In this book, we start by reviewing briefly the basics of video, including scanning, formation of colour components at various video formats and quality evaluation of video. At the end of each chapter, a few problems have been designed, either to cover some specific parts of the book in greater depth or for a better appreciation of those parts. Principles of video compression techniques used in the standard codecs are given in Chapter 3. These include the three fundamental elements of compression: spatial, temporal and intersymbol redundancy reductions. The DCT, as the core element of all the standard codecs, and its fast implementation is presented. Quantisation of the DCT coefficients for bit rate reduction is given. The most important element of temporal redundancy reduction, namely motion compensation, is discussed in this chapter. Two variable length coding techniques for reduction of the entropy of the symbols, namely, Huffman and arithmetic coding, are described. Special attention is paid on the arithmetic coding, because of its role and importance in recent video codecs. The chapter ends with an overview of a generic interframe video codec, which is used as a generic codec in the following chapters to describe various standard codecs.

The statistical analysis of video signals indicates that there is a strong correlation both between successive picture frames and within the picture elements themselves. Theoretically, decorrelation of these signals can lead to bandwidth compression without significantly affecting image resolution. Moreover, the insensitivity of the human visual system to loss of certain spatio-temporal visual information can be exploited for further reduction. Hence, subjectively lossy compression techniques can be used to reduce video bit rates while maintaining an acceptable image quality. For coding still images, only the spatial correlation is exploited. Such a coding technique is called intraframe coding and is the basis for Joint Photographic Experts Group (JPEG) coding. If temporal correlation is exploited as well, then it is called interframe coding. Interframe predictive coding is the main coding principle that is used in all standard video codecs, such as H.261, H.263, H.264 and Motion Picture Experts Group (MPEG)-l, -2 and -4.

In the mid-1980s, joint work by the members of the International Tele communication Union (Telegraphy section) (ITU-T) and the International Standards Organisation (ISO) led to a standardisation for compression of greyscale and colour still images [1]. This effort was then known as the Joint Photographic Experts Group (JPEG). As it is apparent, the word joint refers to the collaboration between the ITU-T and ISO. The JPEG encoder is capable of coding full colour images at an average compression ratio of 15:1 for subjectively transparent quality [2]. Its design meets special constraints, which make the standard very flexible. For example, the JPEG encoder is parametrizable so that the desired compression/ quality trade-offs can be determined based on the application or the wishes of the user [3]. JPEG can also be used in coding of video, on the basis that video is a succession of still images. In this case, the process is called motion JPEG. Currently, motion JPEG has found numerous applications. The most notable one is video coding for transmission over packet networks with unspecified bandwidth or bit rates (UBR). A good example of UBR networks is the Internet where, because of unpredictability of the network load, congestion may last for a significant amount of time. Since in motion JPEG, each frame is independently coded, it is an ideal encoder of video for such a hostile environment.

MPEG-l is the first generation of video codecs proposed by the Motion Picture Experts Group (MPEG) as a standard to provide video coding for digital storage media (DSM), such as compact disc (CD), digital audio tape (DAT), Winchester discs and optical drives. This development was in response to industry needs for an efficient way of storing visual information on storage media other than the conventional ana logue video cassette recorders (VCRs). At the time the CD-ROMs had the capability of 648 Mbytes, sufficient to accommodate movie programmes at a rate of approximately 1.2 Mbit/s, and the MPEG standard aimed to conform roughly to this target. Although in most applications the MPEG-l video bit rate is in the range of 1-1.5 Mbit/s, the international standard does not limit the bit rate, and higher bit rates might be used for other applications.

The H.263 recommendation specifies a coded representation that can be used for compressing the moving picture components of audio-visual services at low bit rates. Detailed specifications of the first generation of this codec under the test model (TM) to verify the performance and compliance of this codec were finalised in 1995. The basic configuration of the video source algorithm in this codec is based on the ITU-T recommendation H.261, which is a hybrid of inter picture prediction to utilise temporal redundancy and transform coding of the residual signal to reduce spatial redundancy. However, during the course of the development of H.261 and the subsequent advances on video coding in MPEG-1 and -2 video codecs, substantial experience was gained, which has been exploited to make H.263 an efficient encoder. In this chapter, those parts of the H.263 standard that make this codec more efficient than its predecessors are explained.

The ITU-T video coding experts group, after successful completion of their H.263 video codec in 1995, started to work on the advanced video coding (AVC) project. Their long-term objective was to recommend a video codec to be at least twice better than the existing video codec, such as H.263. The project was initially called H.26L, with L standing for long-term objectives [1]. However, H.263 was under constant improvement. Its improved version under H.263+ was finalised in 1997, and in 2000, the H.263H-\specification was ratified, where each + is an indication of major improvement. Most of the innovations in H.263+ in the forms of options or annexes were also fed to H.26L. ITU-T submitted H.26L to MPEG call for proposals in 2001. MPEG-4 experts group of ISO/IEC, who were not very happy with their content-based video codec (due to high complexity the codec could not be marketed), and its frame-based counterpart had a similar performance to H.263, showed an interest in this new codec. They joined the AVC project and worked closely with the ITU-T team. The project's name was then changed to joint video team (JVT).

This appendix tackles the C program for the fast discrete cosine transform.

This appendix discusses the Huffman tables for quad tree shape coding: table_012.dat is used at levels 0,1 and 2 and table_3.dat is used at level 3.

This appendix talks about the channel error and packet loss modelling.

This appendix provides a glossary of acronyms.