The illegal copying of movies in the cinema is now common practice. Although the quality is fairly low, the economic impact of these illegal copies can be enormous. Philips' digital cinema watermarking scheme is designed for the upcoming digital cinema format and will assist content owners and distributors with tracing the origin of illegal copies. In this paper we consider this watermarking scheme in more detail. A characteristic of this watermarking scheme is that it only exploits the temporal axis to insert a watermark. It is therefore inherently robust to geometrical distortions, a necessity for surviving illegal copying by camcorder recording. Moreover, the scheme resists frame rate conversions resulting from a frame rate mismatch between the camcorder and the projector. The watermarking
scheme has been tested in a 'real' digital cinema environment with good results.