Abstract. In this paper, we propose a practical real-time video watermarking scheme for downscaling attack. We embed watermark into an arbitrary size of a host video and extract it from the watermarked video under a preset false error rate. Both watermark embedding and extraction are done in the uncompressed domain. Also, blind detector is used (i.e., no original video needs during the detection). As our watermarking system uses a video coder and decoder according to a format of an input video, it can be applicable to DCT-based coding videos (e.g., MPEG-2) as well as MPEG-1 and MPEG-4. Moreover, for a practical use both embedder and detector are developed as directshow filters that make it easy to connect after another within directshow applications. The payload of this system is totally 192 bits. PSNR after embedding is around 45dB for the host video that ranges from QVGA to High Definition (HD) size. Finally, several experimental results prove that the proposed scheme has good robu...