[mythtv] Please explain the usage (valid arguments) of the mythfilldatabase "--sourceid" option

[Fox]

I am very confused by the mythfilldatabase "--sourceid" option.  My issue is that I have two different video sources (tuners that each receive a different set of channels because they are connected to antennas pointed in different directions), but the schedule data for all of the channels I can receive is in the same xmltv.xml file.  So if I use --sourceid 1 as some documents suggest (such as the wiki page at http://www.mythtv.org/wiki/Mythfilldatabase), only the data for one of those sources gets put into the schedule grid.

How can I get the schedule data for all the sources to go into the schedule grid?  I can't seem to find any list or explanation of the valid options for the "--sourceid" argument.  I wish the wiki page were just a bit less terse on that, but right now I don't truly understand how this works.

I did run the command
$ mysql -u root mythconverg
as suggested on the wiki page, and it revealed two sourceid's (1 and 2) so maybe my question should be, how do I put both of those into the "--sourceid" argument?  Would a syntax such as "--sourceid 1,2" or even "--sourceid all" be valid?