The paper presents a novel video watermarking scheme called Mapping Energy video Watermarking (MEW) for copyright protection. The watermark is embedded in the compressed domain and extracted directly from the bitstream without original video. In the proposed scheme, we select a part of Integer DCT quantized coefficients to construct the embedded space and embed the watermark into it by using Energy Mapping Function (EMF). During the process of embedding, resynchronization strategy and watermarking coding are used to guarantee the robustness of watermarking. The experimental results indicate that the scheme has strong robustness to the attacks such as re-encoding, frame dropping, frame rate changing and sharpening. The influence of the coding efficiency is almost unnoticeable. Besides, high watermark payload and low time complexity are advantages of the scheme.