Combining accelerometer and video camera: Reconstruction of bow velocity profiles

A cost-effective method was developed for the estimation of the bow velocity in violin playing, using an accelerometer on the bow in combination with point tracking using a standard video camera. The video data are used to detect the moments of bow direction changes. This information is used for piece-wise integration of the accelerometer signal, resulting in a drift-free reconstructed velocity signal with a high temporal resolution. The method was evaluated using a 3D motion capturing system, providing a reliable reference of the actual bow velocity. The method showed good results when the accelerometer and video stream are synchronized. Additional latency and jitter of the camera stream can importantly decrease the performance of the method, depending on the bow stroke type.