Digital watermarking is a helpful technology for providing copyright protection for valuable multimedia data. In particular, video watermarking deals with several issues, which are unique to various types of media watermarking. In this paper, these issues, including compressed domain watermarking, real-time detection, bit-rate control, and resistance to watermark estimation attacks, will be addressed. Since video sequences are usually compressed before they are transmitted over networks, we first describe how watermark signals can be embedded into compressed video while keeping the desired bit-rate nearly unchanged. In the embedding process, our algorithm is designed to operate directly in the variable length codeword (VLC) domain to satisfy the requirement of real-time detection. We describe how suitable positions in the VLC domain can be selected for embedding transparent watermarks. Second, in addition to typical attacks, the peculiar attacks that video sequences encounter are investigated. In particular, in order to deal with both collusion and copy attacks that are fatal to video watermarking, the video frame-dependent watermark (VFDW) is presented. Extensive experimental results verify the excellent performance of the proposed compressed video watermarking system in addressing the aforementioned issues.