MPEG-2

     MPEG-2 (1994) is the designation for a group of coding standards for digital audio and video, agreed upon by MPEG (Moving Pictures Experts Group), and published as the ISO/IEC 13818 international standard. MPEG-2 is typically used to encode audio and video for broadcast signals, including direct broadcast satellite and Cable TV. MPEG-2, with some modifications, is also the coding format used by standard commercial DVD movies.

     MPEG-2 includes a Systems part (part 1) that defines Transport Streams, which are designed to carry digital video and audio over somewhat-unreliable media, and are used in broadcast applications.

      The Video part (part 2) of MPEG-2 is similar to MPEG-1, but also provides support for interlaced video (the format used by broadcast TV systems). MPEG-2 video is not optimized for low bit-rates (less than 1 Mbit/s), but outperforms MPEG-1 at 3 Mbit/s and above. All standards-conforming MPEG-2 Video decoders are fully capable of playing back MPEG-1 Video streams.

     With some enhancements, MPEG-2 Video and Systems are also used in most HDTV transmission systems.

     The MPEG-2 Audio part (defined in Part 3 of the standard), enhances MPEG-1's audio by allowing the coding of audio programs with more than two channels. Part 3 of the standard allows this to be done in a backwards compatible way, allowing MPEG-1 audio decoders to decode the two main stereo components of the presentation.

     In part 7 of the MPEG-2 standard, audio can alternatively be coded in a non-backwards-compatible way, which allows encoders to make better use of available bandwidth. Part 7 is referred to as MPEG-2 AAC.