This work presents the first worst-case execution times (WCET) analysis of MPEG-decoding. Solutions for two scenarios (Video-on-Demand (VoD), live) are presented, serving as examples for a variety of real-world applications. A significant reduction of overestimations (down to ½ ±, including overhead) during WCET analysis of the live scenario can be achieved by using our new two-phase decoder with built-in WCET analysis that can be universally applied. It is even possible to predict the exact execution times in the VoD scenario. This work is motivated by the fact that media streaming service providers are under great pressure to fulfil the quality-of-service promised to their customers, preferably in an efficient way.