Abstract skeletal animation in existing rendering engine

We have a custom game engine in C++. Until now, we are playing animations using multiple key frames, about 20 key-frames per second. We need to reduce it down to less than 5 for smooth rendering. For this we are making changes to our existing animation subsystem to incorporate any animation based on small number of key-frames. There are bugs that need to be fixed. We also need documentation for the changes implemented.