Convert AVI to BVH

Trying to convert Audio Video Interleave files directly to Biovision Hierarchy Animation files might be out of the ordinary and certainly not common, but appears to be doable.

You should be able to import simple animations in AVI format to a 3D animation software, which would be capable of importing/loading such files in order to generate 3D animations.

Try using tools, such as Poser, which should let users import AVI videos and re-save those as BVH animations.