/* Evaluates the LPC amplitude spectrum envelope from the line spectrum pairs.  */
static void eval_lpcenv(TwinContext *tctx, const float *cos_vals, float *lpc)
/* Evaluates the LPC amplitude spectrum envelope from the line spectrum pairs.  */
static void eval_lpcenv(TwinContext *tctx, const float *cos_vals, float *lpc)
{
    int i;
    const ModeTab *mtab = tctx->mtab;
    int size_s = mtab->size / mtab->fmode[FT_SHORT].sub;
    for (i = 0; i < size_s/2; i++) {
        float cos_i = tctx->cos_tabs[0][i];
        lpc[i]          = eval_lpc_spectrum(cos_vals,  cos_i, mtab->n_lsp);
        lpc[size_s-i-1] = eval_lpc_spectrum(cos_vals, -cos_i, mtab->n_lsp);
    }
}