Tracing watermarking for multimedia communication quality assessment

Multimedia data hiding by digital watermarking is usually employed for copyright protection purposes. In this contribution, a new application of watermarking is presented. Specifically, watermarking is here employed as a technique for testing the quality of service in multimedia mobile communications. A fragile known watermark is embedded in a MPEG-like host data video transport stream using a spread-spectrum technique to avoid visual interference. Like a tracing signal, a (known) tracing watermark tracks the (unknown) information stream that follows the same communication link. The detection of the tracing watermark allows dynamically evaluating the effective quality of the provided video services, depending on the whole physical layer (including the employed image co/decoder). The performed method is based on the mean-square-error between estimated and actual watermarks. The devised technique has been usefully applied to typical scenarios of mobile wireless multimedia communication systems, in presence of multipath channel and interfering users.