FreeCalypso > hg > gsm-codec-lib
view libtwamr/dec_lag3.c @ 458:e26b974f7ba3
doc/AMR-study-utils: update for the current situation
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Fri, 10 May 2024 18:45:36 +0000 |
parents | fb001496ca8c |
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_lag3.c * Purpose : Decoding of fractional pitch lag with 1/3 resolution. * Extract the integer and fraction parts of the pitch lag from * the received adaptive codebook index. * ******************************************************************************** */ /* ******************************************************************************** * MODULE INCLUDE FILE AND VERSION ID ******************************************************************************** */ #include "namespace.h" #include "dec_lag3.h" /* ******************************************************************************** * INCLUDE FILES ******************************************************************************** */ #include "typedef.h" #include "basic_op.h" #include "no_count.h" /* ******************************************************************************** * LOCAL VARIABLES AND TABLES ******************************************************************************** */ /* ******************************************************************************** * PUBLIC PROGRAM CODE ******************************************************************************** */ /************************************************************************* * FUNCTION: Dec_lag3 * * PURPOSE: Decoding of fractional pitch lag with 1/3 resolution. * Extract the integer and fraction parts of the pitch lag from * the received adaptive codebook index. * * See "Enc_lag3.c" for more details about the encoding procedure. * * The fractional lag in 1st and 3rd subframes is encoded with 8 bits * while that in 2nd and 4th subframes is relatively encoded with 4, 5 * and 6 bits depending on the mode. * *************************************************************************/ void Dec_lag3(Word16 index, /* i : received pitch index */ Word16 t0_min, /* i : minimum of search range */ Word16 t0_max, /* i : maximum of search range */ Word16 i_subfr, /* i : subframe flag */ Word16 T0_prev, /* i : integer pitch delay of last subframe used in 2nd and 4th subframes */ Word16 * T0, /* o : integer part of pitch lag */ Word16 * T0_frac, /* o : fractional part of pitch lag */ Word16 flag4 /* i : flag for encoding with 4 bits */ ) { Word16 i; Word16 tmp_lag; test (); if (i_subfr == 0) { /* if 1st or 3rd subframe */ test (); if (sub(index, 197) < 0) { *T0 = add(mult(add(index, 2), 10923), 19); i = add(add(*T0, *T0), *T0); *T0_frac = add(sub(index, i), 58); } else { *T0 = sub(index, 112); *T0_frac = 0; move16 (); } } else { /* 2nd or 4th subframe */ test (); if (flag4 == 0) { /* 'normal' decoding: either with 5 or 6 bit resolution */ i = sub(mult(add(index, 2), 10923), 1); *T0 = add(i, t0_min); i = add(add(i, i), i); *T0_frac = sub(sub(index, 2), i); } else { /* decoding with 4 bit resolution */ tmp_lag = T0_prev; move16 (); test (); if ( sub( sub(tmp_lag, t0_min), 5) > 0) tmp_lag = add (t0_min, 5); test (); if ( sub( sub(t0_max, tmp_lag), 4) > 0) tmp_lag = sub (t0_max, 4); test (); if (sub(index, 4) < 0) { i = sub(tmp_lag, 5); *T0 = add(i, index); *T0_frac = 0; move16 (); } else { test (); if (sub(index, 12) < 0) { i = sub(mult(sub(index, 5), 10923), 1); *T0 = add(i, tmp_lag); i = add(add(i, i), i); *T0_frac = sub(sub(index, 9), i); } else { i = add( sub (index, 12), tmp_lag); *T0 = add (i, 1); *T0_frac = 0; move16 (); } } } /* end if (decoding with 4 bit resolution) */ } return; }