libpq Prepared Statement with dynamic IN operator

Dear All,
I am having a hard time figuring out how prepare and execute a Prepared Statement with an "IN" operator in the WHERE clause using libpq. The total elements that will be passed to IN operator is dynamic and varied at runtime.
here is an example query:

select payload_id,ptime,frequency from codecs where tag IN (‘G729’,’GSM’);

The number of elements to filter for with this particular example is 2 but this varies at runtime (between 1 to 127 elements).
I would like to know what’s the proper syntax of the (char *query) parameter when calling the PQprepare() function.
I tried “select payload_id,ptime,frequency from codecs where tag=ANY(?)” but failed

Regards,
Dave