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channel.c
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C/C++ Source or Header
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2000-05-18
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/************************************************************************
*
* CHANL Version 49
*
************************************************************************
*
* CHANWR:
* Place quantized parameters into bitstream
*
* Inputs:
* ORDER - Number of reflection coefficients (not really variable)
* IPITV - Quantized pitch/voicing parameter
* IRMS - Quantized energy parameter
* IRC - Quantized reflection coefficients
* Output:
* IBITS - Serial bitstream
*
* CHANRD:
* Reconstruct parameters from bitstream
*
* Inputs:
* ORDER - Number of reflection coefficients (not really variable)
* IBITS - Serial bitstream
* Outputs:
* IPITV - Quantized pitch/voicing parameter
* IRMS - Quantized energy parameter
* IRC - Quantized reflection coefficients
*
* IBITS is 54 bits of LPC data ordered as follows:
* R1-0, R2-0, R3-0, P-0, A-0,
* R1-1, R2-1, R3-1, P-1, A-1,
* R1-2, R4-0, R3-2, A-2, P-2, R4-1,
* R1-3, R2-2, R3-3, R4-2, A-3,
* R1-4, R2-3, R3-4, R4-3, A-4,
* P-3, R2-4, R7-0, R8-0, P-4, R4-4,
* R5-0, R6-0, R7-1,R10-0, R8-1,
* R5-1, R6-1, R7-2, R9-0, P-5,
* R5-2, R6-2,R10-1, R8-2, P-6, R9-1,
* R5-3, R6-3, R7-3, R9-2, R8-3, SYNC
*/
#include "lpcdefs.h"
int bit[10] = {
2, 4, 8, 8, 8, 8, 16, 16, 16, 16
};
int iblist[53] = {
13, 12, 11, 1, 2, 13, 12, 11, 1, 2, 13, 10,
11, 2, 1, 10, 13, 12, 11, 10, 2, 13, 12, 11,
10, 2, 1, 12, 7, 6, 1, 10, 9, 8, 7, 4,
6, 9, 8, 7, 5, 1, 9, 8, 4, 6, 1, 5,
9, 8, 7, 5, 6
};
channel(which, ipitv, irms, irc, ibits )
int which, *ipitv, *irms, irc[ORDER], ibits[54];
{
int i;
static int isync;
int itab[13];
switch(which) {
case 0: /*chanwr*/
/************************************************************************
* Place quantized parameters into bitstream
************************************************************************
* Place parameters into ITAB */
itab[0] = *ipitv;
itab[1] = *irms;
itab[2] = 0;
for(i=1;i<=ORDER;i++)
itab[i+2] = irc[ORDER+1-i] & 32767 ;
/* Put 54 bits into IBITS array */
for(i=1;i<=53;i++) {
ibits[i] = itab[iblist[i-1]-1] & 1;
itab[iblist[i-1]-1] = itab[iblist[i-1]-1] >> 1;
}
ibits[54] = isync&1;
isync = 1 - isync;
break;
/************************************************************************
* Reconstruct parameters from bitstream
*************************************************************************/
case 1: /*chanwr*/
/* Reconstruct ITAB */
for(i=0;i<13;i++)
itab[i] = 0;
for(i=1;i<=53;i++)
itab[iblist[53-i]-1] = itab[iblist[53-i]-1]*2 + ibits[54-i];
/* Sign extend RC's */
for(i=1;i<=ORDER;i++)
if( (itab[i+2] & bit[i-1]) != 0 ) itab[i+2] -= 2*bit[i-1];
/* Restore variables */
*ipitv = itab[0];
*irms = itab[1];
for(i=1;i<=ORDER;i++)
irc[i] = itab[ORDER+3-i];
break;
}
}