EBU • UER - Technical Review

EBU Technical Review : No. 276 (Summer 1998)

Broadcaster's guide to RDS

Scott Wright is a Member of the RDS Forum and the Chairman of the NRSC Subcommittee that standardized RBDS for North America. The name RBDS is used only for the North American standard to distinguish it clearly from the European CENELEC RDS standard which very recently has become an integral part of the RBDS standard. Products conforming to the RBDS standard will carry the RDS logo as in Europe and the consumer will encounter only RDS products. Scott Wright was instrumental in establishing these facts.

This being said, we have here a book from a competent leader in the field of RDS technology. Scott Wright is also a designer of Delco RDS car radio products, used by car manufacturers world-wide. With this book, he hopes to sell the advantages of RDS to the American FM broadcasters. So far, they have been reluctant to use RDS (only 700 FM stations out of 5000 have so far implemented RDS in the USA) because there have been very few commercial RDS products on the American market, in spite of the fact that in Europe more than 50 million RDS radios have been sold.

Scott Wright is convinced that RDS will also become a success in North America. He wants to give the necessary impetus to make this happen. This book thus aims to provide the necessary information to station owners, radio programme directors and salespersons about what RDS could do for their FM broadcast station and for their listeners.

The book is extremely well written. It is more addressed at the decision makers and not so much at the design engineers. The specifications described are those of the 1998 version of the RDS and RBDS standards. The differences between the two standards, although very small and subtle, are well explained. The book contains many examples of readily-available RDS products on the US market. It also demonstrates – to the US FM broadcasters and the receiver industry – how easy and inexpensive it is to implement RDS.

The Broadcaster's Guide to RDS
Scott Wright (Delco)
Bound volume of 203 pages
Focal Press, Oxford, UK, 1997
Ref: ISBN 0-240-80278-0. Price: £27.50.

Dietmar Kopitz

Video compression

There may never be a book that answers ALL the questions you were afraid to ask about video compression, but this one may come very close. Aimed at the video engineer working in the field, it explains simply and clearly both the current objectives and methods of video compression systems, and the systems of the future which will bombard the marketplace with this type of equipment.

After a general introduction to the subject and explanations of the basic techniques used for general data compression, the Author moves on to a more detailed examination of image compression and video compression. From his first-hand knowledge of the development firstly of JPEG and then MPEG, he is able to guide the reader through from the very origins of these two compression systems.

The book gives a background description of image structure, without which it is difficult to understand (i) how the redundancy of information can be exploited and (ii) the complexities of the many layers in MPEG. This leads the reader on to more detailed explanations of:

entropy coding, which sends the most common messages with the fewest bits;
differential coding, which exploits the predictability of the signal;
transforms, particularly the discrete cosine transform (DCT) which can separate the most vital information from the video signal and allow the least important information to be discarded if necessary;
and, finally, the choice of quantizing resolution by which bit-rate can be traded for noise.

Moving on from general techniques to particular systems, the Author looks in detail at the JPEG image compression which is used in almost all Non-Linear Editors currently on the market. Although it may now have been superseded by MPEG for the compression of true video, JPEG will probably be encountered for many more years in television production. Furthermore many of the techniques of JPEG, if not the parameter values, are used in the MPEG compression systems that have been developed. The effects of compression are well illustrated here and throughout the book by details taken from pictures before and after coding.

The major difference between JPEG and MPEG is that the latter exploits the temporal redundancy in video signals. How this is done and how successive images are analyzed to separate the movement from the random changes in the pictures is covered in a dedicated chapter. MPEG-1 was designed for the delivery of video at low bit-rates and it was only with the later MPEG-2 technology that systems that were suitable, firstly, for television delivery and, at a later stage, for television production were developed. Systems (in the plural) is the operative concept here because MPEG allows for many variants of its layers, and even the "profiles" which were chosen to cover the most likely uses are numbered in dozens.

MPEG-1 and MPEG-2 were designed to include the audio component of television, and the book explains how the coded video and audio signals are assembled into the complete "transport" datastream of a programme. The audio compression used in MPEG is covered but probably not in as much detail as an audio specialist would like.

The book concentrates on the JPEG and MPEG families of compression, which are open standards available from the ISO/IEC. However it does give due importance to (if not much detail on) other DCT systems which have been developed commercially, such as DV and SX. It also briefly describes the more esoteric proposals such as wavelet and fractal coding. Lastly, the Author covers the initial steps which are being taken in the process of exploiting MPEG for television delivery and production. But these developments are happening too quickly for the treatment to be anything other than a signposting towards the future.

If you are a broadcast television engineer and want an introduction to video compression, particularly MPEG, then this is the book for you. Even with the rapid developments taking place at the moment, it should also serve as a reference book on the basics of video compression for many years to come.

Video Compression
Peter D Symes
Hardbound volume of 322 pages
McGraw-Hill, 1998
Ref: ISBN 0-07-063344-4. Price:$55.00

Richard Chalmers

Telecommunications handbook

This German reference book describes the state of the art in telecommunications. About 70 key experts from the German telecommunications industry and specialized schools and research institutes have contributed to establish the six chapters. There are two chapters on fundamentals, one on service provision, one on networks, one on terminal equipment and one on regulatory aspects that, together, cover all the topics of modern technology in this field. Only basic knowledge is required from the reader. The book is laid out to give a pragmatic overview not only for engineers, but also for decision makers in service provision, marketing and distribution of products. This book is a competent assessment of present and future technologies in the fast-growing telecommunications sector. Many up-to-date figures and tables include forecasts beyond the year 2000 which illustrate well the facts presented.

From a broadcasting point-of-view, the book contains elements of the following technologies: video coding, video compression, video conferencing and communications, DVB and video-on-demand.

This well-written book however devotes greater detail to terrestrial and satellite telephone networking for fixed and mobile terminals, and it also includes good summaries of the relevant computer technologies used in this context. Established and up-coming ITU and ETSI standards are well referenced in the book.

Handbuch für die Telekommunikation (Handbook for Telecommunications)
Co-ordinating editors: V. Jung and H.-J. Warnecke
Hardbound volume of 888 pages
Springer Verlag, Berlin, 1998
Ref: ISBN 3-540-62631-X. Price: DM 198.

Dietmar Kopitz

DSP with computer applications

This is the second edition of what the publishers describe as "the essential introductory guide to Digital Signal Processing". The new edition features numerous updates which take account of the remarkable increase in the speed and power of computers over the last few years.

As with the first edition, the book comes with a considerable number of computer programs (both BASIC and PASCAL) on disk which serve to illustrate the text. These programs – which will run on most PC platforms – enable the reader to see the results of signal analysis and processing as the images build up on the computer screen.

After an introductory chapter on DSP, the book firstly deals with time-domain analysis, including convolution, then moves on to introduce digital Fourier techniques. The next chapter introduces the z-Transform and explains its relationship with the Fourier transform. Two chapters are then given over to some of the best-known techniques for designing nonrecursive and recursive digital filters, and are supported by a number of filter-design programs on the accompanying disk.

The aim of Chaper 7 is to give a clear introduction to a number of FFT topics – including "butterflies" and "twiddle factors" – which often cause a certain amount of consternation. This is followed by what is basically an applications chapter which shows how to use and interpret the results of FFT processing, including the rather difficult topic of spectral leakage.

Two new chapters in the second edition cover Random Digital Signals and Random DSP which are widely regarded as difficult topics. The Authors take a strictly introductory approach here in the belief that a clear understanding of the central ideas of the earlier chapters, extended to random phenomena, will stand readers in good stead for tackling the more advanced topics which they may encounter later. These two chapters are also well supported by the new and updated programs on the accompanying disk.

Altogether, this book provides an excellent and thorough introduction to DSP techniques.

Introductory Signal Processing with Computer Applications (2nd Edition)
P.A. Lynn and W. Fuerst
Bound volume of 479 pages
John Wiley and Sons, Chichester, UK, 1998
Ref: ISBN 0-471-97631-8. Price: £24.95.