80 lines
2.1 KiB
C
80 lines
2.1 KiB
C
/*
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ITU-T G.729A Speech Coder ANSI-C Source Code
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Version 1.1 Last modified: September 1996
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Copyright (c) 1996,
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AT&T, France Telecom, NTT, Universite de Sherbrooke
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All rights reserved.
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*/
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/*------------------------------------------------------------------------*
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* Function Dec_lag3 *
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* ~~~~~~~~ *
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* Decoding of fractional pitch lag with 1/3 resolution. *
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* See "Enc_lag3.c" for more details about the encoding procedure. *
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*------------------------------------------------------------------------*/
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#include "typedef.h"
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#include "basic_op.h"
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#include "ld8a.h"
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void
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Dec_lag3 (Word16 index, /* input : received pitch index */
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Word16 pit_min, /* input : minimum pitch lag */
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Word16 pit_max, /* input : maximum pitch lag */
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Word16 i_subfr, /* input : subframe flag */
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Word16 * T0, /* output: integer part of pitch lag */
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Word16 * T0_frac /* output: fractional part of pitch lag */
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)
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{
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Word16 i;
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Word16 T0_min, T0_max;
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if (i_subfr == 0) { /* if 1st subframe */
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if (sub (index, 197) < 0) {
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/* *T0 = (index+2)/3 + 19 */
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*T0 = add (mult (add (index, 2), 10923), 19);
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/* *T0_frac = index - *T0*3 + 58 */
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i = add (add (*T0, *T0), *T0);
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*T0_frac = add (sub (index, i), 58);
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}
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else {
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*T0 = sub (index, 112);
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*T0_frac = 0;
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}
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}
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else { /* second subframe */
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/* find T0_min and T0_max for 2nd subframe */
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T0_min = sub (*T0, 5);
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if (sub (T0_min, pit_min) < 0) {
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T0_min = pit_min;
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}
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T0_max = add (T0_min, 9);
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if (sub (T0_max, pit_max) > 0) {
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T0_max = pit_max;
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T0_min = sub (T0_max, 9);
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}
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/* i = (index+2)/3 - 1 */
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/* *T0 = i + t0_min; */
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i = sub (mult (add (index, 2), 10923), 1);
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*T0 = add (i, T0_min);
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/* t0_frac = index - 2 - i*3; */
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i = add (add (i, i), i);
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*T0_frac = sub (sub (index, 2), i);
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}
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return;
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}
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