1 560 IEEE TRANSACTIONS ON Circuits AND SYSTEMS FOR video TECHNOLOGY, VOL. 13, NO. 7, JULY 2003. Overview of the video coding standard Thomas Wiegand, Gary J. Sullivan, Senior Member, IEEE, Gisle Bj ntegaard, and Ajay Luthra, Senior Member, IEEE. Abstract is newest video coding standard of the ITU-T video coding Experts Group and the ISO/IEC Moving Picture Experts Group. The main goals of the stan- dardization effort have been enhanced compression performance and provision of a network-friendly video representation addressing conversational ( video telephony) and noncon- versational (storage, broadcast, or streaming) applications. Fig. 1. Scope of video coding standardization.
2 Has achieved a significant improvement in rate-distor- tion efficiency relative to existing standards . This article provides an Overview of the technical features of , describes and has diversified from ISDN and T1/E1 service to embrace profiles and applications for the standard , and outlines the history PSTN, mobile wireless networks, and LAN/Internet network of the standardization process. delivery. Throughout this evolution, continued efforts have Index Terms AVC, , , JVT, MPEG-2, MPEG-4, been made to maximize coding efficiency while dealing with standards , video . the diversification of network types and their characteristic formatting and loss/error robustness requirements.
3 Recently the MPEG-4 Visual (MPEG-4 part 2) standard . I. INTRODUCTION. has also begun to emerge in use in some application domains of H .264/AVC is the newest international video coding stan- dard . By the time of this publication, it is expected to have been approved by ITU-T as Recommendation and the prior coding standards . It has provided video shape coding capability, and has similarly worked toward broadening the range of environments for digital video use. by ISO/IEC as International standard 14 496 10 (MPEG-4 part In early 1998, the video coding Experts Group (VCEG). 10) Advanced video coding (AVC). ITU-T SG16 issued a call for proposals on a project called The MPEG-2 video coding standard (also known as ITU-T , with the target to double the coding efficiency (which ) , which was developed about ten years ago primarily means halving the bit rate necessary for a given level of fidelity).
4 As an extension of prior MPEG-1 video capability with support in comparison to any other existing video coding standards for of interlaced video coding , was an enabling technology for dig- a broad variety of applications. The first draft design for that ital television systems worldwide. It is widely used for the trans- new standard was adopted in October of 1999. In December of mission of standard definition (SD) and high definition (HD) 2001, VCEG and the Moving Picture Experts Group (MPEG). TV signals over satellite, cable, and terrestrial emission and the ISO/IEC JTC 1/SC 29/WG 11 formed a Joint video Team storage of high-quality SD video signals onto DVDs. (JVT), with the charter to finalize the draft new video coding However, an increasing number of services and growing standard for formal approval submission as  in popularity of high definition TV are creating greater needs March 2003.
5 For higher coding efficiency. Moreover, other transmission The scope of the standardization is illustrated in Fig. 1, which media such as Cable Modem, xDSL, or UMTS offer much shows the typical video coding /decoding chain (excluding the lower data rates than broadcast channels, and enhanced coding transport or storage of the video signal). As has been the case efficiency can enable the transmission of more video channels for all ITU-T and ISO/IEC video coding standards , only the or higher quality video representations within existing digital central decoder is standardized, by imposing restrictions on the transmission capacities. bitstream and syntax, and defining the decoding process of the video coding for telecommunication applications has syntax elements such that every decoder conforming to the stan- evolved through the development of the ITU-T , dard will produce similar output when given an encoded bit- (MPEG-2), and video coding standards (and later stream that conforms to the constraints of the standard .)
6 This lim- enhancements of known as and ), itation of the scope of the standard permits maximal freedom to optimize implementations in a manner appropriate to spe- cific applications (balancing compression quality, implementa- Manuscript received April 15, 2002; revised May 10, 2003. T. Wiegand is with the Fraunhofer-Institute for Telecommunications, tion cost, time to market, etc.). However, it provides no guaran- Heinrich-Hertz-Institute, Einsteinufer 37, 10587 Berlin, Germany (e-mail: tees of end-to-end reproduction quality, as it allows even crude encoding techniques to be considered conforming. G. J. Sullivan is with the Microsoft Corporation, Redmond, WA 98052 USA.
7 (e-mail: This paper is organized as follows. Section II provides a high- G. Bj ntegaard is with the Tandberg, N-1324 Lysaker, Norway (e-mail: level Overview of applications and highlights some key technical features of the design that enable improved oper- A. Luthra is with the Broadband Communications Sector, Motorola, Inc., San Diego, CA 92121 USA. (e-mail: ation for this broad variety of applications. Section III explains Digital Object Identifier the network abstraction layer (NAL) and the overall structure 1051-8215/03$ 2003 IEEE. WIEGAND et al.: Overview OF THE video coding standard 561. dard, but further reduces the complexity of the interpola- tion processing compared to the prior design.)))
8 Motion vectors over picture boundaries: While motion vectors in MPEG-2 and its predecessors were required to point only to areas within the previously-decoded refer- ence picture, the picture boundary extrapolation technique first found as an optional feature in is included in Multiple reference picture motion compensation: Pre- dictively coded pictures (called P pictures) in MPEG-2. and its predecessors used only one previous picture to pre- Fig. 2. Structure of video encoder. dict the values in an incoming picture. The new design ex- tends upon the enhanced reference picture selection tech- of coded video data. The video coding layer (VCL) nique found in to enable efficient coding by al- is described in Section IV.
9 Section V explains the profiles sup- lowing an encoder to select, for motion compensation pur- ported by and some potential application areas of poses, among a larger number of pictures that have been the standard . decoded and stored in the decoder. The same extension of referencing capability is also applied to motion-com- pensated bi-prediction, which is restricted in MPEG-2 to II. APPLICATIONS AND DESIGN FEATURE HIGHLIGHTS using two specific pictures only (one of these being the The new standard is designed for technical solutions in- previous intra (I) or P picture in display order and the other cluding at least the following application areas being the next I or P picture in display order).
10 Decoupling of referencing order from display order: Broadcast over cable, satellite, cable modem, DSL, terres- In prior standards , there was a strict dependency between trial, etc. the ordering of pictures for motion compensation refer- Interactive or serial storage on optical and magnetic de- encing purposes and the ordering of pictures for display vices, DVD, etc. purposes. In , these restrictions are largely re- Conversational services over ISDN, Ethernet, LAN, DSL, moved, allowing the encoder to choose the ordering of wireless and mobile networks, modems, etc. or mixtures pictures for referencing and display purposes with a high of these. degree of flexibility constrained only by a total memory video -on-demand or multimedia streaming services over capacity bound imposed to ensure decoding ability.