post formats in custom post types

Hi everyone

I’m currently working on a theme for my website. Users can post stories, videos or photos on the website. I want to create a custom post type for each of the three categories, namely videos ( using video post format ), photos (using gallery post format) and stories (using the standard default post format). What I need to do is that when a user add a video post using the custom video post type, the post must automatically be posted as video post format. I don’t want it to be selectable like in the normal post screen, but rather hidden and by default either video, standard or gallery. One last thing, there will be sub categories that the user can choose from in each of the three categories, I want only the sub categories to be displayed for the chosen category’s custom post type, ie video custom post type to display only video’s sub categories

Any help will be appreciated

Many thanks