Digital Video and Audio Broadcasting Technology: A Practical Engineering Guide

PDF Digital Video and Audio Broadcasting Technology: A Practical Engineering Guide 3e Édition, Format Kindle

Book author
  1. Walter Fischer
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Description:

"Digital Video and Audio Broadcasting Technology – A Practical Engineering Guide" deals with all the most important digital television, sound radio and multimedia standards such as MPEG, DVB, DVD, DAB, ATSC, T-DMB, DMB-T, DRM and ISDB-T. The book provides an in-depth look at these subjects in terms of practical experience. In addition it contains chapters on the basics of technologies such as analog television, digital modulation, COFDM or mathematical transformations between time and frequency domains. The attention in the respective field under discussion is focussed on aspects of measuring techniques and of measuring practice, in each case consolidating the knowledge imparted with numerous practical examples. This book is directed primarily at the specialist working in the field, on transmitters and transmission equipment, network planning, studio technology, playout centers and multiplex center technology and in the development departments for entertainment electronics or TV test engineering. Since the intire field of electrical communications technology is traversed in a wide arc, those who are students in this field are not excluded either.

The third edition of this well established reference work includes the new formats MPEG-4 und IPTV, and it already gives an outlook to the newest standards like DVB-SH and DVB-T2.

Introduction:

For many decades, television and data transmission have followed parallel paths which, however, were completely independent of one another. Although television sets were used as first home computer monitors back in the eighties of the century now past, this was the only interaction between the two fields. Today, however, it is becoming more and more difficult to distinguish between the two media of TV and computers which are converging increasingly in this age of multimedia. There are now excellent TV cards for PCs so that the PC can easily become another TV set. On the other side, teletext was introduced back in the eighties to provide an early medium for supplementary digital information in analog TV. For young people, this type of information is such a natural part of viewing, e.g. as electronic program guide, as if there had been teletext from the beginnings of television.

And now we are living in the age of digital TV, since 1995 in fact, and the distinction between data and television has virtually disappeared. When one is able to follow the developments in this field throughout the world like the author has on numerous seminar trips, one will encounter more and more applications where either both television and data services are found jointly in one data signal, or the services are even just pure data services, e.g. fast Internet access via channels which were actually provided for digital TV. The common factor leading to this fusion is the high data rate. Today’s generation is hungry for information and used to getting it in large quantity and variety. Talking to telecommunication specialists about data rates, one hears time and again how envious they are of the data rates used in digital TV. Thus GSM, for example, works with data rates of 9600 bit/sec and UMTS uses a maximum of 2 Mbit/sec under optimum conditions, e.g. for Internet accesses. An ISDN basic access telephone channel has two times 64 kbit/sec. By comparison, the data rate of an uncompressed digital Standard Definition TV signal is already 270 Mbit/sec and High Definition TV begins at about 1.5 Gbit/s and extends into the 3 Gigabit range. One would be fully justified to call television a broadband technology, not only from the point of view of digital TV but even in analog TV where the channels have always been very wide. An analog or digital terrestrial TV channel has a width of 6, 7 or 8 MHz and the channels broadcast via satellite are even 36 MHz wide. It is not surprising that a new boom is being experienced especially in broadband TV cable, which is being used as a medium for high-speed home Internet access in the Mbit/sec range, uplinking via cable modems.

The foundation stone for analog television was laid by Paul Nipkow back in 1883 when he developed what is now known as the Nipkow disc. He had the idea of transmitting a picture by disecting it into lines. The first real analog TV transmissions per se took place in the thirties but, held back by World War II, analog television didn’t have its proper start until the fifties, in black and white at first. The television set acquired color towards the end of the sixties and from then on, this technology has been basically only refined, both in the studio and in the home. There have been no further changes in the principles of the technology. Analog TV transmissions are often so perfect, at least in quality if not in content, that it is difficult to interest many people in buying a receiver for digital TV.

In the eighties, an attempt was made to depart from traditional analog TV by way of D2MAC. For various reasons, this did not succeed and D2MAC vanished from view again. In Europe, the PAL system was given a slight boost by the introduction of PALplus but this, too, did not achieve much success in the TV set market, either. At the same time, various approaches were tried, mainly in Japan and in the US, to achieve success with the transmission of HDTV, but these also failed to gain the universal popular appeal hoped for.

In the studio, digital television signals have been used since the beginning of the nineties as uncompressed digital TV signals conforming to “CCIR 601”. These data signals have a date rate of 270 Mbit/sec and are highly suitable for distribution and processing in the studio, and are very popular today. But they are not at all suitable for broadcasting and transmission to the end user. The channel capacities available via cable, terrestrial channels and satellite would not be even nearly adequate enough for these signals. In the case of HDTV signals, the data rate is about 1.5 Gbit/sec uncompressed. Without compression, these signals could not be broadcast.

The key event in the field of digital television can be considered to be the establishment of the JPEG standard. JPEG stands for Joint Photographic Experts Group, a group of experts specializing in still frame compression. It was here that the discrete cosine transform (DCT) was used for the first time for compressing still frames towards the end of the eighties. Today, JPEG is a commonly used standard in the data field and is being used very successfully in the field of digital photography. Digital cameras are experiencing quite a boom and are becoming better and better so that this medium has replaced traditional photography in many areas.

The DCT also became the basic algorithm for MPEG, the Motion Picture Experts Group, which developed the MPEG-1 standard by 1993 and the MPEG-2 standard by 1995. The aim of MPEG-1 was to achieve the reproduction of full-motion pictures at data rates of up to 1.44 Mbit/sec, using the CD as a data medium. The aim for MPEG-2 was higher and MPEG-2, finally, was to become the baseband signal for digital television world-wide. Initially, only Standard Definition Television (SDTV) was provided for in MPEG-2, but High Definition Television (HDTV) was also implemented which was apparently originally intended for MPEG-3. However, there is no MPEG-3 (nor does it have anything to do with MP3 files, either). In MPEG-2, both the MPEG data structure was described (ISO/IEC 13818-1) and a method for full-motion picture compression (ISO/IEC 13818-2) and for audio compression (ISO/IEC 13818-3) defined. These methods are now used throughout the world. MPEG-2 allows the digital TV signals of originally 270 Mbit/sec to be compressed to about 2 to 7 Mbit/sec. The uncompressed data rate of a stereo audio signal of about 1.5 Mbit/sec, too, can be reduced to about 100 to 400 kbit/sec, typically to 192 kbit/s. As a result of these high compression factors it is now possible even to combine a number of programs to form one data signal which can then be accommodated in what was originally an e.g. 8-MHz-wide analog TV channel.

In the meantime, there is MPEG-4, MPEG-7 and MPEG-21.

At the beginning of the nineties, Digital Video Broadcasting (DVB) was then created as a European project. In the course of this project, several transmission methods were developed: DVB-S, DVB-C and DVB-T. The satellite transmission method DVB-S has been in use since about 1995. Using the QPSK method of modulation and with channel bandwidths of about 33…36 MHz, a gross data rate of 38 Mbit/sec is possible with satellite transmission. With approximately 6 Mbit/sec per program, up to 6, 8 or even 10 programs can now be transmitted in one channel depending on data rate and content and when mainly audio programs are broadcast, more than 20 programs are often found in one channel. In the case of DVB-C, transmitted via coaxial cable, the 64QAM modulation also provides a data rate of 38 Mbit/sec at a bandwidth of only 8 MHz. Current HFC (hybrid fibre coax) networks now allow data rates of more than 50 Mbit/s per channel. DVB-C, too, has been in use since about 1995. The digital terrestrial TV system DVB-T started in 1998 in Great Britain in 2K mode and is now available nationwide. This terrestrial path to broadcasting digital TV signals is being used more and more, spreading from the UK, Scandinavia and Spain all the way to Australia. DVB-T provides for data rates of between 5 to 31 Mbit/sec and the data rate actually used is normally about 22 to 22 Mbit/sec if a DVB-T network has been designed for roof antenna reception, or about 13 to 15 Mbit/sec for portable indoor use. Germany was changing, region by region, from analog terrestrial TV to DVB-T. This change-over was completed in Germany at the end of 2008.

In North America, other methods are in use. Instead of DVB-C, a very similar system which conforms to ITU-J83B is used for cable transmission. Terrestrial transmission makes use of the ATSC method where ATSC stands for Advanced Television System Committee. In Japan, too, other transmission methods are used, such as ITU-J83C for cable transmission, again very similar to DVB-C (which corresponds to ITU-J83A), and the ISDB-T standard for terrestrial transmission. Yet another terrestrial transmission system is being developed in China. The common factor for all these methods is the MPEG-2 baseband signal.

In 1999, another application was given the green light, namely the digital versatile disc, or DVD. The video DVD also uses an MPEG-2 data stream with MPEG video and MPEG or Dolby Digital audio.

In the meantime, the range of digital television has been extended to mobile reception with the development of standards for use with mobile telephones, designated as DVB-H (Digital Video Broadcasting for Handhelds) and T-DMB (Terrestrial Digital Multimedia Broadcasting) and CMMB.

This book deals with all present-day TV compression and transmission methods, i.e. MPEG, DVB, ATSC, ISDB-T and DTMB. The video DVD is also discussed to some extent. The discussion is focused on dealing with these subjects in as practical a way as possible. Although mathematical formulations are used, they are in most cases only utilized to supplement the text. The mathematical ballast will be kept to a minimum for the practical field engineer. This has nothing to do with any possible aversion the author may have against mathematics. Quite on the contrary. In the course of many seminars involving thousands of participants throughout the world, forms of presentation were developed which have contributed to a better and easier understanding of these in some cases highly complex subjects. The book also contains chapters dealing with basic concepts such as digital modulation or transformations into the frequency domain, some of which can be skipped by a reader if he so desires. Experience has shown, however, that it is better to read these chapters, too, before starting with the actual subject of digital television. A major emphasis is placed on the measuring techniques used on these various digital TV signals. Necessary and appropriate measuring techniques are discussed in detail and practical examples and hints are provided.​
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