From a game I developed years ago, I still have character models that my former 3D engine designer created and that I'd like to reuse in a Windows Phone project now.

However, the files are in DirectX format (.x) containing keyframe animation only. No bones. No skeleton.

There are a lot of animation keys defined on several frames to animate the characters.

I don't quite understand how that works, to be frankly. However, I did a lot of research regarding a possible way of getting the characters animated via XNA on Windows Phone and all I found are hints that it is generally possible but not supported. Possibly by implementing own Content Importers and Processors.

I didn't find anyone who successfully did something like that yet. How should I go about loading and displaying these models in XNA?