Manual:$wgDjvuDump

Details
Path to the djvudump executable.

To enable the rendering of DjVu files, both $wgDjvuRenderer and $wgDjvuDump must be set. Alternatively you could set $wgDjvuToXML instead of $wgDjvuDump. (If both $wgDjvuDump and $wgDjvuToXML are set, only $wgDjvuDump is used.)

Example: