EBU Technical Review : No. 277 (Autumn 1998)

Radio Data System

RDS has been one of the EBU's success stories. The first RDS specification was published by the EBU in 1984, after joint developments by several EBU Members in a spirit of mutual co-operation.

Two of the key players in the saga of RDS, Dietmar Kopitz and Bev Marks, have written this comprehensive book about RDS. As well as giving detailed explanations of "how" and "why" RDS works, it traces the history of RDS and its predecessors, such as the ARI system, and looks forward to new applications and services.

An early focus of RDS activities was to assist in the tuning of FM radios, especially in cars. Rather than displaying the frequency of the transmitter (which is of little relevance to the general public), RDS radios display the name of the radio service. Even better, RDS radios automatically re-tune to the best signal carrying the desired programme.

Amongst engineers, the features of RDS are known by a large number of abbreviations, such as PS (Programme Service name), PTY (Programme Type), AF (Alternative Frequency list) and ODA (Open Data Applications). Some RDS radios even have a button marked "TP" (which engineers will recognize as "Traffic Programme") but few consumers will understand what it does! This book explains all the features of RDS - including relatively new features such as DGPS.

The RDS specification has been revised several times since 1984:

An early, but very important, change to the original specification was that the ON (Other Networks) method of providing information about other networks was replaced by EON (Enhanced Other Networks). As this book states, the ON mechanism "just did not work!". On the basis that we may learn more from failures than from successes, it is unfortunate that the book provides no further explanation of this problem.

From the early days of RDS, it was clear that RDS could support a variety of additional data services, such as programme-related text services and paging. In recent years, broadcasting of Traffic and Travel Information has become increasingly important, especially for motorists. RDS-TMC was developed to deliver comprehensive information services without consuming large amounts of "air-time" for spoken announcements.

RDS-TMC was also conceived as a method of providing pan-European travel information services since it offered the prospect of a motorist being able to drive throughout Europe whilst hearing relevant traffic messages in his or her own language. This ambitious vision has not yet been realized, partly because voice synthesizers still leave a lot to be desired.

As indicated in this book, an even greater difficulty has been caused by the limited capacity of the RDS data channel. To overcome this problem, RDS-TMC uses a very efficient technique to compress data about traffic events, such as accidents or road closures. The short codes transmitted over the RDS channel are used in conjunction with location databases in each vehicle so that drivers can be given full information about traffic events. In general, the location databases for each country have been, or will be, prepared by national road authorities. It is expected that a modest handling charge will be made to cover the costs of replication and distribution, whether in the form of a smart card or a CD-ROM. However, some owners of national databases may try to recover the full costs of development from motorists, by limiting the use of the database to subscribers to the RDS-TMC services. In addition, there are also concerns about how the databases can be extended and maintained. It is clear that solving technical problems is easy compared with overcoming such institutional problems.

This book is lucid and well-written. I am sure that it will become a valuable reference source for all those involved in RDS. It is strongly recommended.

RDS: The Radio Data System
D. Kopitz and B. Marks
Hardbound volume of 300 pages
Artech House Books, London, 1998
Ref: ISBN 0-89006-744-9. Price £60.00

Phil Laven

Audio test signals

Many years ago, someone remarked that a true engineer would rather listen to "tone" than to any music yet composed. If that is so, then this must surely be their favourite CD. Although one of the most boring CDs ever made, it must also be one of the most useful to engineers working in broadcasting and other related branches of audio engineering.

Made under the supervision of Dr John Emmett, who has led and contributed to many EBU working groups over the years, almost all the recordings on the disk are sine-waves – of almost every imaginable combination of frequencies, levels and phases. These are, of course, test signals for audio equipment and meters of all sorts.

In the informative booklet that accompanies the CD, Dr Emmett leads us through the maze of standards which have been developed over the years by numerous national, international, professional and industry bodies who have tried to bring some order to the apparently simple task of finding and keeping an audio level.

A CD such as this is an ideal tool for providing a source of precision test signals. There is room for nearly 100 tracks so that the correct one can easily be identified and used for the task in hand. The CD does not seek to impose any solutions but, instead, contains examples of all known alignment levels as well as tracks that are suitable for use with all the programme meters in common use.

Briefly, the disk contains stereo tracks with:

• alignment levels and line-up signals;
• system test tracks;
• signals to test VU meters;
• signals to test three different variations of Peak Programme Meters (PPMs);
• signals to test phase meters;
• signals to test loudness meters;
• signals to check peak/RMS levels;
• pink noise;
• male speech.

This disk of course does not set out to replace such disks as the EBU SQAM or PEQS disks. These EBU disks contain music extracts and real sounds and are aimed at the subjective testing of systems and to give examples of quality of production.

The disk under review does however contain some of the same, or similar, signals to the Euroradio Measurements CD, EBU Tech 3270, but the EBU disk is designed for testing circuits as its name suggests.

International Broadcast Standards Tests is available as a DAT and MD as well as a CD.

International Broadcast Standards Test CD
Available on DAT, MD and CD
Canford Audio plc, 1998
http://www.canford.co.uk/

Richard Chalmers

The Tapeless Audio Directory - 7th Edition

The 6th Edition of the Tapeless Audio Directory was reviewed in EBU Technical Review No. 274, Winter 1997.

This edition follows the format of the earlier editions with the new features mentioned below. It contains over 500 entries, covering professional random- access audio systems intended for applications in radio and TV sound. These applications now include location recording, simple cart replacement, comprehensive editing and mixing, live play-out and fully automated systems for radio.

The stated aim of the guide is to help the potential purchaser establish what is on the market. The guide provides, where possible, full information on all important systems gained from questionnaires completed by manufacturers. This information covers target markets, hardware and software specifications, operational features, interfacing, networking and file transfer to external devices, archiving and backup systems. Also included is information on typical configurations and costs, on suppliers in Europe and elsewhere, and on training and support. Manufacturers' plans for future development are included with many of the entries.

In addition, the guide contains explanations of the terminology and offers advice to potential purchasers.

Where possible, this new edition of the guide indicates which hardware is required for any system; it indicates what is supplied as standard, what the user is required to supply, or what is optionally available. For editing systems, the guide now shows which processes are performed in real-time and which need to be rendered. It also now includes information on how systems interface with external devices, and how they can deal with the new longer word sizes and new digital formats.

For broadcast systems, more information is provided on how storage is supplied and organized, and how files are managed for library/database purposes, archiving and file transfer. An increasing number of systems now support BWF (Broadcast Wave Format), developed by the EBU, and the Directory shows which file formats are supported, and whether these can be read directly and/or imported/ exported.

This is a useful independent overview of the marketplace and could easily recover its cost by preventing fruitless telephone calls or, indeed, the purchase of inappropriate equipment.

The Tapeless Audio Directory (7th edition)
Bound volume of 104 pages
Sypha Publications, London, 1998
Ref: ISBN 1 901950 018. Price £19.95.

Richard Chalmers

Architectures for Digital Signal Processing

Architectures for Digital Signal Processing is an interesting technical guide to one of the key areas of modern circuit design. As processors become more powerful and the tasks they must perform become more varied, knowledge of the design of these DSPs becomes more important.

The book aims to bridge the gap between texts covering signal processing algorithms and those covering the implementation and design of micro- electronic circuits. There are large quantities of texts covering both these topics and indeed many university courses also make this split. It is a refreshing alternative to have a cross-disciplinary technical text such as this. Originally written by the author in German as a text book, it is geared in its revised and translated form as both a textbook and a reference for those working in the area. The language of the book is easy to follow and logical with certain residual characteristics from the original German text.

The book reviews basic digital circuit design techniques for VLSI (Very Large Scale Integrated) implementation in CMOS (Complimentary Metal-Oxide Semiconductor) technologies. Chapter 3 deals with circuit design techniques and architectures for implementing basic operations such as addition, subtraction, multiplication and division. General parallel processing and processor pipelining are dealt with in Chapter 4. Methods for mapping algorithms onto array processors are described in Chapter 5. These methods are particularly relevant to adapting architectures to implement regular algorithms.

One of the key applications of DSP design is in the areas of linear filter and discrete Fourier transform implementation, and these are discussed in Chapters 6 and 7. Chapter 8 deals with application-specific programmable signal processors. The characteristics of current DSPs are discussed and it explains methods for increasing the throughput of algorithms in DSPs. Chapter 9 deals with multi-processor systems, while implementation strategies are discussed in Chapter 10. Each Chapter ends with a set of exercises which meet the needs of the textbook reader, but they also aid the reference book reader to understand better the topics treated throughout the book.

Mr Pirsch has written a comprehensive guide dealing with all aspects of Digital Signal Processing architectures and their implementation in circuits. Many of the examples used are drawn from the audio and video processing worlds, but the book is primarily geared towards the student or the professional working in the circuit design area. The philosophy of filling a gap between the disciplines of signal processing algorithm development and the design of the final circuits is interesting, and Architectures for Digital Signal Processing provides a useful overview of both areas.

Architectures for Digital Signal Processing
P. Pirsch
Hardbound volume of 419 pages
John Wiley & Sons, Chichester, UK, 1998
Ref: ISBN 0-471-97145-6. Price £39.95

Peter McAvock

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