A novel video watermarking method is proposed, which can directly embed a watermark into a bit stream generated by an H.264 video encoder. Watermarking to encoded data provides a content provider of flexible capability to attach secret information; however it brings a drift problem. A drift compensation method has been proposed, however it requires many computations such as DCT and motion compensation. Therefore a new drift compensation method with spatiotemporal watermarking is proposed that only cancels the effect of the embedding on blocks with little motion. It achieves great reduction of computation and realizes fast and high picture quality watermarking. The computer simulation shows that degradation of picture quality is negligible compared to noises due to H.264 compression, and that the proposed method is highly resilient to frequency domain attacks