FreeCalypso > hg > gsm-codec-lib
view libtwamr/enc_lag6.c @ 382:693ea1d5cf1e
libtwamr: integrate int_lsf.c
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Mon, 06 May 2024 05:45:31 +0000 |
parents | 0349de7c45b7 |
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 : enc_lag6.c * Purpose : Encoding of fractional pitch lag with 1/6 resolution. * ******************************************************************************** */ /* ******************************************************************************** * MODULE INCLUDE FILE AND VERSION ID ******************************************************************************** */ #include "namespace.h" #include "enc_lag6.h" /* ******************************************************************************** * INCLUDE FILES ******************************************************************************** */ #include "typedef.h" #include "basic_op.h" #include "no_count.h" /* ******************************************************************************** * LOCAL VARIABLES AND TABLES ******************************************************************************** */ /* ******************************************************************************** * PUBLIC PROGRAM CODE ******************************************************************************** */ /************************************************************************* * * FUNCTION: Enc_lag6 * * PURPOSE: Encoding of fractional pitch lag with 1/6 resolution. * * DESCRIPTION: * First and third subframes: * -------------------------- * The pitch range is divided as follows: * 17 3/6 to 94 3/6 resolution 1/6 * 95 to 143 resolution 1 * * The period is encoded with 9 bits. * For the range with fractions: * index = (T-17)*6 + frac - 3; * where T=[17..94] and frac=[-2,-1,0,1,2,3] * and for the integer only range * index = (T - 95) + 463; where T=[95..143] * * Second and fourth subframes: * ---------------------------- * For the 2nd and 4th subframes a resolution of 1/6 is always used, * and the search range is relative to the lag in previous subframe. * If t0 is the lag in the previous subframe then * t_min=t0-5 and t_max=t0+4 and the range is given by * (t_min-1) 3/6 to (t_max) 3/6 * * The period in the 2nd (and 4th) subframe is encoded with 6 bits: * index = (T-(t_min-1))*6 + frac - 3; * where T=[t_min-1..t_max] and frac=[-2,-1,0,1,2,3] * * Note that 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 and the pitch from previous subframe should be used. * *************************************************************************/ Word16 Enc_lag6 ( /* o : Return index of encoding */ Word16 T0, /* i : Pitch delay */ Word16 T0_frac, /* i : Fractional pitch delay */ Word16 T0_min, /* i : minimum of search range */ Word16 delta_flag /* i : Flag for 1st (or 3rd) subframe */ ) { Word16 index, i; test (); if (delta_flag == 0) /* if 1st or 3rd subframe */ { /* encode pitch delay (with fraction) */ test (); if (sub (T0, 94) <= 0) { /* index = T0*6 - 105 + T0_frac */ i = add (add (T0, T0), T0); index = add (sub (add (i, i), 105), T0_frac); } else { index = add (T0, 368); } } else /* if second or fourth subframe */ { /* index = 6*(T0-T0_min) + 3 + T0_frac */ i = sub (T0, T0_min); i = add (add (i, i), i); index = add (add (add (i, i), 3), T0_frac); } return index; }