Multimedia communications has gained an increasing interest in the last decade. The design of services and distributed multimedia applications imposes a number of Quality of Service (QoS) requirements. In particular, the processing and delivery of multimedia content are not independent and their interaction has a major impact on the QoS aspects. Recently, tracing watermarking has been proposed as a technique to provide a blind measure of the QoS of the communication, focusing on multimedia communication scenarios. This paper aims at presenting a review of recent patents, and state of art solutions as well, in the field of QoS assessment of multimedia communications by tracing watermarking. Finally, a discussion pointing out the current and future developments in this area summarizes the remarkable points of this work.