I am new to Mediatomb…

I have slightly modified a tutorial profile to strip the thumbnail from a jpeg image:
       <agent command="convert" arguments=" %in -strip %out"/>
If I use the convert command on the command line, the resulting image is fine. When I use Mediatomb to display the image, the thumbnail (which is what my display station, a freebox) is still there.

I don't know if the convert was attempted, or attempted but failed. It appears there's a log with Mediatomb, but I couldn't find it described in the documentation, in config.xml or in /var/log (I am running FreeBSD 8.1).