[mythtv] How to permanently flag a channel as unencrypted/encrypted without believing wrong dvb tables?

[Emmanuel]

Hi all,
I'd like a few pointers to understand how encrypted/unencrypted status 
is found and how it is updated. Indeed when the dvb tables are false 
(which is the case for me), you need to tell mythtv what is the 
encrypted status of certain channels permanently. In essence I'd like to 
code a "channel is (un)encrypted whatever is said by the dvb tables" 
button in mythtv-setup.
Thx
Bye
Manu