MPEG-2 is a series of standards that define video compression, audio compression, multiplexing and a variety of other related functions.MPEG-2 video is a joint standard developed by both the ITU-T and the ISO/IEC. It is published jointly as ISO/IEC 13818-2 and as ITU-T Rec. H.262.

MPEG-2 improves upon MPEG-1 by supporting higher data rates and streaming applications. MPEG-2 was primarily developed for digital terrestrial, satellite and cable television as well as Digital Video Disks (DVD).

In MPEG-2, the image is divided into macroblocks consisting of a 16×16 array of luma samples and an 8×8 array of chroma samples. Three types of frames are defined. I-Frames consist entirely of intra-coded macroblocks which do not depend on previous frames. I-Frames are often called Key Frames and provide randome access points within a video stream. P-Frames consist of macroblocks predicted from a previous I-Frame or other P-Frame. B-Frames consist of macroblocks which are predicted from a previous and a future I-Frame or P-Frame. The sequence of video images is broken into a Group of Pictures (GOP). Each GOP begins with an I-Frame followed by P-Frames and B-Frames. The next I-Frame is the beginning of the next GOP. A typical GOP might be: IBBPBBPBBPBB(I). Both P-Frames and B-frames use Motion Vectors to account for macroblock motion between the actual and reference images. Discrete Cosine transform (DCT) is then used on the five 8×8 blocks within each macroblock of the predicted image. Scalar quantization is used on the transform coefficients and Variable Length Coding (also called Entropy Coding) is used to remove statistical redundancy in the resulting values.

MPEG-2 is applicably to a wide range of applications and not all applications require all of the tools available in MPEG-2. For this reason, Profiles have been defined which group tools together for typical applications. Within each Profile, Levels are defined which constrain the range of quantitative capabilities such as resolution, frame rate and bit rate. MPEG-2 Profiles and Levels are shown in the table below.

MPEG-2 Systems (ISO/IEC 13818-1 and ITU-T Rec. H.222.0) defines the multiplexing layer which defines how video, audio and other data are formatted for distribution. The standard defines two formats. Transport Streams are typically used for real time streaming applications. Program Streams are typically used for storage applications.