FreeCalypso > hg > gsm-codec-lib
view libgsmefr/lsp_lsf.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> |
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date | Tue, 03 Jan 2023 00:12:18 +0000 |
parents | 8d3412b7ec4e |
children | bcd337afa0f1 |
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/************************************************************************* * * FUNCTIONS: Lsp_lsf and Lsf_lsp * * PURPOSE: * Lsp_lsf: Transformation lsp to lsf * Lsf_lsp: Transformation lsf to lsp * * DESCRIPTION: * lsp[i] = cos(2*pi*lsf[i]) and lsf[i] = arccos(lsp[i])/(2*pi) * * The transformation from lsp[i] to lsf[i] and lsf[i] to lsp[i] are * approximated by a look-up table and interpolation. * *************************************************************************/ #include "gsm_efr.h" #include "typedef.h" #include "namespace.h" #include "basic_op.h" #include "no_count.h" #include "sig_proc.h" #include "lsp_lsf.tab" /* Look-up table for transformations */ void Lsf_lsp ( Word16 lsf[], /* (i) : lsf[m] normalized (range: 0.0<=val<=0.5) */ Word16 lsp[], /* (o) : lsp[m] (range: -1<=val<1) */ Word16 m /* (i) : LPC order */ ) { Word16 i, ind, offset; Word32 L_tmp; for (i = 0; i < m; i++) { ind = shr (lsf[i], 8); /* ind = b8-b15 of lsf[i] */ offset = lsf[i] & 0x00ff; logic16 (); /* offset = b0-b7 of lsf[i] */ /* lsp[i] = table[ind]+ ((table[ind+1]-table[ind])*offset) / 256 */ L_tmp = L_mult (sub (table[ind + 1], table[ind]), offset); lsp[i] = add (table[ind], extract_l (L_shr (L_tmp, 9))); move16 (); } return; } void Lsp_lsf ( Word16 lsp[], /* (i) : lsp[m] (range: -1<=val<1) */ Word16 lsf[], /* (o) : lsf[m] normalized (range: 0.0<=val<=0.5) */ Word16 m /* (i) : LPC order */ ) { Word16 i, ind; Word32 L_tmp; ind = 63; /* begin at end of table -1 */ for (i = m - 1; i >= 0; i--) { /* find value in table that is just greater than lsp[i] */ test (); while (sub (table[ind], lsp[i]) < 0) { ind--; test (); } /* acos(lsp[i])= ind*256 + ( ( lsp[i]-table[ind] ) * slope[ind] )/4096 */ L_tmp = L_mult (sub (lsp[i], table[ind]), slope[ind]); /*(lsp[i]-table[ind])*slope[ind])>>12*/ lsf[i] = round (L_shl (L_tmp, 3)); move16 (); lsf[i] = add (lsf[i], shl (ind, 8)); move16 (); } return; }