void ff_acelp_lspd2lpc(const double *lsp, float *lpc) { double pa[6], qa[6]; int i; lsp2polyf(lsp, pa, 5); lsp2polyf(lsp + 1, qa, 5); for (i=4; i>=0; i--) { double paf = pa[i+1] + pa[i]; double qaf = qa[i+1] - qa[i]; lpc[i ] = 0.5*(paf+qaf); lpc[9-i] = 0.5*(paf-qaf); } }