MPEG-4标准：互动视频革命的关键技术

需积分: 13 43 浏览量更新于2024-07-19 收藏 1.51MB PDF 举报

身份认证购VIP最低享 7 折!

30元优惠券

MPEG-4标准是由国际标准化组织MPEG（Moving Picture Experts Group）制定的一个国际标准，该组织还开发了著名的MPEG-1和MPEG-2标准，后者极大地推动了交互式视频在CD-ROM、DVD和数字电视中的应用。MPEG-4的创建是全球数百名研究人员和工程师共同努力的结果，旨在提供更加高效和灵活的多媒体内容编码和传输技术。 MPEG-4标准于1998年10月最终确定，并在1999年初成为国际标准。其最初版本包含了对先前技术的完全兼容性扩展，称为MPEG-4 Version 2，这部分在1999年底冻结，以获得2000年初的正式国际标准地位。自那时以来，MPEG-4标准经历了多次扩展，包括对音视频编码的改进，如H.264/AVC（Advanced Video Coding），这些编码技术显著提高了数据压缩效率和图像质量，使得高清视频和流媒体服务成为可能。 MPEG-4标准的核心理念在于支持广泛的多媒体应用场景，包括但不限于视频会议、虚拟现实、交互式游戏、移动设备娱乐和数字版权管理。它采用了模块化设计，允许开发者选择适合特定应用需求的不同功能和技术组件，如高级音频编码、运动补偿、纹理压缩等。 MPEG-4不仅仅关注视频编码，还包括音频编码、多媒体对象描述和交互式内容的表示。它定义了一套统一的框架，使得不同设备和平台之间能够无缝地处理和交换多媒体数据。此外，MPEG-4也注重内容的创作工具和用户界面设计，支持多媒体内容的创建、编辑和分发。随着技术的发展，MPEG-4标准还在不断演进，以适应新兴的互联网和物联网环境，例如通过扩展对WebRTC（Real-Time Communication）的支持，使得实时通信在远程教育、在线协作等领域得到广泛应用。尽管工作仍在进行中，但MPEG-4已经成为了多媒体领域不可或缺的一部分，为现代通信和娱乐技术奠定了坚实的基础。

资源详情

资源推荐

MPEG-4 Overview © MPEG 1999-2002 – unlimited reproduction permitted if not modified 13

The subsections below give an itemized overview of functionalities that the tools and

algorithms of in the MPEG-4 visual standard.

3.5.1 Formats Supported

The following formats and bitrates are be supported by MPEG-4 Visual :

 bitrates: typically between 5 kbit/s and more than 1 Gbit/s

 Formats: progressive as well as interlaced video

 Resolutions: typically from sub-QCIF to 'Studio' resolutions (4k x 4k pixels)

3.5.2 Compression Efficiency

 For all bit rates addressed, the algorithms are very efficient. This includes the compact

coding of textures with a quality adjustable between "acceptable" for very high

compression ratios up to "near lossless".

 Efficient compression of textures for texture mapping on 2-D and 3-D meshes.

 Random access of video to allow functionalities such as pause, fast forward and fast

reverse of stored video.

3.5.3 Content-Based Functionalities

 Content-based coding of images and video allows separate decoding and reconstruction of

arbitrarily shaped video objects.

 Random access of content in video sequences allows functionalities such as pause, fast

forward and fast reverse of stored video objects.

 Extended manipulation of content in video sequences allows functionalities such as

warping of synthetic or natural text, textures, image and video overlays on reconstructed

video content. An example is the mapping of text in front of a moving video object where

the text moves coherently with the object.

3.5.4 Scalability of Textures, Images and Video

 Complexity scalability in the encoder allows encoders of different complexity to generate

valid and meaningful bitstreams for a given texture, image or video.

 Complexity scalability in the decoder allows a given texture, image or video bitstream to

be decoded by decoders of different levels of complexity. The reconstructed quality, in

general, is related to the complexity of the decoder used. This may entail that less powerful

decoders decode only a part of the bitstream.

 Spatial scalability allows decoders to decode a subset of the total bitstream generated by

the encoder to reconstruct and display textures, images and video objects at reduced spatial

resolution. A maximum of 11 levels of spatial scalability are supported in so-called 'fine-

granularity scalability', for video as well as textures and still images.

 Temporal scalability allows decoders to decode a subset of the total bitstream generated by

the encoder to reconstruct and display video at reduced temporal resolution. A maximum

of three levels are supported.

 Quality scalability allows a bitstream to be parsed into a number of bitstream layers of

different bitrate such that the combination of a subset of the layers can still be decoded into

a meaningful signal. The bitstream parsing can occur either during transmission or in the

decoder. The reconstructed quality, in general, is related to the number of layers used for

decoding and reconstruction.

 Fine Grain Scalability – a combination of the above in fine grain steps, up to 11 steps

MPEG-4 Overview © MPEG 1999-2002 – unlimited reproduction permitted if not modified 14

3.5.5 Shape and Alpha Channel Coding

 Shape coding assists the description and composition of conventional images and video as

well as arbitrarily shaped video objects. Applications that benefit from binary shape maps

with images are content-based image representations for image databases, interactive

games, surveillance, and animation. There is an efficient technique to code binary shapes.

A binary alpha map defines whether or not a pixel belongs to an object. It can be ‘on’ or

‘off’.

 ‘Gray Scale’ or ‘alpha’ Shape Coding

An alpha plane defines the ‘transparency’ of an object, which is not necessarily uniform; it

can vary over the object, so that, e.g., edges are more transparent (a technique called

feathering). Multilevel alpha maps are frequently used to blend different layers of image

sequences. Other applications that benefit from associated binary alpha maps with images

are content-based image representations for image databases, interactive games,

surveillance, and animation.

3.5.6 Robustness in Error Prone Environments

Error resilience allows accessing image and video over a wide range of storage and

transmission media. This includes the useful operation of image and video compression

algorithms in error-prone environments at low bit-rates (i.e., less than 64 Kbps). There are tools

that address both the band-limited nature and error resiliency aspects of access over wireless

networks.

3.5.7 Face and Body Animation

The ‘Face and Body Animation’ tools in the standard allow sending parameters that can define,

calibrate and animate synthetic faces and bodies. These models themselves are not

standardized by MPEG-4, only the parameters are, although there is a way to send, e.g., a well-

defined face to a decoder.

The tools include:

 Definition and coding of face and body animation parameters (model independent):

 Feature point positions and orientations to animate the face and body definition meshes

 Visemes, or visual lip configurations equivalent to speech phonemes

 Definition and coding of face and body definition parameters (for model calibration):

 3-D feature point positions

 3-D head calibration meshes for animation

 Personal characteristics

 Facial texture coding

3.5.8 Coding of 2-D Meshes with Implicit Structure

2D mesh coding includes:

 Mesh-based prediction and animated texture transfiguration

 2-D Delaunay or regular mesh formalism with motion tracking of animated objects

 Motion prediction and suspended texture transmission with dynamic meshes.

 Geometry compression for motion vectors:

 2-D mesh compression with implicit structure & decoder reconstruction

3.5.9 Coding of 3-D Polygonal Meshes

MPEG-4 provides a suite of tools for coding 3-D polygonal meshes. Polygonal meshes are

widely used as a generic representation of 3-D objects. The underlying technologies compress

MPEG-4 Overview © MPEG 1999-2002 – unlimited reproduction permitted if not modified 15

the connectivity, geometry, and properties such as shading normals, colors and texture

coordinates of 3-D polygonal meshes.

The Animation Framework eXtension (AFX, see further down) will provide more elaborate

tools for 2D and 3D synthetic objects.

4 Extensions Underway

MPEG is currently working on a number of extensions:

4.1.1 New Video codec: "MPEG-4 Advanced Video Coding"

Work is ongoing on MPEG-4 part 10, 'Advanced Video Coding', This codec is being developed

jointly with ITU-T, in the so-called Joint Video Team (JVT). The JVT unites the standard

world's video coding experts in a single group. The work currently underway is based on

earlier work in ITU-T on 'H.26L'. H.26L and MPEG-4 part 10 will be the same. (H.26L will be

renamed when it is done. The final name may be H.264, but that is not yet sure). MPEG-4

AVC/H.26L is slated to be ready by the end of 2002.

4.1.2 The Animation Framework eXtension, AFX

The Animation Framework extension (AFX – pronounced ‘effects’) provides an integrated

toolbox for building attractive and powerful synthetic MPEG-4 environments. The framework

defines a collection of interoperable tool categories that collaborate to produce a reusable

architecture for interactive animated contents. In the context of AFX, a tool represents

functionality such as a BIFS node, a synthetic stream, or an audio-visual stream.

AFX utilizes and enhances existing MPEG-4 tools, while keeping backward-compatibility, by

offering:

 Higher-level descriptions of animations (e.g. inverse kinematics)

 Enhanced rendering (e.g. multi-texturing, procedural texturing)

 Compact representations (e.g. piecewise curve interpolators, subdivision surfaces)

 Low bitrate animations (e.g. using interpolator compression and dead-reckoning)

 Scalability based on terminal capabilities (e.g. parametric surfaces tessellation)

 Interactivity at user level, scene level, and client-server session level

 Compression of representations for static and dynamic tools

Compression of animated paths and animated models is required for improving the

transmission and storage efficiency of representations for dynamic and static tools.

4.1.3 Audio extensions

There are two work items underway for improving audio coding efficiency even further.

a) Bandwidth extension

Bandwidth extension is a tool that gives a better quality perception over the existing audio

signal, while keeping the existing signal backward compatible.

MPEG is investigating bandwidth extensions, and may standardize of one or both of:

1. General audio signals, to extend the capabilities currently provided by MPEG-4

general audio coders.

2. Speech signals, to extend the capabilities currently provided by MPEG-4 speech coders.

A single technology that addresses both of these signals is preferred. This technology shall be

both forward and backward compatible with existing MPEG-4 technology. In other words, an

MPEG-4 decoder can decode an enhanced stream and a new technology decoder can decode an

MPEG-4 stream. There are two possible configurations for the enhanced stream: MPEG-4

AAC streams can carry the enhancement information in the DataStreamElement, while all

MPEG-4 systems know the concept of elementary streams, which allow second Elementary

Stream for a given audio object, containing the enhancement information.

b) Parametric coding

The MPEG-4 standard already provides a parametric coding scheme for coding of general

audio signals for low bit-rates (HILN, "Harmonic Individual Lines and Noise"). The extension

investigates parametric coding of general audio signals for the higher quality range, to extend

the capabilities currently provided by HILN. Whenever possible this technology will build

upon the existing MPEG-4 HILN technology.

5 Profiles in MPEG-4

MPEG-4 provides a large and rich set of tools for the coding of audio-visual objects. In order

to allow effective implementations of the standard, subsets of the MPEG-4 Systems, Visual,

and Audio tool sets have been identified, that can be used for specific applications. These

subsets, called ‘Profiles’, limit the tool set a decoder has to implement. For each of these

Profiles, one or more Levels have been set, restricting the computational complexity. The

approach is similar to MPEG-2, where the most well known Profile/Level combination is

‘Main Profile @ Main Level’. A Profile@Level combination allows:

 a codec builder to implement only the subset of the standard he needs, while maintaining

interworking with other MPEG-4 devices built to the same combination, and

 checking whether MPEG-4 devices comply with the standard (‘conformance testing’).

Profiles exist for various types of media content (audio, visual, and graphics) and for scene

descriptions. MPEG does not prescribe or advise combinations of these Profiles, but care has

been taken that good matches exist between the different areas.

5.1 Visual Profiles

The visual part of the standard provides profiles for the coding of natural, synthetic, and

synthetic/natural hybrid visual content. There are five profiles for natural video content:

1. The Simple Visual Profile provides efficient, error resilient coding of rectangular video

objects, suitable for applications on mobile networks, such as PCS and IMT2000.

2. The Simple Scalable Visual Profile adds support for coding of temporal and spatial

scalable objects to the Simple Visual Profile, It is useful for applications which provide

services at more than one level of quality due to bit-rate or decoder resource limitations,

such as Internet use and software decoding.

3. The Core Visual Profile adds support for coding of arbitrary-shaped and temporally

scalable objects to the Simple Visual Profile. It is useful for applications such as those

providing relatively simple content-interactivity (Internet multimedia applications).

4. The Main Visual Profile adds support for coding of interlaced, semi-transparent, and

sprite objects to the Core Visual Profile. It is useful for interactive and entertainment-

quality broadcast and DVD applications.

剩余77页未读，继续阅读

同心圆的故事

粉丝: 5
资源: 8

MPEG-4标准：互动视频革命的关键技术

MPEG-4编码库

mpeg-2 简体中文

MPEG4(ASP)文件

Overview of the MPEG-4 Standard

mpeg-7 standard

Overview of the MPEG-7 Standard

Video coding using the H.264 MPEG-4 AVC compression standard

Video coding using the H.264/MPEG-4 AVC compression standard

Guide to MPEG-1 Audio Standard.pdf

The MPEG-7 Visual Standard for Content Description—An Overview

ISO/IEC 13818-1 MPEG-2 System Standard: Complete Overview and Components

the MPEG-4 Book

Video_coding_using_the_H.264_MPEG-4_AVC_compression_standard

ISO_IEC_14496-3_1998 MPEG-4 Audio

DynaGuard 216系列 全功能 MPEG-4 DVR 使用手册.pdf

H.264.And.MPEG-4.Video.Compression.Video.Coding.For.Next.Generation.Multimedia

最新资源

DynaGuard 216系列全功能 MPEG-4 DVR 使用手册.pdf