This chapter discusses video coding. Digital video compression techniques have played an important role in the world of telecommunication and multimedia systems where bandwidth is still a valuable commodity. Hence, video coding techniques are of prime importance for reducing the amount of information needed for a picture sequence without losing much of its quality, judged by the human viewers.

This chapter discusses the principles of video compression. 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 with out 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.

In the mid 1980s joint work by the members of the ITU-T (International Telecommunication Union) and the ISO (International Standards Organisation) led to standardisation for the compression of grey scale and colour still images. This effort was then known as JPEG: the Joint Photographic Experts Group. As 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. Its design meets special constraints, which make the standard very flexible. For example, the JPEG encoder is parametrisable, so that the desired compression/quality trade-offs can be determined based on the application or the wishes of the user.

MPEG-1 is the first generation of video codecs proposed by the Motion Picture Experts Group as a standard to provide video coding for digital storage media (DSM), such as CD, 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 analogue video cassette recorders (VCR). At the time the CD-ROMs had the capability of 648 Mbytes, sufficient to accommodate movie programs at a rate of approximately 1.2Mbit/s, and the MPEG standard aimed to conform roughly with this target. Although in most applications the MPEG-1 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 ITU-T Recommendation H.261, which is a hybrid of interpicture 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 MPEG-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 will be explained.

This chapter discusses content description, search and delivery. In summary, MPEG-7 is about describing and finding contents and MPEG-21 deals with the delivery and consumption of these contents. As we see, none of these standards are about video compression, which is the main subject of this book. However, for the completeness of a book on the standard codecs we briefly describe these two new standards that incidentally are developed by the ISO/IEC MPEG standard bodies.

This appendix shows the Huffman tables for the DC and AC coefficients of the JPEG baseline encoder.

This appendix shows the frequency tables for intra and inter blocks, used in the context-based arithmetic encoding (CAE) method of binary shapes.

This appendix deals with various solutions of the problems given in all the chapters of the book. The book is based on standard codecs, image compression, video coding.