The File Helpers section of Retrieva's preferences allows you to set the association between files and those applications that can open them.

This way you can set Retrieva to recognize a kind of file by extension or by type, and how to respond when that file is viewed in Media View mode.

By setting a file to open externally in Media View mode, the file will open in the External Application that is designated to handle the media.

By setting a file to open internally, Retrieva will attempt to display the file contents in Media View mode according to the Internal Type setting such as image or video.

By checking the Store Whole File checkbox you can have Retrieva store the entire file in the media catalogue. If this is left unchecked Retrieva will simply reference the location of the file on the filesystem.