-static void lsp2lpc_sipr(const double *lsp, float *Az)
-{
- int lp_half_order = LP_FILTER_ORDER >> 1;
- double buf[(LP_FILTER_ORDER >> 1) + 1];
- double pa[(LP_FILTER_ORDER >> 1) + 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_FILTER_ORDER - 1; i < lp_half_order; i++, j--) {
- double paf = pa[i] * (1 + lsp[LP_FILTER_ORDER - 1]);
- double qaf = (qa[i] - qa[i-2]) * (1 - lsp[LP_FILTER_ORDER - 1]);
- Az[i-1] = (paf + qaf) * 0.5;
- Az[j-1] = (paf - qaf) * 0.5;
- }
-
- Az[lp_half_order - 1] = (1.0 + lsp[LP_FILTER_ORDER - 1]) *
- pa[lp_half_order] * 0.5;
-
- Az[LP_FILTER_ORDER - 1] = lsp[LP_FILTER_ORDER - 1];
-}
-