MPEG-2
Studies on MPEG-2 started in 1990 with the initial target to issue a standard for coding of TV-pictures with CCIR Rec. 601 resolution at data rates below 10 Mbit/s. In 1992 the scope of MPEG-2 was enlarged to suit coding of HDTV - thus making an initially planned MPEG-3 phase superfluous. The DIS for MPEG-2 video was issued in early 1994.

The video coding scheme used in MPEG-2 is again generic and similar to the one of MPEG-1, however with further refinements and special consideration of interlaced sources. Furthermore many functionalities such as "scalability" were introduced. In order to keep implementation complexity low for products not requiring the full video input formats supported by the standard (e.g. SIF to HDTV resolutions), so called "Profiles", describing functionalities, and "Levels", describing resolutions, were introduced to provide separate MPEG-2 conformance levels.

http://wwwam.hhi.de/mpeg-video/standards/mpeg-2.htm