #include "no_count.h" #include "codec.h" #include "cnst.h" #include "dec_state.h" /*---------------------------------------------------------------* * Postfilter constant parameters (defined in "cnst.h") * *---------------------------------------------------------------* * L_FRAME : Frame size. * * L_SUBFR : Sub-frame size. * * M : LPC order. * * MP1 : LPC order+1 * * MU : Factor for tilt compensation filter * * AGC_FAC : Factor for automatic gain control * *---------------------------------------------------------------*/ #define L_H 22 /* size of truncated impulse response of A(z/g1)/A(z/g2) */ /*------------------------------------------------------------* * static vectors * *------------------------------------------------------------*/ /* Spectral expansion factors */ const Word16 F_gamma3[M] = { 22938, 16057, 11240, 7868, 5508, 3856, 2699, 1889, 1322, 925 }; const Word16 F_gamma4[M] = { 24576, 18432, 13824, 10368, 7776, 5832, 4374, 3281, 2461, 1846 }; /************************************************************************* * * FUNCTION: Init_Post_Filter * * PURPOSE: Initializes the postfilter parameters. * *************************************************************************/ void Init_Post_Filter (struct EFR_decoder_state *st) { Set_zero (st->mem_syn_pst, M); Set_zero (st->res2, L_SUBFR); return; } /************************************************************************* * FUNCTION: Post_Filter() * * PURPOSE: postfiltering of synthesis speech. * * DESCRIPTION: * The postfiltering process is described as follows: * * - inverse filtering of syn[] through A(z/0.7) to get res2[] * - tilt compensation filtering; 1 - MU*k*z^-1 * - synthesis filtering through 1/A(z/0.75) * - adaptive gain control * *************************************************************************/ void Post_Filter ( struct EFR_decoder_state *st, Word16 *syn, /* in/out: synthesis speech (postfiltered is output) */ Word16 *Az_4 /* input: interpolated LPC parameters in all subframes */ ) { /*-------------------------------------------------------------------* * Declaration of parameters * *-------------------------------------------------------------------*/ Word16 syn_pst[L_FRAME]; /* post filtered synthesis speech */ Word16 Ap3[MP1], Ap4[MP1]; /* bandwidth expanded LP parameters */ Word16 *Az; /* pointer to Az_4: */ /* LPC parameters in each subframe */ Word16 i_subfr; /* index for beginning of subframe */ Word16 h[L_H]; Word16 i; Word16 temp1, temp2; Word32 L_tmp; /*-----------------------------------------------------* * Post filtering * *-----------------------------------------------------*/ Az = Az_4; for (i_subfr = 0; i_subfr < L_FRAME; i_subfr += L_SUBFR) { /* Find weighted filter coefficients Ap3[] and ap[4] */ Weight_Ai (Az, F_gamma3, Ap3); Weight_Ai (Az, F_gamma4, Ap4); /* filtering of synthesis speech by A(z/0.7) to find res2[] */ Residu (Ap3, &syn[i_subfr], st->res2, L_SUBFR); /* tilt compensation filter */ /* impulse response of A(z/0.7)/A(z/0.75) */ Copy (Ap3, h, M + 1); Set_zero (&h[M + 1], L_H - M - 1); Syn_filt (Ap4, h, h, L_H, &h[M + 1], 0); /* 1st correlation of h[] */ L_tmp = L_mult (h[0], h[0]); for (i = 1; i < L_H; i++) { L_tmp = L_mac (L_tmp, h[i], h[i]); } temp1 = extract_h (L_tmp); L_tmp = L_mult (h[0], h[1]); for (i = 1; i < L_H - 1; i++) { L_tmp = L_mac (L_tmp, h[i], h[i + 1]); } temp2 = extract_h (L_tmp); test (); if (temp2 <= 0) { temp2 = 0; move16 (); } else { temp2 = mult (temp2, MU); temp2 = div_s (temp2, temp1); } preemphasis (st, st->res2, temp2, L_SUBFR); /* filtering through 1/A(z/0.75) */ Syn_filt (Ap4, st->res2, &syn_pst[i_subfr], L_SUBFR, st->mem_syn_pst, 1); /* scale output to input */ agc (st, &syn[i_subfr], &syn_pst[i_subfr], AGC_FAC, L_SUBFR); Az += MP1; } /* update syn[] buffer */ Copy (&syn[L_FRAME - M], &syn[-M], M); /* overwrite synthesis speech by postfiltered synthesis speech */ Copy (syn_pst, syn, L_FRAME); return; }