www.pudn.com > lpc.zip > decode.c
/******************************************************************
*
* DECODE Version 52
*
******************************************************************
*
* This subroutine provides error correction and decoding
* for all LPC parameters
*
* INPUTS:
* ORDER - Number of RC's
* IPITV - Index value of pitch
* IRMS - Coded Energy
* IRC - Coded Reflection Coefficients
* CORRP - Error correction:
* If FALSE, parameters are decoded directly with no delay. If TRUE,
* most important parameter bits are protected by Hamming code and
* median smoothed. This requires an additional frame of delay.
* OUTPUTS:
* VOICE - Half frame voicing decisions
* PITCH - Decoded pitch
* RMS - Energy
* RC - Reflection coefficients
*
* NOTE: Zero RC's should be done more directly, but this would affect
* coded parameter printout.
*/
#include "config.ch"
#include "lpcdefs.h"
#include
/*int rmst[64]={1024,936,856,784,718,656,600,550,
502,460,420,384,352,328,294,270,
246,226,206,188,172,158,144,132,
120,110,102,92,84,78,70,64,
60,54,50,46,42,38,34,32,
30,26,24,22,20,18,17,16,
15,14,13,12,11,10,9,8,
7,6,5,4,3,2,1,0};
**** -- this is defined in encode.c also */
extern int rmst[64];
int ivtab[32] ={
24960,24960,24960,24960, 25480,25480, 25483, 25480,
16640, 1560,1560,1560, 16640, 1816, 1563,
1560, 24960,24960, 24859, 24856, 26001,
25881, 25915, 25913, 1560,1560, 7800,
3640, 1561,1561, 3643, 3641
};
float corth[4][8]={
32767.,32767.,32.,32.,32.,32.,16.,16.,
10.,8.,6.4,6.4,11.2,11.2,5.6,5.6,
5.,4.,3.2,3.2,6.4,6.4,3.2,3.2,
0., 0.,0.,0.,0.,0.,0.,0.
};
int detau[128]={
0,0,0,3,0,3,3,31, 0,3,3,21,3,3,29,30,
0,3,3,20,3,25,27,26, 3,23,58,22,3,24,28,3,
0,3,3,3,3,39,33,32, 3,37,35,36,3,38,34,3,
3,42,46,44,50,40,48,3, 54,3,56,3,52,3,3,1,
0,3,3,108,3,78,100,104, 3,84,92,88,156,80,96,3,
3,74,70,72,66,76,68,3, 62,3,60,3,64,3,3,1,
3,116,132,112,148,152,3,3, 140,3,136,3,144,3,3,1,
124,120,128,3,3,3,3,1, 3,3,3,1,3,1,1,1
};
int detab7[32]={
4,11,18,25,32,39,46,53,60,66,72,77,82,87,92,96,101,
104,108,111,114,115,117,119,121,122,123,124,125,126,
127,127
};
float descl[8]={.6953,.6250,.5781,.5469,.5312,.5391,.4688,.3828};
int deadd[8]={1152,-2816,-1536,-3584,-1280,-2432,768,-1920};
int qb[8]={511,511,1023,1023,1023,1023,2047,4095};
int nbit[10]={8,8,5,5,4,4,4,4,3,2};
int zrc[MAXORD]={0,0,0,0,0,3,0,2,0,0};
int abit[5]={2,4,8,16,32};
extern int drc[3][MAXORD], dpit[3], drms[3];
decode(ipitv, irms, irc, voice, pitch, rms, rc )
int ipitv, *irms, irc[MAXORD];
int voice[2], *pitch;
float *rms, rc[ORDER];
{
int ivoic;
static int ivp2h=0, erate=0, iovoic=0;
int i, i1, i2, i4, iavgp=60, icorf,index, iout;
int ipit, ishift, ixcor, lsb, median();
int errcnt;
int ethrs=2048, ethrs1=128, ethrs2=1024, ethrs3=2048;
int fut=0, pres=1, past=2;
float ftemp;
int itemp;
static short first=1;
/* If no error correction, do pitch and voicing then jump to decode */
i4 = detau[ipitv];
/* Do error correction pitch and voicing */
if(i4>4) {
dpit[fut] = i4;
ivoic = 2;
iavgp = (15*iavgp+i4+8)*0.0625;
}
else {
ivoic = i4;
dpit[fut] = iavgp;
}
drms[fut] = *irms;
for(i=1;i<=ORDER;i++)
drc[fut][i-1] = irc[i];
/* Determine index to IVTAB from V/UV decision
* If error rate is high then use alternate table */
index = 16*ivp2h + 4*iovoic + ivoic + 1;
i1 = ivtab[index-1];
ipit = i1&3;
icorf = i1*0.125;
if(erate=0) drms[pres] = iout*2 + lsb;
for(i=1;i<=4;i++) {
if(i==1)
i1= (drc[pres][8]&7)*2+(drc[pres][9] &1);
else
i1 = drc[pres][8-i]&15;
i2 = drc[pres][4-i]&31;
lsb = i2&1;
index = 16*i1 + i2*0.5;
ham84(index,&iout,&errcnt);
if(iout>=0) {
iout = iout*2+lsb;
if((iout&16)==16)
iout = iout-32;
}
else
iout = drc[past][4-i];
drc[pres][4-i] = iout;
}
/* Determine error rate */
erate = erate*.96875 + errcnt*102;
}
/* Get unsmoothed RMS, RC's, and PITCH */
*irms = drms[pres];
for(i=1;i<=ORDER;i++)
irc[i]= drc[pres][i-1];
if(ipit==1) dpit[pres] = dpit[past];
if(ipit==3) dpit[pres] = dpit[fut];
*pitch = dpit[pres];
/* If bit 2 of ICORF is set then smooth RMS and RC's, */
if(icorf&abit[1]!=0) {
if( abs(drms[pres]-drms[fut]) >= corth[ixcor-1][1]
&& abs(drms[pres]-drms[past]) >= corth[ixcor-1][1] )
*irms = median( drms[past], drms[pres], drms[fut] );
for(i=1;i<=6;i++)
if( abs(drc[pres][i-1]-drc[fut][i-1]) >= corth[ixcor-1][i+1]
&&abs(drc[pres][i-1]-drc[past][i-1])>= corth[ixcor-1][i+1])
irc[i]= median( drc[past][i-1], drc[pres][i-1],drc[fut][i-1]);
}
/* If bit 3 of ICORF is set then smooth pitch */
if(icorf&abit[2]!=0) {
if(abs(dpit[pres]-dpit[fut]) >= corth[ixcor-1][0]
&&abs(dpit[pres]-dpit[past])>= corth[ixcor-1][0])
*pitch = median( dpit[past], dpit[pres], dpit[fut] );
}
/* If bit 5 of ICORF is set then RC(5) - RC(10) are loaded with
* values so that after quantization bias is removed in decode
* the values will be zero. */
} /* end if first */
if((icorf&abit[4])!=0)
for(i=5;i<=ORDER;i++)
irc[i]= zrc[i-1];
/* House keeping - one frame delay */
iovoic = ivoic;
ivp2h = voice[2];
dpit[past] = dpit[pres];
dpit[pres] = dpit[fut];
drms[past] = drms[pres];
drms[pres] = drms[fut];
for(i=1;i<=ORDER;i++) {
drc[past][i-1] = drc[pres][i-1];
drc[pres][i-1] = drc[fut][i-1];
}
/* Decode RMS */
*irms = rmst[(31-*irms)*2];
/* Decode RC(1) and RC(2) from log-area-ratios
* Protect from illegal coded value (-16) caused by bit errors */
for(i=1;i<=2;i++) {
i2 = irc[i];
i1 = 0;
if(i2<0) {
i1 = 1;
i2 = -i2;
if(i2>15) i2 = 0;
}
i2 = detab7[2*i2];
if(i1==1) i2 = -i2;
ishift = 15 - nbit[i-1];
/* irc[i]= i2*pow(2.0,(float)ishift); */
irc[i] = i2*(2<<(ishift-1));
}
/* Decode RC(3)-RC(10) to sign plus 14 bits */
for(i=3;i<=ORDER;i++) {
i2 = irc[i];
ishift = 15 - nbit[i-1];
/* i2 = i2*pow(2.0,(float)ishift); */
i2 = i2*(2<<(ishift-1));
i2 += qb[i-3];
ftemp = i2*descl[i-3] + deadd[i-3]; /* rounding problem */
if(ftemp < 0) {
ftemp = - ftemp;
itemp = ftemp;
irc[i] = -itemp;
}
else
irc[i] = ftemp;
}
/* Scale RMS and RC's to reals */
*rms = *irms;
for(i=1;i<=ORDER;i++)
rc[i]= (float)(irc[i]* 6.103515625e-05); /* 16,384 = 2**14 */
}