MPEG-4 Part 2
Encyclopedia
MPEG-4 Part 2, MPEG-4 Visual (formally ISO/IEC
14496-2) is a video compression technology developed by MPEG. It belongs to the MPEG-4
ISO/IEC standards. It is a discrete cosine transform
compression standard, similar to previous standards such as MPEG-1
and MPEG-2
. Several popular codec
s including DivX
, Xvid
and Nero Digital
implement this standard.
Note that MPEG-4 Part 10
defines a different format than MPEG-4 Part 2 and should not be confused with it. MPEG-4 Part 10 is commonly referred to as H.264 or AVC, and was jointly developed by ITU-T
and MPEG.
MPEG-4 Part 2 is H.263
compatible in the sense that a basic H.263 bitstream is correctly decoded by an MPEG-4 Video decoder. (MPEG-4 Video decoder is natively capable of decoding a basic form of H.263.) In MPEG-4 Visual, there are two types of video object layers: the video object layer that provides full MPEG-4 functionality, and a reduced functionality video object layer, the video object layer with short headers (which provides bitstream compatibility with base-line H.263). MPEG-4 Part 2 is partially based on ITU-T H.263. The first MPEG-4 Video Verification Model (simulation and test model) used ITU-T H.263 coding tools together with shape coding.
Most of the video compression schemes standardize the bitstream
(and thus the decoder
) leaving the encoder
design to the individual implementations. Therefore, implementations for a particular profile (such as DivX
or Nero Digital
which are implementations of Advanced Simple Profile and Xvid
that implements both profiles) are all technically identical on the decoder side. A point of comparison would be that an MP3 file can be played in any MP3 player, whether it was created through iTunes, Windows Media Player, LAME
or the common Fraunhofer encoder.
s, some low end video conferencing systems, electronic surveillance systems etc.
, include:
The MPEG quantization and interlace support are designed in basically similar ways to the way it is found in MPEG-2
Part 2. The B picture support is designed in a basically similar way to the way it is found in MPEG-2 Part 2 and H.263v2
.
The quarter-pixel motion compensation feature of ASP was innovative, and was later also included (in somewhat different forms) in MPEG-4 Part 10 and VC-1
. Some implementations omit support for this feature, because it has a significantly harmful effect on speed and it is not always beneficial for quality.
The global motion compensation feature is not actually supported in most implementations although the standard officially requires decoders to support it. Most encoders do not support it either, and some experts say that it does not ordinarily provide any benefit in compression. When used, ASP's global motion compensation has a large unfavorable impact on speed and adds considerable complexity to the implementation.
's maintainer Michael Niedermayer has criticised MPEG-4 for lacking an in-loop deblocking filter
, GMC being too computationally intensive, and OBMC being defined but not allowed in any profiles among other things. Microsoft
's Ben Waggoner states "Microsoft (well before my time) went down the codec standard route before with MPEG-4 part 2, which turns out to be a profound disappointment across the industry - it didn't offer that much of a compression advantage over MPEG-2, and the protracted license agreement discussions scared off a lot of adoption. I was involved in many digital media projects that wouldn't even touch MPEG-4 in the late '90s to early '00s because there was going to be a 'content fee' that hadn't been fully defined yet."
International Electrotechnical Commission
The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...
14496-2) is a video compression technology developed by MPEG. It belongs to the MPEG-4
MPEG-4
MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group under the formal standard ISO/IEC...
ISO/IEC standards. It is a discrete cosine transform
Discrete cosine transform
A discrete cosine transform expresses a sequence of finitely many data points in terms of a sum of cosine functions oscillating at different frequencies. DCTs are important to numerous applications in science and engineering, from lossy compression of audio and images A discrete cosine transform...
compression standard, similar to previous standards such as MPEG-1
MPEG-1
MPEG-1 is a standard for lossy compression of video and audio. It is designed to compress VHS-quality raw digital video and CD audio down to 1.5 Mbit/s without excessive quality loss, making video CDs, digital cable/satellite TV and digital audio broadcasting possible.Today, MPEG-1 has become...
and MPEG-2
MPEG-2
MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information". It describes a combination of lossy video compression and lossy audio data compression methods which permit storage and transmission of movies using currently available storage media and transmission...
. Several popular codec
Codec
A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...
s including DivX
DivX
DivX is a brand name of products created by DivX, Inc. , including the DivX Codec which has become popular due to its ability to compress lengthy video segments into small sizes while maintaining relatively high visual quality.There are two DivX codecs; the regular MPEG-4 Part 2 DivX codec and the...
, Xvid
XviD
Xvid is a video codec library following the MPEG-4 standard, specifically MPEG-4 Part 2 Advanced Simple Profile . It uses ASP features such as b-frames, global and quarter pixel motion compensation, lumi masking, trellis quantization, and H.263, MPEG and custom quantization matrices.Xvid is a...
and Nero Digital
Nero Digital
Nero Digital is a brand name applied to a suite of MPEG-4-compatible video and audio compression codecs developed by Nero AG of Germany and Ateme of France...
implement this standard.
Note that MPEG-4 Part 10
H.264/MPEG-4 AVC
H.264/MPEG-4 Part 10 or AVC is a standard for video compression, and is currently one of the most commonly used formats for the recording, compression, and distribution of high definition video...
defines a different format than MPEG-4 Part 2 and should not be confused with it. MPEG-4 Part 10 is commonly referred to as H.264 or AVC, and was jointly developed by ITU-T
ITU-T
The ITU Telecommunication Standardization Sector is one of the three sectors of the International Telecommunication Union ; it coordinates standards for telecommunications....
and MPEG.
MPEG-4 Part 2 is H.263
H.263
H.263 is a video compression standard originally designed as a low-bitrate compressed format for videoconferencing. It was developed by the ITU-T Video Coding Experts Group in a project ending in 1995/1996 as one member of the H.26x family of video coding standards in the domain of the ITU-T.H.263...
compatible in the sense that a basic H.263 bitstream is correctly decoded by an MPEG-4 Video decoder. (MPEG-4 Video decoder is natively capable of decoding a basic form of H.263.) In MPEG-4 Visual, there are two types of video object layers: the video object layer that provides full MPEG-4 functionality, and a reduced functionality video object layer, the video object layer with short headers (which provides bitstream compatibility with base-line H.263). MPEG-4 Part 2 is partially based on ITU-T H.263. The first MPEG-4 Video Verification Model (simulation and test model) used ITU-T H.263 coding tools together with shape coding.
Editions
| Edition | Release date | Latest amendment | Standard | Description |
|---|---|---|---|---|
| First edition | 1999 | 2000 | ISO/IEC 14496-2:1999 | |
| Second edition | 2001 | 2003 | ISO/IEC 14496-2:2001 | |
| Third edition | 2004 | 2009 | ISO/IEC 14496-2:2004 |
Profiles
To address various applications ranging from low-quality, low-resolution surveillance cameras to high definition TV broadcasting and DVDs, many video standards group features into profiles and levels. MPEG-4 Part 2 has approximately 21 profiles, including profiles called Simple, Advanced Simple, Main, Core, Advanced Coding Efficiency, Advanced Real Time Simple, etc. The most commonly deployed profiles are Advanced Simple and Simple, which is a subset of Advanced Simple.Most of the video compression schemes standardize the bitstream
Bitstream
A bitstream or bit stream is a time series of bits.A bytestream is a series of bytes, typically of 8 bits each, and can be regarded as a special case of a bitstream....
(and thus the decoder
Decoder
A decoder is a device which does the reverse operation of an encoder, undoing the encoding so that the original information can be retrieved. The same method used to encode is usually just reversed in order to decode...
) leaving the encoder
Encoder
An encoder is a device, circuit, transducer, software program, algorithm or person that converts information from one format or code to another, for the purposes of standardization, speed, secrecy, security, or saving space by shrinking size.-Media:...
design to the individual implementations. Therefore, implementations for a particular profile (such as DivX
DivX
DivX is a brand name of products created by DivX, Inc. , including the DivX Codec which has become popular due to its ability to compress lengthy video segments into small sizes while maintaining relatively high visual quality.There are two DivX codecs; the regular MPEG-4 Part 2 DivX codec and the...
or Nero Digital
Nero Digital
Nero Digital is a brand name applied to a suite of MPEG-4-compatible video and audio compression codecs developed by Nero AG of Germany and Ateme of France...
which are implementations of Advanced Simple Profile and Xvid
XviD
Xvid is a video codec library following the MPEG-4 standard, specifically MPEG-4 Part 2 Advanced Simple Profile . It uses ASP features such as b-frames, global and quarter pixel motion compensation, lumi masking, trellis quantization, and H.263, MPEG and custom quantization matrices.Xvid is a...
that implements both profiles) are all technically identical on the decoder side. A point of comparison would be that an MP3 file can be played in any MP3 player, whether it was created through iTunes, Windows Media Player, LAME
LAME
LAME is a free software codec used to encode/compress audio into the lossy MP3 file format.-History:The name LAME is a recursive acronym for "LAME Ain't an MP3 Encoder". Around mid-1998, Mike Cheng created LAME 1.0 as a set of modifications against the "8Hz-MP3" encoder source code...
or the common Fraunhofer encoder.
Simple Profile (SP)
Simple Profile is mostly aimed for use in situations where low bit rate and low resolution are mandated by other conditions of the applications, like network bandwidth, device size etc. Examples are mobile phoneMobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
s, some low end video conferencing systems, electronic surveillance systems etc.
Advanced Simple Profile (ASP)
Advanced Simple Profile 's notable technical features relative to the Simple Profile, which is roughly similar to H.263H.263
H.263 is a video compression standard originally designed as a low-bitrate compressed format for videoconferencing. It was developed by the ITU-T Video Coding Experts Group in a project ending in 1995/1996 as one member of the H.26x family of video coding standards in the domain of the ITU-T.H.263...
, include:
- Support for "MPEG"-style quantization
- Support for interlaced video
- Support for B pictures (a.k.a. B-frames)
- Quarter Pixel motion compensationMotion compensationMotion compensation is an algorithmic technique employed in the encoding of video data for video compression, for example in the generation of MPEG-2 files. Motion compensation describes a picture in terms of the transformation of a reference picture to the current picture. The reference picture...
(QpelQpelQuarter pixel refers to a quarter of a standard pixel. It is used in many modern video encoding standards such as MPEG-4 ASP and H.264/AVC to refer to quarter pixel precision in motion estimation and motion compensation...
) - Global motion compensationGlobal Motion CompensationGlobal motion compensation is a technique used in video compression to reduce the bitrate required to encode video. It is most commonly used in MPEG-4 ASP, such as with the DivX and Xvid codecs.-Operation:...
(GMC)
The MPEG quantization and interlace support are designed in basically similar ways to the way it is found in MPEG-2
MPEG-2
MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information". It describes a combination of lossy video compression and lossy audio data compression methods which permit storage and transmission of movies using currently available storage media and transmission...
Part 2. The B picture support is designed in a basically similar way to the way it is found in MPEG-2 Part 2 and H.263v2
H.263
H.263 is a video compression standard originally designed as a low-bitrate compressed format for videoconferencing. It was developed by the ITU-T Video Coding Experts Group in a project ending in 1995/1996 as one member of the H.26x family of video coding standards in the domain of the ITU-T.H.263...
.
The quarter-pixel motion compensation feature of ASP was innovative, and was later also included (in somewhat different forms) in MPEG-4 Part 10 and VC-1
VC-1
VC-1 is the informal name of the SMPTE 421M video codec standard, which was initially developed as a proprietary video format by Microsoft before it was released as a formal SMPTE standard video format on April 3, 2006...
. Some implementations omit support for this feature, because it has a significantly harmful effect on speed and it is not always beneficial for quality.
The global motion compensation feature is not actually supported in most implementations although the standard officially requires decoders to support it. Most encoders do not support it either, and some experts say that it does not ordinarily provide any benefit in compression. When used, ASP's global motion compensation has a large unfavorable impact on speed and adds considerable complexity to the implementation.
Criticisms
Despite being generally well received, MPEG-4 Part 2 has drawn some criticism. FFmpegFFmpeg
FFmpeg is a free software project that produces libraries and programs for handling multimedia data. The most notable parts of FFmpeg are libavcodec, an audio/video codec library used by several other projects, libavformat, an audio/video container mux and demux library, and the ffmpeg command line...
's maintainer Michael Niedermayer has criticised MPEG-4 for lacking an in-loop deblocking filter
Deblocking filter (video)
A deblocking filter is a video filter applied to blocks in decoded video to improve visual quality and prediction performance by smoothing the sharp edges which can form between macroblocks when block coding techniques are used...
, GMC being too computationally intensive, and OBMC being defined but not allowed in any profiles among other things. Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
's Ben Waggoner states "Microsoft (well before my time) went down the codec standard route before with MPEG-4 part 2, which turns out to be a profound disappointment across the industry - it didn't offer that much of a compression advantage over MPEG-2, and the protracted license agreement discussions scared off a lot of adoption. I was involved in many digital media projects that wouldn't even touch MPEG-4 in the late '90s to early '00s because there was going to be a 'content fee' that hadn't been fully defined yet."
Popular software implementations
- 3ivx3ivx3ivx is a video codec suite, created by 3ivx Technologies, based in Sydney, Australia, that allows the creation of MPEG-4 compliant data streams. It has been designed around a need for decreased processing power for use mainly in embedded systems. First versions were published in 2001...
- DivXDivXDivX is a brand name of products created by DivX, Inc. , including the DivX Codec which has become popular due to its ability to compress lengthy video segments into small sizes while maintaining relatively high visual quality.There are two DivX codecs; the regular MPEG-4 Part 2 DivX codec and the...
- HDX4HDX4HDX4 is an MPEG-4 codec developed by a German company named Jomigo Visual Technology.Benchmark tests of c't , issue 05/2005 and Doom9.org showed that it was the fastest codec among the ones tested, with the downside of a slightly lesser encoding efficiency...
- libavcodecLibavcodeclibavcodec is a free software/open source LGPL-licensed library of codecs for encoding and decoding video and audio data. Same name but incompatible libraries are provided from both FFmpeg project and Libav project....
- Nero DigitalNero DigitalNero Digital is a brand name applied to a suite of MPEG-4-compatible video and audio compression codecs developed by Nero AG of Germany and Ateme of France...
- QuickTimeQuickTimeQuickTime is an extensible proprietary multimedia framework developed by Apple Inc., capable of handling various formats of digital video, picture, sound, panoramic images, and interactivity. The classic version of QuickTime is available for Windows XP and later, as well as Mac OS X Leopard and...
- XvidXviDXvid is a video codec library following the MPEG-4 standard, specifically MPEG-4 Part 2 Advanced Simple Profile . It uses ASP features such as b-frames, global and quarter pixel motion compensation, lumi masking, trellis quantization, and H.263, MPEG and custom quantization matrices.Xvid is a...