Unable to make it work edit

I'm unable to make this work. It looks a lot like PdfHandler, which is working on my site.

I've checked permissions, installed necessary binaries, etc. to no avail.

In one attempt to "fix" it, I factored out references to the binaries as $wgMogrify and $wgFfmpeg, then defined their full path, thinking that would help, but no dice.