void lsp_to_lpc(spx_lsp_t *freq,spx_coef_t *ak,int lpcrdr, char *stack)
/* float *freq array of LSP frequencies in the x domain */
/* float *ak array of LPC coefficients */
/* int lpcrdr order of LPC coefficients */
{
int i,j;
float xout1,xout2,xin1,xin2;
float *Wp;
float *pw,*n1,*n2,*n3,*n4=NULL;
float *x_freq;
int m = lpcrdr>>1;
Wp = PUSH(stack, 4*m+2, float);
pw = Wp;
/* initialise contents of array */
for(i=0;i<=4*m+1;i++){ /* set contents of buffer to 0 */
*pw++ = 0.0;
}
/* Set pointers up */
pw = Wp;
xin1 = 1.0;
xin2 = 1.0;
x_freq=PUSH(stack, lpcrdr, float);
for (i=0;i<lpcrdr;i++)
x_freq[i] = ANGLE2X(freq[i]);
/* reconstruct P(z) and Q(z) by cascading second order
polynomials in form 1 - 2xz(-1) +z(-2), where x is the
LSP coefficient */
for(j=0;j<=lpcrdr;j++){
int i2=0;
for(i=0;i<m;i++,i2+=2){
n1 = pw+(i*4);
n2 = n1 + 1;
n3 = n2 + 1;
n4 = n3 + 1;
xout1 = xin1 - 2.f*x_freq[i2] * *n1 + *n2;
xout2 = xin2 - 2.f*x_freq[i2+1] * *n3 + *n4;
*n2 = *n1;
*n4 = *n3;
*n1 = xin1;
*n3 = xin2;
xin1 = xout1;
xin2 = xout2;
}
xout1 = xin1 + *(n4+1);
xout2 = xin2 - *(n4+2);
ak[j] = (xout1 + xout2)*0.5f;
*(n4+1) = xin1;
*(n4+2) = xin2;
xin1 = 0.0;
xin2 = 0.0;
}
}
void lsp_to_lpc(spx_lsp_t *freq,spx_coef_t *ak,int lpcrdr, char *stack)
/* float *freq array of LSP frequencies in the x domain */
/* float *ak array of LPC coefficients */
/* int lpcrdr order of LPC coefficients */
{
int i,j;
spx_word32_t xout1,xout2,xin;
spx_word32_t mult, a;
VARDECL(spx_word32_t *xpmem);
VARDECL(spx_word32_t *xqmem);
#ifndef FIXED_LPC_SIZE
VARDECL(spx_word16_t *freqn);
VARDECL(spx_word32_t **xp);
VARDECL(spx_word32_t **xq);
#else
spx_word16_t freqn[FIXED_LPC_SIZE];
spx_word32_t *xp[(FIXED_LPC_SIZE/2)+1];
spx_word32_t *xq[(FIXED_LPC_SIZE/2)+1];
#endif
int m = lpcrdr>>1;
/*
Reconstruct P(z) and Q(z) by cascading second order polynomials
in form 1 - 2cos(w)z(-1) + z(-2), where w is the LSP frequency.
In the time domain this is:
y(n) = x(n) - 2cos(w)x(n-1) + x(n-2)
This is what the ALLOCS below are trying to do:
int xp[m+1][lpcrdr+1+2]; // P matrix in QIMP
int xq[m+1][lpcrdr+1+2]; // Q matrix in QIMP
These matrices store the output of each stage on each row. The
final (m-th) row has the output of the final (m-th) cascaded
2nd order filter. The first row is the impulse input to the
system (not written as it is known).
The version below takes advantage of the fact that a lot of the
outputs are zero or known, for example if we put an inpulse
into the first section the "clock" it 10 times only the first 3
outputs samples are non-zero (it's an FIR filter).
*/
#ifndef FIXED_LPC_SIZE
ALLOC(xp, (m+1), spx_word32_t*);
#endif
ALLOC(xpmem, (m+1)*(lpcrdr+1+2), spx_word32_t);
#ifndef FIXED_LPC_SIZE
ALLOC(xq, (m+1), spx_word32_t*);
#endif
ALLOC(xqmem, (m+1)*(lpcrdr+1+2), spx_word32_t);
#ifndef FIXED_LPC_SIZE
for(i=0; i<=m; i++) {
xp[i] = xpmem + i*(lpcrdr+1+2);
xq[i] = xqmem + i*(lpcrdr+1+2);
}
#else
for(i=0; i<=m; i++) {
xp[i] = xpmem + i*(FIXED_LPC_SIZE+1+2);
xq[i] = xqmem + i*(FIXED_LPC_SIZE+1+2);
}
#endif
/* work out 2cos terms in Q14 */
#ifndef FIXED_LPC_SIZE
ALLOC(freqn, lpcrdr, spx_word16_t);
for (i=0;i<lpcrdr;i++)
freqn[i] = ANGLE2X(freq[i]);
#else
for (i=0;i<FIXED_LPC_SIZE;i++)
freqn[i] = ANGLE2X(freq[i]);
#endif
#define QIMP 21 /* scaling for impulse */
xin = SHL32(EXTEND32(1), (QIMP-1)); /* 0.5 in QIMP format */
/* first col and last non-zero values of each row are trivial */
for(i=0;i<=m;i++) {
xp[i][1] = 0;
xp[i][2] = xin;
xp[i][2+2*i] = xin;
xq[i][1] = 0;
xq[i][2] = xin;
xq[i][2+2*i] = xin;
}
/* 2nd row (first output row) is trivial */
xp[1][3] = -MULT16_32_Q14(freqn[0],xp[0][2]);
xq[1][3] = -MULT16_32_Q14(freqn[1],xq[0][2]);
xout1 = xout2 = 0;
/* now generate remaining rows */
for(i=1;i<m;i++) {
for(j=1;j<2*(i+1)-1;j++) {
mult = MULT16_32_Q14(freqn[2*i],xp[i][j+1]);
xp[i+1][j+2] = ADD32(SUB32(xp[i][j+2], mult), xp[i][j]);
mult = MULT16_32_Q14(freqn[2*i+1],xq[i][j+1]);
xq[i+1][j+2] = ADD32(SUB32(xq[i][j+2], mult), xq[i][j]);
}
/* for last col xp[i][j+2] = xq[i][j+2] = 0 */
mult = MULT16_32_Q14(freqn[2*i],xp[i][j+1]);
xp[i+1][j+2] = SUB32(xp[i][j], mult);
mult = MULT16_32_Q14(freqn[2*i+1],xq[i][j+1]);
xq[i+1][j+2] = SUB32(xq[i][j], mult);
}
/* process last row to extra a{k} */
#ifndef FIXED_LPC_SIZE
for(j=1;j<=lpcrdr;j++) {
#else
for(j=1;j<=FIXED_LPC_SIZE;j++) {
#endif
int shift = QIMP-13;
/* final filter sections */
a = PSHR32(xp[m][j+2] + xout1 + xq[m][j+2] - xout2, shift);
xout1 = xp[m][j+2];
xout2 = xq[m][j+2];
/* hard limit ak's to +/- 32767 */
if (a < -32767) a = -32767;
if (a > 32767) a = 32767;
ak[j-1] = (short)a;
}
}
#else
void lsp_to_lpc(spx_lsp_t *freq,spx_coef_t *ak,int lpcrdr, char *stack)
/* float *freq array of LSP frequencies in the x domain */
/* float *ak array of LPC coefficients */
/* int lpcrdr order of LPC coefficients */
{
int i,j;
float xout1,xout2,xin1,xin2;
VARDECL(float *Wp);
float *pw,*n1,*n2,*n3,*n4=NULL;
VARDECL(float *x_freq);
int m = lpcrdr>>1;
ALLOC(Wp, 4*m+2, float);
pw = Wp;
/* initialise contents of array */
for(i=0;i<=4*m+1;i++){ /* set contents of buffer to 0 */
*pw++ = 0.0;
}
/* Set pointers up */
pw = Wp;
xin1 = 1.0;
xin2 = 1.0;
ALLOC(x_freq, lpcrdr, float);
for (i=0;i<lpcrdr;i++)
x_freq[i] = ANGLE2X(freq[i]);
/* reconstruct P(z) and Q(z) by cascading second order
polynomials in form 1 - 2xz(-1) +z(-2), where x is the
LSP coefficient */
for(j=0;j<=lpcrdr;j++){
int i2=0;
for(i=0;i<m;i++,i2+=2){
n1 = pw+(i*4);
n2 = n1 + 1;
n3 = n2 + 1;
n4 = n3 + 1;
xout1 = xin1 - 2.f*x_freq[i2] * *n1 + *n2;
xout2 = xin2 - 2.f*x_freq[i2+1] * *n3 + *n4;
*n2 = *n1;
*n4 = *n3;
*n1 = xin1;
*n3 = xin2;
xin1 = xout1;
xin2 = xout2;
}
xout1 = xin1 + *(n4+1);
xout2 = xin2 - *(n4+2);
if (j>0)
ak[j-1] = (xout1 + xout2)*0.5f;
*(n4+1) = xin1;
*(n4+2) = xin2;
xin1 = 0.0;
xin2 = 0.0;
}
}
void lsp_to_lpc(spx_lsp_t *freq,spx_coef_t *ak,int lpcrdr, char *stack)
/* float *freq array of LSP frequencies in the x domain */
/* float *ak array of LPC coefficients */
/* int lpcrdr order of LPC coefficients */
{
int i,j;
spx_word32_t xout1,xout2,xin1,xin2;
spx_word32_t *Wp;
spx_word32_t *pw,*n1,*n2,*n3,*n4=NULL;
spx_word16_t *freqn;
int m = lpcrdr>>1;
freqn = PUSH(stack, lpcrdr, spx_word16_t);
for (i=0;i<lpcrdr;i++)
freqn[i] = ANGLE2X(freq[i]);
Wp = PUSH(stack, 4*m+2, spx_word32_t);
pw = Wp;
/* initialise contents of array */
for(i=0;i<=4*m+1;i++){ /* set contents of buffer to 0 */
*pw++ = 0;
}
/* Set pointers up */
pw = Wp;
xin1 = 1048576;
xin2 = 1048576;
/* reconstruct P(z) and Q(z) by cascading second order
polynomials in form 1 - 2xz(-1) +z(-2), where x is the
LSP coefficient */
for(j=0;j<=lpcrdr;j++){
spx_word16_t *fr=freqn;
for(i=0;i<m;i++){
n1 = pw+(i<<2);
n2 = n1 + 1;
n3 = n2 + 1;
n4 = n3 + 1;
xout1 = ADD32(SUB32(xin1, MULT16_32_Q14(*fr,*n1)), *n2);
fr++;
xout2 = ADD32(SUB32(xin2, MULT16_32_Q14(*fr,*n3)), *n4);
fr++;
*n2 = *n1;
*n4 = *n3;
*n1 = xin1;
*n3 = xin2;
xin1 = xout1;
xin2 = xout2;
}
xout1 = xin1 + *(n4+1);
xout2 = xin2 - *(n4+2);
/* FIXME: perhaps apply bandwidth expansion in case of overflow? */
if (xout1 + xout2>256*32766)
ak[j] = 32767;
else if (xout1 + xout2 < -256*32767)
ak[j] = -32768;
else
ak[j] = PSHR(ADD32(xout1,xout2),8);
*(n4+1) = xin1;
*(n4+2) = xin2;
xin1 = 0;
xin2 = 0;
}
}
void lsp_to_lpc(const spx_lsp_t *freq,spx_coef_t *ak,int lpcrdr, char *stack)
/* float *freq array of LSP frequencies in the x domain */
/* float *ak array of LPC coefficients */
/* int lpcrdr order of LPC coefficients */
{
int i,j;
spx_word32_t xout1,xout2,xin;
spx_word32_t mult, a;
VARDECL(spx_word16_t *freqn);
VARDECL(spx_word32_t **xp);
VARDECL(spx_word32_t *xpmem);
VARDECL(spx_word32_t **xq);
VARDECL(spx_word32_t *xqmem);
int m = lpcrdr>>1;
/*
Reconstruct P(z) and Q(z) by cascading second order polynomials
in form 1 - 2cos(w)z(-1) + z(-2), where w is the LSP frequency.
In the time domain this is:
y(n) = x(n) - 2cos(w)x(n-1) + x(n-2)
This is what the ALLOCS below are trying to do:
int xp[m+1][lpcrdr+1+2]; // P matrix in QIMP
int xq[m+1][lpcrdr+1+2]; // Q matrix in QIMP
These matrices store the output of each stage on each row. The
final (m-th) row has the output of the final (m-th) cascaded
2nd order filter. The first row is the impulse input to the
system (not written as it is known).
The version below takes advantage of the fact that a lot of the
outputs are zero or known, for example if we put an inpulse
into the first section the "clock" it 10 times only the first 3
outputs samples are non-zero (it's an FIR filter).
*/
ALLOC(xp, (m+1), spx_word32_t*);
ALLOC(xpmem, (m+1)*(lpcrdr+1+2), spx_word32_t);
ALLOC(xq, (m+1), spx_word32_t*);
ALLOC(xqmem, (m+1)*(lpcrdr+1+2), spx_word32_t);
for(i=0; i<=m; i++) {
xp[i] = xpmem + i*(lpcrdr+1+2);
xq[i] = xqmem + i*(lpcrdr+1+2);
}
/* work out 2cos terms in Q14 */
ALLOC(freqn, lpcrdr, spx_word16_t);
for (i=0;i<lpcrdr;i++)
freqn[i] = ANGLE2X(freq[i]);
#define QIMP 21 /* scaling for impulse */
xin = SHL32(EXTEND32(1), (QIMP-1)); /* 0.5 in QIMP format */
/* first col and last non-zero values of each row are trivial */
for(i=0;i<=m;i++) {
xp[i][1] = 0;
xp[i][2] = xin;
xp[i][2+2*i] = xin;
xq[i][1] = 0;
xq[i][2] = xin;
xq[i][2+2*i] = xin;
}
/* 2nd row (first output row) is trivial */
xp[1][3] = -MULT16_32_Q14(freqn[0],xp[0][2]);
xq[1][3] = -MULT16_32_Q14(freqn[1],xq[0][2]);
xout1 = xout2 = 0;
/* now generate remaining rows */
for(i=1;i<m;i++) {
for(j=1;j<2*(i+1)-1;j++) {
mult = MULT16_32_Q14(freqn[2*i],xp[i][j+1]);
xp[i+1][j+2] = ADD32(SUB32(xp[i][j+2], mult), xp[i][j]);
mult = MULT16_32_Q14(freqn[2*i+1],xq[i][j+1]);
xq[i+1][j+2] = ADD32(SUB32(xq[i][j+2], mult), xq[i][j]);
}
/* for last col xp[i][j+2] = xq[i][j+2] = 0 */
mult = MULT16_32_Q14(freqn[2*i],xp[i][j+1]);
xp[i+1][j+2] = SUB32(xp[i][j], mult);
mult = MULT16_32_Q14(freqn[2*i+1],xq[i][j+1]);
xq[i+1][j+2] = SUB32(xq[i][j], mult);
}
/* process last row to extra a{k} */
for(j=1;j<=lpcrdr;j++) {
int shift = QIMP-13;
/* final filter sections */
a = PSHR32(xp[m][j+2] + xout1 + xq[m][j+2] - xout2, shift);
xout1 = xp[m][j+2];
xout2 = xq[m][j+2];
/* hard limit ak's to +/- 32767 */
if (a < -32767) a = -32767;
if (a > 32767) a = 32767;
ak[j-1] = (short)a;
}
}