FreeCalypso > hg > gsm-codec-lib
view libtwamr/dec_lag6.c @ 473:2d46abdfbe91
libgsmefr version 1.1.0 for DHF addition
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Wed, 15 May 2024 05:22:02 +0000 |
parents | 7bea058d0640 |
children |
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/* ******************************************************************************** * * GSM AMR-NB speech codec R98 Version 7.6.0 December 12, 2001 * R99 Version 3.3.0 * REL-4 Version 4.1.0 * ******************************************************************************** * * File : dec_lag6.c * Purpose : Decoding of fractional pitch lag with 1/6 resolution. * ******************************************************************************** */ /* ******************************************************************************** * MODULE INCLUDE FILE AND VERSION ID ******************************************************************************** */ #include "namespace.h" #include "dec_lag6.h" /* ******************************************************************************** * INCLUDE FILES ******************************************************************************** */ #include "typedef.h" #include "basic_op.h" #include "no_count.h" /* ******************************************************************************** * PUBLIC PROGRAM CODE ******************************************************************************** */ /* ************************************************************************ * 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 (actually from previous frame) is used. * ************************************************************************ */ void Dec_lag6 ( 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 *T0, /* in/out: integer part of pitch lag */ Word16 *T0_frac /* output: fractional part of pitch lag */ ) { Word16 i; Word16 T0_min, T0_max; test (); if (i_subfr == 0) /* if 1st or 3rd subframe */ { 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 /* second or fourth subframe */ { /* find T0_min and T0_max for 2nd (or 4th) subframe */ T0_min = sub (*T0, 5); test (); if (sub (T0_min, pit_min) < 0) { T0_min = pit_min; move16 (); } T0_max = add (T0_min, 9); test (); if (sub (T0_max, pit_max) > 0) { T0_max = pit_max; move16 (); T0_min = sub (T0_max, 9); } /* 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)); move16 (); } }