where to change -x part of transcode command

I'm having a hanging problem on the transcode "Grab Preview Image Command"
portion of the rip, which I have resolved to changing the -x option to
transcode, so this command portion :

...... execflow transcode  -H 10 --print_status 25 -o snapshot -y ppm,null
-x vob,null -i /opt/dvdrip/alien/vob/005/ -c 2-3 -L 3228 ....

needs to be

...... execflow transcode  -H 10 --print_status 25 -o snapshot -y ppm,null
-x mpeg2,null -i /opt/dvdrip/alien/vob/005/ -c 2-3 -L 3228 ....


I see a command getting setup in lib/Video/DVDRip/Title.pm, but not sure if
this is best to edit.



Thanks,
John