The paper describes watermarking of compressed video bitstreams. This technique is proven to be very fast and robust against various attacks including camcorder recording attack. The watermark is embedded using indirect modifications of transform coefficients in selected P- and B-frames. In the watermarked bitstream there exist sequences of watermarked pictures interleaved with sequences of unmodified pictures. The unmodified pictures serve as a reference for the watermark detection. The experimental results described for real-world MPEG-4 AVC/H.264 encoded HDTV video bitstreams are included.