Moving Picture Experts Group (acronym:MPEG) was formed by the ISO to set standards for audio and video compression and transmission.[1] Its first meeting was in May 1988 in Ottawa, Canada. As of late 2005, MPEG has grown to include approximately 350 members per meeting from various industries, universities, and research institutions. MPEG's official designation is ISO/IEC JTC1/SC29 WG11.
Contents |
Overview
The MPEG compression methodology is considered as asymmetric--where the encoder is more complex than the decoder.[2] The encoder needs to be algorithmic or adaptive whereas the decoder is 'dumb' and carries out fixed actions.[2] This is considered advantageous in applications such as broadcasting where the number of expensive complex encoders are small but the number of simple inexpensive decoders is large. This approach of the ISO to standardization in MPEG is considered novel because it is not the encoder which is standardized; instead, the way in which a decoder shall interpret the bitstream is defined. A decoder which can successfully interpret the bitstream is said to be compliant.[2] The advantage of standardizing the decoder is that over time encoding algorithms can improve yet compliant decoders will continue to function with them.[2] The MPEG standards give very little information regarding structure and operation of the encoder and implementers can supply encoders using proprietary algorithms.[3] This gives scope for competition between different encoder designs which means that better designs can evolve and users will have greater choice because of different levels of cost and complexity can exist in a range of coders yet a compliant decoder will operate with them all.[3]
MPEG also standardizes the protocol and syntax under which it is possible to combine or multiplex audio data with video data to produce a digital equivalent of a television program. Many such programs can be multiplexed and MPEG defines the way in which such multiplexes can be created and transported. The definitions include the metadata used by decoders to demultiplex correctly.[4]
Standards
The MPEG standards consist of different Parts. Each part covers a certain aspect of the whole specification.[5] The standards also specifies 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.[6] MPEG has standardized the following compression formats and ancillary standards:
- MPEG-1: is the first compression standard for audio and video. It was basically designed to allow moving pictures and sound to be encoded into the bitrate of a Compact Disc. To meet the low bit requirement, MPEG-1 downsamples the images, as well as using picture rates of only 24-30 Hz, resulting in a moderate quality.[7] It includes the popular Layer 3 (MP3) audio compression format.
- MPEG-2: 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. MPEG-2 is considered important because it has been chosen as the compression scheme for over-the-air digital television ATSC, DVB and ISDB, digital satellite TV services like Dish Network, digital cable television signals, SVCD, and DVD.[8]
- MPEG-3: Developments in standardizing scalable and multi-resolution compression which would have become MPEG-3 were ready by the time MPEG-2 was to be standardized; hence, these were incorporated into MPEG-2 and as a result there is no MPEG-3 standard.[9] MPEG-3 is not to be confused with MP3, which is MPEG-1 Audio Layer 3.
- MPEG-4: MPEG-4 uses further coding tools with additional complexity to achieve higher compression factors than MPEG-2.[10] In addition to more efficient coding of video, MPEG-4 moves closer to computer graphics applications. In more complex profiles, the MPEG-4 decoder effectively becomes a rendering processor and the compressed bitstream describes three-dimensional shapes and surface texture.[10] MPEG-4 also provides Intellectual Property Management and Protection (IPMP) which provides the facility to use proprietary technologies to manage and protect content like digital rights management.[11] Several new higher-efficiency video standards (newer than MPEG-2 Video) are included (an alternative to MPEG-2 Video), notably:
- MPEG-4 Part 2 (or Advanced Simple Profile) and
- MPEG-4 Part 10 (or Advanced Video Coding or H.264). MPEG-4 Part 10 may be used on HD DVD and Blu-ray discs, along with VC-1 and MPEG-2.
In addition, the following standards, while not sequential advances to the video encoding standard as with MPEG-1 through MPEG-4, are referred to by similar notation:
- MPEG-7: A multimedia content description standard.
- MPEG-21: MPEG describes this standard as a multimedia framework.
Moreover, relatively more recently than other standards above, MPEG has started following international standards; each of the standards holds multiple MPEG technologies for a way of application. For example, MPEG-A includes a number of technologies on multimedia application format.[12]
- MPEG-A: Multimedia application format.
- MPEG-B: MPEG systems technologies.
- MPEG-C: MPEG video technologies.
- MPEG-D: MPEG audio technologies.
- MPEG-E: Multimedia Middleware.
See also
Notes
- ^ John Watkinson, The MPEG Handbook p.1
- ^ a b c d John Watkinson, The MPEG Handbook, p.1
- ^ a b John Watkinson, The MPEG Handbook, p.2
- ^ John Watkinson, The MPEG Handbook, p.3
- ^ Understanding MPEG-4, p.78
- ^ Cliff Wootton. A Practical Guide to Video and Audio Compression. pp. p.665.
- ^ The MPEG Handbook, p.4
- ^ The MPEG Handbook, p.4
- ^ The MPEG Handbook, p.4
- ^ a b The MPEG Handbook, pp.4-5
- ^ Understanding MPEG-4, p.83
- ^ Official MPEG Web Site
External links
|
|||||
|
|||||||||||||||||||||||||||||||||||||||||||
No comments have been added.
