MPEG-4 Part 2, MPEG-4 Visual (formally ISO/IEC 14496-2^[1]) 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 codecs including DivX, Xvid and Nero Digital implement this standard.

Note that MPEG-4 Part 10 defines a different format from 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.)^[2][3][4] 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).^[5] MPEG-4 Part 2 is partially based on ITU-T H.263.^[6] The first MPEG-4 Video Verification Model (simulation and test model) used ITU-T H.263 coding tools together with shape coding.^[7]

Editions[link]

Profiles[link]

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 (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.

Simple Profile (SP)[link]

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 phones, some low end video conferencing systems, electronic surveillance systems etc.

Advanced Simple Profile (ASP)[link]

Advanced Simple Profile 's notable technical features relative to the Simple Profile, which is roughly similar to H.263, include:

• Support for "MPEG"-style quantization
• Support for interlaced video
• Support for B pictures (a.k.a. B-frames)
• Quarter Pixel motion compensation (Qpel)
• Global motion compensation (GMC)

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.

Criticisms[link]

Despite being generally well received, MPEG-4 Part 2 has drawn some criticism. FFmpeg'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.^[11] 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."^[12]

Popular software implementations[link]

• 3ivx
• DivX
• HDX4
• libavcodec
• Nero Digital
• QuickTime
• Xvid

See also[link]

• Quantization (image processing)
• FourCC
• MP3

Notes[link]

External links[link]

• MPEG-4 Part 2: Visual
• Levels for MPEG-4 Visual Profiles
• Official MPEG web site

Part Two, Part 2 or Part II may refer to:

• Part Two (Throbbing Gristle album), 2007
• Part 2 (Wayne Wonder & Sanchez album), 1991
• Part II (Brad Paisley album), 2001
• Part II (Lil Jon & the East Side Boyz album), 2003

This disambiguation page lists articles associated with the same title. If an internal link led you here, you may wish to change the link to point directly to the intended article.

MPEG-4 is a method of defining compression of audio and visual (AV) 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 (MPEG) (ISO/IEC JTC1/SC29/WG11) under the formal standard ISO/IEC 14496 – Coding of audio-visual objects. Uses of MPEG-4 include compression of AV data for web (streaming media) and CD distribution, voice (telephone, videophone) and broadcast television applications.

Background[link]

MPEG-4 absorbs many of the features of MPEG-1 and MPEG-2 and other related standards, adding new features such as (extended) VRML support for 3D rendering, object-oriented composite files (including audio, video and VRML objects), support for externally-specified Digital Rights Management and various types of interactivity. AAC (Advanced Audio Coding) was standardized as an adjunct to MPEG-2 (as Part 7) before MPEG-4 was issued.

MPEG-4 is still a developing standard and is divided into a number of parts. Companies promoting MPEG-4 compatibility do not always clearly state which "part" level compatibility they are referring to. The key parts to be aware of are MPEG-4 part 2 (including Advanced Simple Profile, used by codecs such as DivX, Xvid, Nero Digital and 3ivx and by Quicktime 6) and MPEG-4 part 10 (MPEG-4 AVC/H.264 or Advanced Video Coding, used by the x264 encoder, by Nero Digital AVC, by Quicktime 7, and by high-definition video media like Blu-ray Disc).

Most of the features included in MPEG-4 are left to individual developers to decide whether to implement them. This means that there are probably no complete implementations of the entire MPEG-4 set of standards. To deal with this, the standard includes the concept of "profiles" and "levels", allowing a specific set of capabilities to be defined in a manner appropriate for a subset of applications.

Initially, MPEG-4 was aimed primarily at low bit-rate video communications; however, its scope as a multimedia coding standard was later expanded. MPEG-4 is efficient across a variety of bit-rates ranging from a few kilobits per second to tens of megabits per second. MPEG-4 provides the following functions:

• Improved coding efficiency over MPEG-2^{[citation needed]}
• Ability to encode mixed media data (video, audio, speech)
• Error resilience to enable robust transmission
• Ability to interact with the audio-visual scene generated at the receiver

Overview[link]

MPEG-4 provides a series of technologies for developers, for various service-providers and for end users:

• MPEG-4 enables different software and hardware developers to create multimedia objects possessing better abilities of adaptability and flexibility to improve the quality of such services and technologies as digital television, animation graphics, the World Wide Web and their extensions.
• Data network providers can use MPEG-4 for data transparency. With the help of standard procedures, MPEG-4 data can be interpreted and transformed into other signal types compatible with any available network.
• The MPEG-4 format provides end users with a wide range of interaction with various animated objects.
• Standardized Digital Rights Management signaling, otherwise known in the MPEG community as Intellectual Property Management and Protection (IPMP).

The MPEG-4 format can perform various functions, among which might be the following:

• Multiplexes and synchronizes data, associated with media objects, in such a way that they can be efficiently transported further via network channels.
• Interaction with the audio-visual scene, which is formed on the side of the receiver.

Profiles and Levels[link]

MPEG-4 provides a large and rich set of tools for encoding. Subsets of the MPEG-4 tool sets have been provided for use in specific applications. These subsets, called 'Profiles', limit the size of the tool set a decoder is required to implement.^[1] In order to restrict computational complexity, one or more 'Levels' are set for each Profile.^[1] A Profile and Level combination allows:^[1]

• A codec builder to implement only the subset of the standard needed, while maintaining interworking with other MPEG-4 devices that implement the same combination.^[1]
• Checking whether MPEG-4 devices comply with the standard, referred to as conformance testing.^[1]

MPEG-4 parts[link]

MPEG-4 consists of several standards—termed "parts"—including the following (each part covers a certain aspect of the whole specification):

Profiles are also defined within the individual "parts", so an implementation of a part is ordinarily not an implementation of an entire part.

MPEG-1, MPEG-2, MPEG-7 and MPEG-21 are other suites of MPEG standards.

MPEG4 Levels[link]

Licensing[link]

MPEG-4 contains patented technologies which use requires licensing in countries that acknowledge software algorithm patents. Patents covering MPEG-4 are claimed by over two dozen companies. The MPEG Licensing Authority^[61] licenses patents required for MPEG-4 Part 2 Visual from a wide range of companies (audio is licensed separately) and lists all of its licensors and licensees on the site. New licenses for MPEG-4 System patents are under development^[62] and no new licenses are being offered while holders of its old MPEG-4 Systems license are still covered under the terms of that license for the patents listed (MPEG LA – Patent List).

AT&T is trying to sue companies such as Apple Inc. over alleged MPEG-4 patent infringement.^[63] The terms of Apple's Quicktime 7 license for users^[64] describes in paragraph 14 the terms under Apple's existing MPEG-4 System Patent Portfolio license from MPEGLA.

See also[link]

• MPEG
• MPEG-4 Structured Audio
• MPEG-4 SLS

References[link]

External links[link]

• Overview of the MPEG-4 Standard at the MPEG Official Website
• MPEG-4: The container for digital media^{[dead link]}
• AAC at core of MPEG-4, 3GPP and 3GPP2 specifications
• MPEG Industry Forum (MPEGIF) MPEG-4 page
• MPEG Industry Forum (MPEGIF) MPEG-4 White Paper
• JM MPEG-4 AVC /H.264 Reference Code
• OpenIPMP: Open Source DRM Project for MPEG-4