her in MPEG-2 and MPEG-4, follow the same pattern regarding compression of the video content. Typically the video is orga- nized in series of pictures (called frames) which appear 25 or 30 times per second (at equidistant time intervals), according to the legacy TV standards from the twentieth century. Each such picture is compressed by removing its redundancy with respect to other parts of the same picture or in regard to other neighboring pictures. In MPEG stan- dards there are reference pictures, which are not coded in respect to the other pictures (i.e. frames), and such frames are highest in size and are referred to as "I" frames (accord- ing to the MPEG terminology). Besides the reference frames, there are "P" pictures, which are compressed by removing temporal redundancy in respect to neighboring "I" frames. Finally, MPEG also has "B" pictures in which temporal redundancy in respect to neighboring "P" and "I" frames is removed. Hence, "B" frames are on average smallest, while "P" frames have sizes between the size of "B" and "I" frames, and "I" frames have the largest average size. Of course, all pictures are also spatially compressed by removing as much as possible of their own redundancy. Why is the approach used in video codecs such as MPEG important for video traf- fic? From the 1990s onwards almost all video codecs were based on various versions of the MPEG standards. For example, MPEG-4 is currently the most used video coding standard (it also includes audio coding, where audio typically accompanies the video traffic) and it absorbs all features of the previous MPEG standards (note that there is no MPEG-3 standard). In fact, MPEG-4 is an umbrella standard, which was standard- ized in 1998 by ISO (International Organization for Standardization); since then many new parts of the standards have been standardized (over 30 such parts of MPEG-4 were standardized by ISO in the first two decades after the initial standard and their number continues to grow). Then, bearing in mind the type of pictures in MPEG