The MPEG standard and its different variants explained in simple terms.
The MPEG standards consist of different Parts. Each part covers a certain aspect of the whole specification. The standards also specify Profiles and Levels. Profiles are intended to define a set of tools that are available, and Levels define the range of appropriate values for the properties associated with them.
MPEG has standardized the following compression formats and ancillary standards:
Approved in 1993. The first MPEG compression standard for audio and video. It is commonly limited to about 1.5 Mbit/s. It was basically designed to allow moving pictures and sound to be encoded into the bitrate of a Compact Disc. It is used on Video CD and can be used for low-quality video on DVD Video. It was used in digital satellite/cable TV services before MPEG-2 became widespread. To meet the low bit requirement, MPEG-1 downsamples the images, as well as uses picture rates of only 2430 Hz, resulting in a moderate quality. It includes the MPEG-1 Audio Layer III (MP3) audio compression format.
Transport, video and audio standards for broadcast-quality television. MPEG-2 standard was considerably broader in scope and of wider appeal, supporting interlacing and high definition. video. The format has been widely adopted because of its flexibility, and it is currently used on the following applications:
- Satellite TV providers
- Digital Terrestrial Televison (ATSC, DVB, ISDB)
- Super Video CD
- Blu-ray (although MPEG-4 Part 10 is used for HD content)
MPEG-3 dealt with standardizing scalable and multi-resolution compression and was intended for HDTV compression but was found to be redundant and was merged with MPEG-2, as a result there is no MPEG-3 standard. MPEG-3 is not to be confused with MP3, which is MPEG-1 Audio Layer III.
MPEG-4 uses further coding tools with additional complexity to achieve higher compression factors than MPEG-2. In addition, MPEG-4 moves closer to computer graphics applications. MPEG-4 supports Intellectual Property Management and Protection (IPMP), which provides the facility to use proprietary technologies to manage and protect content like digital rights management
Several new higher-efficiency video standards (newer than MPEG-2 Video) are included, notably:
- MPEG-4 Part 2 (or Simple and Advanced Simple Profile)
- MPEG-4 AVC (or MPEG-4 Part 10 or H.264). MPEG-4 AVC may be used on HD DVD and Blu-ray Discs, along with VC-1 and MPEG-2.
MPEG-7 is a multimedia content description standard. This description will be associated with the content itself, to allow fast and efficient searching for material that is of interest to the user. MPEG-7 is formally called Multimedia Content Description Interface. Thus, it is not a standard which deals with the actual encoding of moving pictures and audio, like MPEG-1, MPEG-2 and MPEG-4. It uses XML to store metadata, and can be attached to timecode in order to tag particular events, or synchronise lyrics to a song, for example.