ffmpeg helper not doing its stuff?

Hi:

I have video module working nicely I think - tho rather odd, to me, that don't see anything of quicktime movies I've posted till hit "Play"

But ffmpeg helper not helping so far.
Trying to set to use auto thumbnails, getting message telling me to give path to thumbnailer. I've tried googling for info, but can't find anything re this. (My host running linux I think)
Nor has it managed when supposedly finding sizes of uploaded videos: seeing nothing on Play, but can hear; seems this is as size set to zero.

I'd appreciate advice!

Martin