MPEG-4 Introduction MPEG 4 Video MPEG 4 Tools

MPEG-4 –Introduction –MPEG 4 Video –MPEG 4 Tools –MPEG 4 Video Object –MPEG 4 Video Profile –MPEG 4 Simple Profile –MPEG 4 Advanced Simple Prolile

Introduction • ITU/ISO 1994年制定，1998年成为标准，对应的标准 号为 14496 • 目的是要在异构网络环境下能够高度可靠地 作，并 且具有很强的交互功能。 • 制定了一个称为传输多媒体集成框架(Delivery Multimedia Integration Framework，DMIF)的会话协议， 它用来管理多媒体数据流 ，DMIF覆盖了三种主要技术： – 广播技术 – 交互网络技术 – 光盘技术 • 相对其他编码标准，引入了对象的概念，以对象为编 码单位，有自然数据扩展到合成数据，对象可以是自 然的，也可以计算机合成的，可以是图像，也可以是 声音，可以是一段文字，总之对象是一个抽象的概念，

MPEG－4标准的16个部分 Part 1, Systems: Scene description, multiplexing of audio, video and related information, synchronisation, buffer management, intellectual property management. Part 2, Visual: Coding of ‘natural’ and ‘synthetic’ visual objects (see Chapter 5). Part 3, Audio: Coding of natural and synthetic audio objects. Part 4, Conformance Testing: Conformance conditions, test procedures, test bitstreams. Part 5, Reference Software: Publicly-available software that implements most tools in the standard. Part 6, Delivery Multimedia Integration Framework: Asession protocol for multimedia streaming. Part 7, Optimised Visual Reference Software: Optimised software implementation of selected Visual coding tools. This Part is a Technical Report (and not an International Standard).

MPEG－4标准的16个部分 Part 8, Carriage of MPEG-4 over IP: Specifies the mechanism for carrying MPEG-4 coded data over Internet Protocol (IP) networks. Part 9, Reference Hardware Description: VHDL descriptions of MPEG 4 coding tools (suitable for implementation in ICs). This Part is a Technical Report and is still under development. Part 10, Advanced Video Coding: Efficient coding of natural video (see Chapter 6). This Part is under development and due to become an International Standard in 2003. Part 11, Scene Description and Application Engine. Part 12, ISO Base Media File Format. Part 13, Intellectual Property Management and Protection Extensions. Part 14, MPEG-4 File Format Part 15, AVC File Format Part 16, Animation Framework Extension.

MPEG－4视频 和MPEG-1/-2 Video不同， MPEG 4视频形状 可以是矩形的也可以被分割成许多任意形状 的图 像区，每个区都有可能覆盖描述场 景中 感兴 趣的物理对 象或者内容，这 种区被定 义为图 像对 象区VOP。 VO的属性：形状，纹理，移动

MPEG 4中的Tools • A tool is a subset of coding functions to support a specific feature • 一些编码技术，比如DCT，帧内编码，前 向预测，双向预测….

MPEG 4中的视频对象 A entity that a user is allowed to access (seek, browse) and manipulate (cut and paste) A video object (VO) is an area of the video scene that may occupy an arbitrarily-shaped region and may exist for an arbitrary length of time.

Rectangular Video Object

Arbitrary shape Video Object

Video Scene

Profiles • A profile is a set of object types that a CODEC isexpected to be capable of handling. • Profile中明确了使用那些技术对那些对象进行编码

Profile of nature video

Profile of synthetic or hybrid video

Visual Profile and Visual Object Type

Levels

Simple Profile • Define Subset Tools for Simple Video Objects – I-VOP (Intra-coded rectangular VOP, progressive video format); – P-VOP (Inter-coded rectangular VOP, progressive video format); – short header (mode for compatibility with H. 263 CODECs); – compression efficiency tools (four motion vectors per macroblock, unrestricted motion vectors, Intra prediction); – transmission efficiency tools (video packets, Data Partitioning, Reversible Variable Length Codes).

Advanced Simple Profile • An Advanced Simple Profile. CODECmust be capable of decoding Simple objects as well as Advanced Simple objects which may use the following tools in addition to the Simple Profile tools –B-VOP (bidirectionally predicted Inter-coded VOP); –quarter-pixel motion compensation; –global motion compensation; –alternate quantiser; –interlace (tools for coding interlaced video sequences).

Tools of SP and ASP Visual Tools I-VOP P-VOP B-VOP DC Prediction AC Prediction 4 -MV, Unrestricted MV Slice Resynchronization Data Partitioning Reversible VLC Short Header Method 1/Method 2 Quantization Interlace Global Motion Compensation Quarter-pel Motion Compensation Visual Object Types Advanced Simple simple X X X X X X

图像的合成

Video Object

MPEG 4编码框图