+ // To prevent long stretches of N's to be mistaken for indels (sometimes thousands of bases),
+ // check the number of N's in the sequence and skip places where half or more reference bases are Ns.
+ int nN=0; for (i=pos; i-pos<max_rd_len && ref[i]; i++) if ( ref[i]=='N' ) nN++;
+ if ( nN*2>i ) return -1;
+