FreeCalypso > hg > gsm-codec-lib
view libgsmfr2/long_term.c @ 449:2af2b5c12268
Library-versions: libtwamr is officially version 1.0.0
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Fri, 10 May 2024 01:43:05 +0000 |
parents | 65d3304502bd |
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/* * This C source file has been adapted from TU-Berlin libgsm source, * original notice follows: * * Copyright 1992 by Jutta Degener and Carsten Bormann, Technische * Universitaet Berlin. See the accompanying file "COPYRIGHT" for * details. THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE. */ #include <stdint.h> #include <assert.h> #include "tw_gsmfr.h" #include "typedef.h" #include "ed_state.h" #include "ed_internal.h" /* * 4.2.11 .. 4.2.12 LONG TERM PREDICTOR (LTP) SECTION */ /* * This module computes the LTP gain (bc) and the LTP lag (Nc) * for the long term analysis filter. This is done by calculating a * maximum of the cross-correlation function between the current * sub-segment short term residual signal d[0..39] (output of * the short term analysis filter; for simplification the index * of this array begins at 0 and ends at 39 for each sub-segment of the * RPE-LTP analysis) and the previous reconstructed short term * residual signal dp[ -120 .. -1 ]. A dynamic scaling must be * performed to avoid overflow. */ static void Calculation_of_the_LTP_parameters ( register word * d, /* [0..39] IN */ register word * dp, /* [-120..-1] IN */ word * bc_out, /* OUT */ word * Nc_out /* OUT */ ) { register int k, lambda; word Nc, bc; word wt[40]; longword L_max, L_power; word R, S, dmax, scal; register word temp; /* Search of the optimum scaling of d[0..39]. */ dmax = 0; for (k = 0; k <= 39; k++) { temp = d[k]; temp = GSM_ABS( temp ); if (temp > dmax) dmax = temp; } temp = 0; if (dmax == 0) scal = 0; else { assert(dmax > 0); temp = gsm_norm( (longword)dmax << 16 ); } if (temp > 6) scal = 0; else scal = 6 - temp; assert(scal >= 0); /* Initialization of a working array wt */ for (k = 0; k <= 39; k++) wt[k] = SASR( d[k], scal ); /* Search for the maximum cross-correlation and coding of the LTP lag */ L_max = 0; Nc = 40; /* index for the maximum cross-correlation */ for (lambda = 40; lambda <= 120; lambda++) { # undef STEP # define STEP(k) (longword)wt[k] * dp[k - lambda] register longword L_result; L_result = STEP(0) ; L_result += STEP(1) ; L_result += STEP(2) ; L_result += STEP(3) ; L_result += STEP(4) ; L_result += STEP(5) ; L_result += STEP(6) ; L_result += STEP(7) ; L_result += STEP(8) ; L_result += STEP(9) ; L_result += STEP(10) ; L_result += STEP(11) ; L_result += STEP(12) ; L_result += STEP(13) ; L_result += STEP(14) ; L_result += STEP(15) ; L_result += STEP(16) ; L_result += STEP(17) ; L_result += STEP(18) ; L_result += STEP(19) ; L_result += STEP(20) ; L_result += STEP(21) ; L_result += STEP(22) ; L_result += STEP(23) ; L_result += STEP(24) ; L_result += STEP(25) ; L_result += STEP(26) ; L_result += STEP(27) ; L_result += STEP(28) ; L_result += STEP(29) ; L_result += STEP(30) ; L_result += STEP(31) ; L_result += STEP(32) ; L_result += STEP(33) ; L_result += STEP(34) ; L_result += STEP(35) ; L_result += STEP(36) ; L_result += STEP(37) ; L_result += STEP(38) ; L_result += STEP(39) ; if (L_result > L_max) { Nc = lambda; L_max = L_result; } } *Nc_out = Nc; L_max <<= 1; /* Rescaling of L_max */ assert(scal <= 100 && scal >= -100); L_max = L_max >> (6 - scal); /* sub(6, scal) */ assert( Nc <= 120 && Nc >= 40); /* Compute the power of the reconstructed short term residual * signal dp[..] */ L_power = 0; for (k = 0; k <= 39; k++) { register longword L_temp; L_temp = SASR( dp[k - Nc], 3 ); L_power += L_temp * L_temp; } L_power <<= 1; /* from L_MULT */ /* Normalization of L_max and L_power */ if (L_max <= 0) { *bc_out = 0; return; } if (L_max >= L_power) { *bc_out = 3; return; } temp = gsm_norm( L_power ); R = SASR( L_max << temp, 16 ); S = SASR( L_power << temp, 16 ); /* Coding of the LTP gain */ /* Table 4.3a must be used to obtain the level DLB[i] for the * quantization of the LTP gain b to get the coded version bc. */ for (bc = 0; bc <= 2; bc++) if (R <= gsm_mult(S, gsm_DLB[bc])) break; *bc_out = bc; } /* 4.2.12 */ static void Long_term_analysis_filtering ( word bc, /* IN */ word Nc, /* IN */ register word * dp, /* previous d [-120..-1] IN */ register word * d, /* d [0..39] IN */ register word * dpp, /* estimate [0..39] OUT */ register word * e /* long term res. signal [0..39] OUT */ ) /* * In this part, we have to decode the bc parameter to compute * the samples of the estimate dpp[0..39]. The decoding of bc needs the * use of table 4.3b. The long term residual signal e[0..39] * is then calculated to be fed to the RPE encoding section. */ { register int k; register longword ltmp; # undef STEP # define STEP(BP) \ for (k = 0; k <= 39; k++) { \ dpp[k] = GSM_MULT_R( BP, dp[k - Nc]); \ e[k] = GSM_SUB( d[k], dpp[k] ); \ } switch (bc) { case 0: STEP( 3277 ); break; case 1: STEP( 11469 ); break; case 2: STEP( 21299 ); break; case 3: STEP( 32767 ); break; } } void Gsm_Long_Term_Predictor ( /* 4x for 160 samples */ struct gsmfr_0610_state * S, word * d, /* [0..39] residual signal IN */ word * dp, /* [-120..-1] d' IN */ word * e, /* [0..39] OUT */ word * dpp, /* [0..39] OUT */ word * Nc, /* correlation lag OUT */ word * bc /* gain factor OUT */ ) { assert( d ); assert( dp ); assert( e ); assert( dpp); assert( Nc ); assert( bc ); Calculation_of_the_LTP_parameters(d, dp, bc, Nc); Long_term_analysis_filtering( *bc, *Nc, dp, d, dpp, e ); } /* 4.3.2 */ void Gsm_Long_Term_Synthesis_Filtering ( struct gsmfr_0610_state * S, word Ncr, word bcr, register word * erp, /* [0..39] IN */ register word * drp /* [-120..-1] IN, [-120..40] OUT */ ) /* * This procedure uses the bcr and Ncr parameter to realize the * long term synthesis filtering. The decoding of bcr needs * table 4.3b. */ { register longword ltmp; /* for ADD */ register int k; word brp, drpp, Nr; /* Check the limits of Nr. */ Nr = Ncr < 40 || Ncr > 120 ? S->nrp : Ncr; S->nrp = Nr; assert(Nr >= 40 && Nr <= 120); /* Decoding of the LTP gain bcr */ brp = gsm_QLB[ bcr ]; /* Computation of the reconstructed short term residual * signal drp[0..39] */ assert(brp != MIN_WORD); for (k = 0; k <= 39; k++) { drpp = GSM_MULT_R( brp, drp[ k - Nr ] ); drp[k] = GSM_ADD( erp[k], drpp ); } /* * Update of the reconstructed short term residual signal * drp[ -1..-120 ] */ for (k = 0; k <= 119; k++) drp[ -120 + k ] = drp[ -80 + k ]; }