Blender has had BVH Import since 2006, But since there was no exporting blender couldn’t be used for cleaning up BVH files, or as a MoCap editor.BVH Support
This is significant because, unlike mesh formats there are few well supported formats for moving armature animation between applications.
Until recently with FBX/Collada there was no support for exporting armature animation out of blender at all.

The other day I was contacted out of the blue by Andrea Rugliancich with a working BVH Motion Capture exporter for blender 2.49.

After some emails back and forth we I was about to accept the patch and also ported it to 2.56.

This was based on a script I started back in 2005 but never managed to finish, logically I couldn’t see why it was so complicated since I’d written a working importer but eventually I gave up and put the script online.
Since then I’ve seen a few modifications to it but none worked correctly.

So thanks to Andrea Rugliancich, for finishing a script started 6 years ago :)

PS, I realize blender needs many other tools to really be useful for cleaning up mocap data, but many of these could be written as scripts.
Probably the trickiest think is a good work-flow for re-target one armature to another, so as to be able to import a BVH and apply to an existing rig.

- Campbell (ideasman42)