A new markerless mocap system has a demo video here:
“Captury Studio allows maximum flexibility during capture:
Use any camera: Captury Studio can handle any combination of cameras running at different framerates and resolutions. You can import videos in various file formats.
Capture anywhere: No specific background is necessary. Captury Studio can handle even dynamic scenes and changing illumination as long as sufficient color contrast between actors and background exists.
Capture anything: Captury Studio provides a highly optimized human body model that can be scaled to the size of any actor. Animals, objects, or machines can be tracked by generating customized skeleton and model definitions.”
its using background removal and some other jiggery pokery as can be seen here