+void ff_amrwb_lsp2lpc(const double *lsp, float *lp, int lp_order)
+{
+ int lp_half_order = lp_order >> 1;
+ double buf[lp_half_order + 1];
+ double pa[lp_half_order + 1];
+ double *qa = buf + 1;
+ int i,j;
+
+ qa[-1] = 0.0;
+
+ ff_lsp2polyf(lsp , pa, lp_half_order );
+ ff_lsp2polyf(lsp + 1, qa, lp_half_order - 1);
+
+ for (i = 1, j = lp_order - 1; i < lp_half_order; i++, j--) {
+ double paf = pa[i] * (1 + lsp[lp_order - 1]);
+ double qaf = (qa[i] - qa[i-2]) * (1 - lsp[lp_order - 1]);
+ lp[i-1] = (paf + qaf) * 0.5;
+ lp[j-1] = (paf - qaf) * 0.5;
+ }
+
+ lp[lp_half_order - 1] = (1.0 + lsp[lp_order - 1]) *
+ pa[lp_half_order] * 0.5;
+
+ lp[lp_order - 1] = lsp[lp_order - 1];
+}
+