pitsyn.c

this the source code of audio compression standard LPC. It is coded by C.

/*******************************************************************
*
*	PITSYN Version 53
*
*******************************************************************
*
*   Synthesize a single pitch epoch
*
* Inputs:
*  ORDER  - Synthesis order (number of RC's)
*  VOICE  - Half frame voicing decisions
*  PITCH  - Pitch
*  RMS    - Energy
*  RC     - Reflection coefficients
*  LFRAME - Length of speech buffer
* Outputs:
*  IVUV   - Pitch epoch voicing decisions
*  IPITI  - Pitch epoch length
*  RMSI   - Pitch epoch energy
*  RCI    - Pitch epoch RC's
*  NOUT   - Number of pitch periods in this frame
*  RATIO  - Previous to present energy ratio
*/

#include "config.ch"
#include "lpcdefs.h"
#include <math.h>


pitsyn(voice, pitch, rms, rc, ivuv, ipiti, rmsi, rci, nout, ratio )
int voice[], *pitch;
int ivuv[], ipiti[], *nout;
float *rms, rc[], rmsi[], rci[ORDER][11], *ratio;
{
static float rco[MAXORD], yarc[MAXORD];
int i, j, lsamp, ip, istart, ivoice;
static int ivoico=0, ipito=0;
int jused, nl;
static int jsamp;
float alrn, alro, prop;
static float rmso=0;
float slope, uvpit, vflag, xxy;
static short first=1;



if (*rms<1) *rms = 1;
if (rmso<1) rmso = 1;
uvpit = 0.0;
*ratio = *rms/(rmso+8.);

if (first) {	/*1*/
	lsamp = 0;
	ivoice = voice[2];
  if (ivoice==0) {
    *pitch = LFRAME*0.25;
  }
	*nout = LFRAME/ *pitch;
	jsamp = LFRAME - *nout * *pitch;
	for(i=1;i<=*nout;i++)	{
		for(j=1;j<=ORDER;j++)
			rci[j-1][i-1] = rc[j];
		ivuv[i] = ivoice;
		ipiti[i] = *pitch;
		rmsi[i] = *rms;
	}
	first = 0;
} /*1*/
else	{ /*1*/
	vflag = 0;
	lsamp = LFRAME + jsamp;
	slope = (*pitch-ipito)/(float)lsamp;
	*nout = 0;
	jused = 0;
	istart = 1;
	if ((voice[1]==ivoico)&&(voice[2]==voice[1])) { /*2*/
		if (voice[2]==0) {
/* SSUV - -   0  ,  0  ,  0	*/
			*pitch = LFRAME*0.25;
			ipito = *pitch;
			if( *ratio>8 ) rmso = *rms;
		}
/* SSVC - -   1  ,  1  ,  1	*/
		slope = (*pitch-ipito)/(float)lsamp;
		ivoice = voice[2];
	} /*2*/
	else	{ /*2*/
		if (ivoico!=1) {
			if (ivoico==voice[1])
/* UV2VC2 - -  0  ,  0  ,  1	*/
				nl = lsamp - LFRAME*0.25;
			else
/* UV2VC1 - -  0  ,  1  ,  1	*/
				nl = lsamp - 3*LFRAME*0.25;

			ipiti[1] = nl*0.5;
			ipiti[2] = nl - ipiti[1];
			ivuv[1] = 0;
			ivuv[2] = 0;
			rmsi[1] = rmso;
			rmsi[2] = rmso;
			for(i=1;i<=ORDER;i++)	{
				rci[i-1][0] = rco[i-1];
				rci[i-1][1] = rco[i-1];
				rco[i-1]   = rc[i];
			}
			slope = 0;
			*nout = 2;
			ipito = *pitch;
			jused = nl;
			istart = nl + 1;
			ivoice = 1;
		}
		else	{
			if (ivoico!=voice[1]) 
/* VC2UV1 - -   1  ,  0  ,  0	*/
				lsamp = LFRAME*0.25 + jsamp;
			else
/* VC2UV2 - -   1  ,  1  ,  0	*/
				lsamp = 3*LFRAME*0.25 + jsamp;

			for(i=1;i<=ORDER;i++)	{
				yarc[i-1] = rc[i];
				rc[i] = rco[i-1];
			}
			ivoice = 1;
			slope = 0.;
			vflag = 1;
		}
	} /*2*/


	while (1)	{	/*3*/
		for(i=istart;i<=lsamp;i++)	{ /*4*/
			ip = ipito + slope*i + .5;
			if (uvpit!=0.0) ip = uvpit;
			if (ip<=i-jused) { /*5*/	
				(*nout)++;
				if (*nout > 11) {
#ifdef TURBO
					 printf("PITSYN: too many epochs\n");
#endif
					exit(1);
				}
				ipiti[*nout] = ip;
				*pitch = ip;
				ivuv[*nout] = ivoice;
				jused += ip;
				prop = (jused-ip*0.5)/(float)lsamp;
				for(j=1;j<=ORDER;j++)	{
					alro = log((1+rco[j-1])/(1-rco[j-1]));
					alrn = log((1+rc[j])/(1-rc[j]));
					xxy = alro + prop*(alrn-alro);
					xxy = exp(xxy);
					rci[j-1][*nout-1] = (xxy-1)/(xxy+1);
				}
				rmsi[*nout]=log(rmso)+prop*(log(*rms)-log(rmso));
				rmsi[*nout] = exp(rmsi[*nout]);
			}	/*5*/
		} /*4*/
		if (vflag!=1) break;
		vflag = 0;
		istart = jused + 1;
		lsamp = LFRAME + jsamp;
		slope = 0;
		ivoice = 0;
		uvpit = (lsamp-istart)*0.5;
		if(uvpit>90) uvpit *= 0.5;
		rmso = *rms;
		for(i=1;i<=ORDER;i++)	{
			rc[i] = yarc[i-1];
			rco[i-1] = yarc[i-1];
		}
	}/*3*/
	jsamp = lsamp - jused;
} /*1*/
if (*nout!=0) {
	ivoico = voice[2];
	ipito = *pitch;
	rmso = *rms;
	/*DO I = 1,ORDER */
	for(i=1;i<=ORDER;i++)
		rco[i-1] = rc[i];
}

}