-float vorbis_lpc_from_curve(float *curve,float *lpc,lpc_lookup *l){
- int n=l->ln;
- int m=l->m;
- float *work=alloca(sizeof(float)*(n+n));
- float fscale=.5f/n;
- int i,j;
-
- /* input is a real curve. make it complex-real */
- /* This mixes phase, but the LPC generation doesn't care. */
- for(i=0;i<n;i++){
- work[i*2]=curve[i]*fscale;
- work[i*2+1]=0;
- }
- work[n*2-1]=curve[n-1]*fscale;
-
- n*=2;
- drft_backward(&l->fft,work);
-
- /* The autocorrelation will not be circular. Shift, else we lose
- most of the power in the edges. */
-
- for(i=0,j=n/2;i<n/2;){
- float temp=work[i];
- work[i++]=work[j];
- work[j++]=temp;