Blender supports a huge number of various formats, however some of them may only be used with a proper add-on. One of these add-ons includes support for C3D and BVH formats and so it should be possible to convert one to another with Blender. Animation conversion.
Convert 3D biomechanics data standard to Biovision Hierarchy Animation file.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert c3d to bvh on Windows
A very popular free program used for work with 3D graphics
Convert from c3d file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.