No. 304 (October 2005)

Bookshelf Archive

Frequency Assignment and Network Planning for Digital Terrestrial Broadcasting Systems

Digital radio and television technology has been developed over the last two decades and is now in the process of replacing the analogue technologies of yore. At present there is much activity within the ITU in preparation for a complete replacement of the analogue broadcasting plans which have governed terrestrial broadcasting in Europe and Africa for over 40 years. The formal basis for this replacement, a full digital Plan, will be established during an ITU Regional Radio Conference in 2006 (RRC-06). It is timely that a book dealing with this topic is now available.

This book provides a clear and complete introduction to the results of years of intense research concerning the planning of the terrestrial broadcasting systems, T-DAB and DVB-T, to be introduced in the aftermath of RRC-06.

In the first chapters, the author describes the underlying modulation techniques that allow digital terrestrial transmissions to cope with multipath propagation conditions and the propagation models which are used to predict coverage and interference.

In contrast to typical assignment planning used for analogue broadcasting, the digital planning for RRC-06 will be based on newer "allotment" planning methods. The author explains the relevant intricacies, ranging from "reference networks" to "single frequency networks" and the related mathematical models that can make planning easier.

A large portion of the book deals with frequency assignment and network planning, giving a large number of practical and theoretical examples. A brief description of graph theory is given, as well as an overview of some related computer-based algorithms and optimisation procedures which can be used for large-scale planning.

Most topics, concepts and underlying principles are presented in complete and fully-explained mathematical detail. However, the book would have been somewhat easier to read, had the Editor taken a bit more time and care...

The book is recommended as a reference source for experts already involved in terrestrial digital broadcast planning, as well as a complete introduction to the subject for students and non-experts who are in the process of becoming involved.

Frequency Assignment and Network Planning for Digital Terrestrial Broadcasting Systems
Roland Beutler
Hardbound volume of 309 pages
ISBN 1-4020-7872-2. Price: € 131.61.
Kluwer Academic Publishers / Springer, 2005
Web Link

Terry O'Leary

(back to top)

A Practical Guide to Video and Audio Compression – From Sprockets and Rasters to Macro Blocks

Good books on digital compression are very few. There are two reasons. Firstly, compression is a relatively new subject and not very many technologist have already acquired hands-on experience of it. Secondly, very few people feel confident to write about this subject, as it is relatively complex and developing rapidly.

Compression is not an exact science. It is a well known fact that there are more than one criteria for determining the quality of a codec and that experts will almost always disagree on which codec is better or worse. This is simply because quality depends on the content, and different assessors have different perceptions of the content. For this reason, designing a codec is considered by many as "black magic".

Nevertheless, compression systems (or their physical implementation – codecs) are fundamental to digital broadcasting and webcasting. There would be no digital broadcasting without a good codec.

But what is a good codec? The answer to this question is simple. A good codec provides the best subjective quality you can get for a given bitrate and cost.

Cliff Wootton's book is great in giving the uninitiated reader an overall review of the key issues relating to audio and video formats, encoding, distributing, storing and rendering. It covers almost any topic from ingest through to rendering in the receiver. The subtitle "From Sprockets and Rasters to Macro Blocks" seems to indicate that the author intends to cover, quite ambitiously, all compression technologies used in broadcasting as well as webcasting. This integrated internet/broadcasting approach is valuable but adds to the volume of the book.

The sheer size of this work is quite impressive: it contains 39 chapters and 14 Appendices, runs to about 800 pages and weights more than two kilograms.

Whilst no doubt this book is an extremely valuable "all-in-one" collation of the various audio and video compression topics, the coverage of many subjects is fairly superficial and provides only little added value for an average practising broadcast engineer.

However, for a non-professional reader the book is very useful. It is relatively easy to read and is well structured. It provides easy-to-follow practical application guidelines and useful step-by-step instructions on best coding and compression practices. The no-math language used is simple and accessible to the non-initiated. Beginners should find the book's introductory chapters – on digital formats and audio/video codecs used in digital broadcasting as well as in multimedia – of considerable value. The book describes file and tape formats, delivery mechanisms, players, pre-encoding procedures and finally encoding itself. Also useful are some Appendices that give practical information as well as the Glossary and the "Webliography" (alphabetical list of some Web addresses).

Because of its size, it makes little sense to suggest that some topics are not sufficiently covered. Nevertheless, it may be useful to talk about the quality aspects of compression and perhaps give more detailed descriptions of coding tools, so that the user would be better armed for carrying out the parametrization of the codecs in practice. As the behaviour of codecs in the presence of channel errors varies dramatically from one codec to another, it would be useful to include a section about the sensitivity of codecs to transport errors and error protection mechanisms, but this would make the book even thicker.

In conclusion, the book provides a useful review of the relevant compression schemes for a non-expert reader. I am not certain that the claim "after reading this book, the reader will be able to prepare and distribute professional audio and video on any platform" is entirely realistic.

It seems that more focused and compact books which cover specific subjects in-depth are often more useful than all-embracing but relatively superficial collations. Today, a keen reader can go to Wikipedia or find other sources of general information on the Internet. A professional reader would probably derive more value from a book which provides new facts and detailed analyses resulting from the author's personal experiences and practical involvement in the subject.

A Practical Guide to Video and Audio Compression
– From Sprockets and Rasters to Macro Blocks
Cliff Wootton
Bound volume of 787 pages
ISBN 0-240-80630-1. Price: £34.99
Focal Press, 2005
Web link

Franc Kozamernik

(back to top)

Video over IP – A practical guide to technology and applications

First of all, a remark about the title of this book. "Video" in the title means not only video but any data including time-sensitive data (video, audio and associated data) and non-time-sensitive data (files and on-demand services).

Secondly, the term "IP" in the title is considered in this book generically and embraces all delivery mechanisms that make use (or can potentially do so) of the Internet Protocol. This includes not only the Internet but also all modern telecommunication networks, wired and wireless, and also some novel broadcast networks (example: DVB-H).

The timing of the publication of this book is well chosen as the relevance of IP increases. Following the transition from analogue to digital, the transport of audio and video over IP is the next paradigm shift. Traditionally, all digital video, audio and data streams and files have travelled over the different terrestrial, satellite and cable networks using the MPEG-2 Transport system. All new networks, both telecommunications and broadcast, use Internet Protocol (IP), together with several associated protocols.

There surely must be solid reasons for IP to become so widely popular in a relatively short time. This book provides numerous arguments in favour of using IP for transporting live TV and VoD files. It is shown that it is actually simpler and cheaper to configure workstations with high-bandwidth networking card (such as Gigabit Ethernet) than it is to equip each workstation with video and audio input/output cards. Compared to other network technologies such as ATM, IP has numerous advantages: variable packet length, no need to set up a connection prior to transmission (IP is "connectionless") and a possibility to prioritise packets when congestion occurs ("DiffServ").

IP has been successfully used for switching video and audio signals in studio LANs (local area networks). The spread of IP technology into the world of broadcast video is continuing into video file storage and retrieval, particularly for supporting digital video editing stations, and live ingest – the process of taking live video content into the digital domain for storage in files on hard disks. Then, live-to-air IPTV is becoming the synonym for new-age interactive television.

Among the downsides of IP are the timing and "best effort" issues. As for the former, the destination devices try hard to collect IP packets arriving at different delays and reconstruct the timing of the original signals. This may often be a tricky process. The "best effort" simply means that the quality of IP video may not often be guaranteed.

This book is an integrator of two distinct technologies: the content formats for both video and transport (IP). Therefore it is useful for both video experts and network specialists to gain some insights into either technology and breach the gap between the two. The book helps both constituencies to make intelligent choices as to which technology is most suitable for a particular purpose or application.

The book is easy to read at different levels – from entry level to expert level. Of particular benefit are the checklist updates at the end of each chapter. This helps the reader to review the key questions addressed in each chapter. These questions are rather intelligent and are taken from real-life circumstances.

IP is now a fashionable subject and there are plenty of interesting books on this subject. I find this book among the better ones, for its systematic approach and clarity of the text. It is an ideal introduction course for the central DVB document on this topic which is DVB Handbook A 086 entitled "Transport of DVB Services over IP". This Handbook was produced by the DVB TM-IPI (IP Infrastructure) working group in July 2004. It specifies how DVB MPEG TS packets containing video, audio and data shall be carried over IP networks in practice.

It should be pointed out however that the DVB Handbook does not consider the transport of video directly over IP. The DVB specification first wraps video and other components into the DVB multiplex and only then puts it on IP. Such a solution was found technically more suitable and commercially more efficient for the first phase of IP implementation, in particular for linear broadcast services. However, the DVB IPI group is now planning to standardize "Video direct over IP" as soon as possible, probably at the beginning of 2006.

The "Video over IP" book is highly recommended for all practising broadcast engineers. As IP is penetrating all areas of broadcast technologies, this book represents an excellent starting point for all of them.

IP can be considered as a link (or a common layer) between all new wired and wireless communications technologies and broadcast technologies. IP may soon become a "must" for any systems and devices that are required to become part of the "networked world".

Video over IP – A practical guide to technology and applications
Wes Simpson
Bound volume of 493 pages
ISBN 0-240-80557-7. Price: £34.99.
Focal Press, 2005
Web link

Franc Kozamernik

(back to top)

European Broadcasting Union L'Ancienne Route 17A CH-1218 Grand-Saconnex Geneva Switzerland techreview@ebu.ch