Comment 13 for bug 890059

@hvdwolf:
The 'So replace digikams debian/control ...' is for the guys doing the .deb packing,
not for users. For you it translates into install (k)ffmpegthumbs pkg. What you've done already.

If you replace kde-open with your favorite image viewer and generated thumbnail
of an mp4, that has no icon in digikam, is okay, then I have no glue what goin' wrong in your case :-(