FreeCalypso > hg > gsm-codec-lib
view libgsmefr/dec_lag6.c @ 146:0fa0cd251a31
gsmefr-dec-parse: use factored-out ETSI bit reader
author | Mychaela Falconia <falcon@freecalypso.org> |
---|---|
date | Wed, 14 Dec 2022 08:05:08 +0000 |
parents | cb080ec1817e |
children | f387ee919f2c |
line wrap: on
line source
/************************************************************************* * FUNCTION: Dec_lag6 * * PURPOSE: Decoding of fractional pitch lag with 1/6 resolution. * Extract the integer and fraction parts of the pitch lag from * the received adaptive codebook index. * * See "Enc_lag6.c" for more details about the encoding procedure. * * The fractional lag in 1st and 3rd subframes is encoded with 9 bits * while that in 2nd and 4th subframes is relatively encoded with 6 bits. * Note that in relative encoding only 61 values are used. If the * decoder receives 61, 62, or 63 as the relative pitch index, it means * that a transmission error occurred. In this case, the pitch lag from * previous subframe is used. * *************************************************************************/ #include "gsm_efr.h" #include "typedef.h" #include "namespace.h" #include "basic_op.h" #include "no_count.h" #include "codec.h" #include "cnst.h" #include "dec_state.h" Word16 Dec_lag6 ( /* output: return integer pitch lag */ struct EFR_decoder_state *st, Word16 index, /* input : received pitch index */ Word16 pit_min, /* input : minimum pitch lag */ Word16 pit_max, /* input : maximum pitch lag */ Word16 i_subfr, /* input : subframe flag */ Word16 L_frame_by2,/* input : speech frame size divided by 2 */ Word16 *T0_frac, /* output: fractional part of pitch lag */ Word16 bfi, /* input : bad frame indicator */ Word16 *T0_min, Word16 *T0_max ) { Word16 pit_flag; Word16 T0, i; pit_flag = i_subfr; move16 (); /* flag for 1st or 3rd subframe */ test (); if (sub (i_subfr, L_frame_by2) == 0) { pit_flag = 0; move16 (); } test (); if (pit_flag == 0) /* if 1st or 3rd subframe */ { test (); if (bfi == 0) { /* if bfi == 0 decode pitch */ test (); if (sub (index, 463) < 0) { /* T0 = (index+5)/6 + 17 */ T0 = add (mult (add (index, 5), 5462), 17); i = add (add (T0, T0), T0); /* *T0_frac = index - T0*6 + 105 */ *T0_frac = add (sub (index, add (i, i)), 105); move16 (); } else { T0 = sub (index, 368); *T0_frac = 0; move16 (); } } else /* bfi == 1 */ { T0 = st->old_T0; *T0_frac = 0; } /* find T0_min and T0_max for 2nd (or 4th) subframe */ *T0_min = sub (T0, 5); if (sub (*T0_min, pit_min) < 0) { *T0_min = pit_min; } *T0_max = add (*T0_min, 9); if (sub (*T0_max, pit_max) > 0) { *T0_max = pit_max; *T0_min = sub (*T0_max, 9); } } else /* second or fourth subframe */ { test (); test (); /* if bfi == 0 decode pitch */ if ((bfi == 0) && (sub (index, 61) < 0)) { /* i = (index+5)/6 - 1 */ i = sub (mult (add (index, 5), 5462), 1); T0 = add (i, *T0_min); i = add (add (i, i), i); *T0_frac = sub (sub (index, 3), add (i, i)); } else /* bfi == 1 OR index >= 61 */ { T0 = st->old_T0; *T0_frac = 0; } } st->old_T0 = T0; return T0; }