Watermarking is known to be a very di cult task. Robustness, Distortion, Payload, Security, Complexity are many constraints to deal with. When applied to a video stream, the di culty seems to be growing in comparison to image watermarking. Many classical non malicious manipulations of a compressed stream may suppress the embedded information. For example, a simple re-compression of a DVD movie (MPEG2 compression) to a DivX movie will defeat most of the current state-of-the-art watermarking systems. In this talk, we will expose the di erent techniques in order to watermark a video compressed stream. Before, we will present the H.264/AVC standard which is one of the most powerful video-compression algorithms. The discussion about video watermarking will be illustrated with H.264 streams. The speci c example of traitor tracing will be presented. Deadlocks will be discussed, and then the possible extensions and the future applications will conclude the presentation.