Synchronization constitutes an important research field in multimedia communication. The synchronization problem has been addressed in the literature in two distinct levels: specification and design. On the specification level, several formal models have been proposed, which are mostly variations of the Petri net model. Although some models are deemed to be better than others in some aspects, there has not been a comprehensive comparison of these specification models. This paper provides a critical review of the existing Petri net specification approaches for specifying synchronization constraints, including object composition, extended object composition, dynamic timed and time stream Petri net models, and applies them to the specification of an interesting, relatively straightforward synchronization example for a qualitative and quantitative evaluation of their strengths and weaknesses