ref: 012ae34cae3f152370a7c58602d8cbb841cd8aad
dir: /amr-wb/d2t64fx.c/
/*-------------------------------------------------------------------*
* D2T64FX.C *
*-------------------------------------------------------------------*
* 12 bits algebraic codebook decoder. *
* 2 tracks x 32 positions per track = 64 samples. *
* *
* 12 bits --> 2 pulses in a frame of 64 samples. *
* *
* All pulses can have two (2) possible amplitudes: +1 or -1. *
* Each pulse can have 32 possible positions. *
* *
* See dec2t64.c for more details of the algebraic code. *
*-------------------------------------------------------------------*/
#include "typedef.h"
#include "basic_op.h"
#include "count.h"
#include "cnst.h"
#define L_CODE 64 /* codevector length */
#define NB_TRACK 2 /* number of track */
#define NB_POS 32 /* number of position */
void DEC_ACELP_2t64_fx(
Word16 index, /* (i) : 12 bits index */
Word16 code[] /* (o) :Q9 algebraic (fixed) codebook excitation */
)
{
Word16 i, i0, i1;
for (i = 0; i < L_CODE; i++)
{
code[i] = 0; move16();
}
/* decode the positions and signs of pulses and build the codeword */
i0 = (Word16) (shr(index, 5) & 0x003E);logic16();
i1 = (Word16) (add(shl((Word16) (index & 0x001F), 1), 1)); logic16();
test();logic16();
if ((shr(index, 6) & NB_POS) == 0)
code[i0] = 512;
else
code[i0] = -512;
test();logic16();
if ((index & NB_POS) == 0)
code[i1] = 512;
else
code[i1] = -512;
return;
}