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