FreeCalypso > hg > gsm-codec-lib
view libgsmefr/lsp_az.c @ 355:9beb01439a90
libtwamr: implement DHF check function
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Sun, 05 May 2024 21:59:18 +0000 |
parents | 5bc228bb421e |
children |
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/************************************************************************* * * FUNCTION: Lsp_Az * * PURPOSE: Converts from the line spectral pairs (LSP) to * LP coefficients, for a 10th order filter. * * DESCRIPTION: * - Find the coefficients of F1(z) and F2(z) (see Get_lsp_pol) * - Multiply F1(z) by 1+z^{-1} and F2(z) by 1-z^{-1} * - A(z) = ( F1(z) + F2(z) ) / 2 * *************************************************************************/ #include "gsm_efr.h" #include "typedef.h" #include "namespace.h" #include "basic_op.h" #include "oper_32b.h" #include "no_count.h" #include "sig_proc.h" /* local function */ static void Get_lsp_pol (Word16 *lsp, Word32 *f); void Lsp_Az ( Word16 lsp[], /* (i) : line spectral frequencies */ Word16 a[] /* (o) : predictor coefficients (order = 10) */ ) { Word16 i, j; Word32 f1[6], f2[6]; Word32 t0; Get_lsp_pol (&lsp[0], f1); Get_lsp_pol (&lsp[1], f2); for (i = 5; i > 0; i--) { f1[i] = L_add (f1[i], f1[i - 1]); move32 (); /* f1[i] += f1[i-1]; */ f2[i] = L_sub (f2[i], f2[i - 1]); move32 (); /* f2[i] -= f2[i-1]; */ } a[0] = 4096; move16 (); for (i = 1, j = 10; i <= 5; i++, j--) { t0 = L_add (f1[i], f2[i]); /* f1[i] + f2[i] */ a[i] = extract_l (L_shr_r (t0, 13)); move16 (); t0 = L_sub (f1[i], f2[i]); /* f1[i] - f2[i] */ a[j] = extract_l (L_shr_r (t0, 13)); move16 (); } return; } /************************************************************************* * * FUNCTION: Get_lsp_pol * * PURPOSE: Find the polynomial F1(z) or F2(z) from the LSPs. * If the LSP vector is passed at address 0 F1(z) is computed * and if it is passed at address 1 F2(z) is computed. * * DESCRIPTION: * This is performed by expanding the product polynomials: * * F1(z) = product ( 1 - 2 lsp[i] z^-1 + z^-2 ) * i=0,2,4,6,8 * F2(z) = product ( 1 - 2 lsp[i] z^-1 + z^-2 ) * i=1,3,5,7,9 * * where lsp[] is the LSP vector in the cosine domain. * * The expansion is performed using the following recursion: * * f[0] = 1 * b = -2.0 * lsp[0] * f[1] = b * for i=2 to 5 do * b = -2.0 * lsp[2*i-2]; * f[i] = b*f[i-1] + 2.0*f[i-2]; * for j=i-1 down to 2 do * f[j] = f[j] + b*f[j-1] + f[j-2]; * f[1] = f[1] + b; * *************************************************************************/ static void Get_lsp_pol (Word16 *lsp, Word32 *f) { Word16 i, j, hi, lo; Word32 t0; /* f[0] = 1.0; */ *f = L_mult (4096, 2048); move32 (); f++; move32 (); *f = L_msu ((Word32) 0, *lsp, 512); /* f[1] = -2.0 * lsp[0]; */ f++; move32 (); lsp += 2; /* Advance lsp pointer */ for (i = 2; i <= 5; i++) { *f = f[-2]; move32 (); for (j = 1; j < i; j++, f--) { L_Extract (f[-1], &hi, &lo); t0 = Mpy_32_16 (hi, lo, *lsp); /* t0 = f[-1] * lsp */ t0 = L_shl (t0, 1); *f = L_add (*f, f[-2]); move32 (); /* *f += f[-2] */ *f = L_sub (*f, t0);move32 (); /* *f -= t0 */ } *f = L_msu (*f, *lsp, 512); move32 (); /* *f -= lsp<<9 */ f += i; /* Advance f pointer */ lsp += 2; /* Advance lsp pointer */ } return; }