I have some audiobooks that are in MP4 format: they have chapter headings with pictures. They will not open on my Pre3. They open OK on my mac, and on an iphone. I also tried .m4v, .m4a and .m4b format too. Tried Quicktime conversion to iphone, and Handbrake conversion also, but they wont open. Is there an alternative I haven't tried? I see other threads suggesting Kalemsoft media player, but I cant find that in the HP app catalogue.