Digital Television Station and Network …For SD DTV, the choice of digital video format is usually based on the number of lines of the legacy analog system used in that country. Countries

Digital Television Station and NetworkImplementation

GRAHAM A. JONES, JAMES M. DEFILIPPIS, MEMBER, IEEE, HANS HOFFMANN, MEMBER, IEEE,

AND EDMUND A. WILLIAMS, SENIOR MEMBER, IEEE

Invited Paper

The comparatively recent introduction of digital transmissionprovides superior video and audio quality and increased capabili-ties for new services. However, for many years broadcast stationsand networks have been transitioning to digital systems for variousaspects of production and distribution. The introduction of digitalTV has required further major changes to broadcast stations andnetworks, with large capital investments. This paper describessome of the considerations in implementing digital systems forstudios and transmission, and compares broadcast service modelsadopted in various parts of the world.

Keywords—Advanced Television Systems Committee (ATSC),digital audio, digital video, digital television (DTV), Digital VideoBroadcasting (DVB), high definition televison (HDTV), IntegratedServices Digital Broadcasting (ISDB), multiplex, standard defini-tion television (SDTV).

I. INTRODUCTION

In the previous major change in broadcasting, fromblack-and-white to color television, existing black-and-whitereceivers could still display programs broadcast in color, andnew color receivers could display legacy black-and-whitetransmissions. This backward and forward compatibilityconsiderably eased transition arrangements for the industryand consumers. However, this does not apply for the changeto digital television (DTV) transmission, where the digitaland analog broadcasts are incompatible and new equipmentis required both to transmit and receive the new services.

Manuscript received June 6, 2005; revised September 26, 2005.G. A. Jones is with the National Association of Broadcasters, Washington,

DC 20036 USA (e-mail: [email protected]).J. M. Defilippis is with the Fox Technology Group, Los Angeles, CA

90035 USA (e-mail: [email protected]).H. Hoffmann is with the European Broadcasting Union, Geneva, Switzer-

land (e-mail: [email protected]).E. A. Williams, retired, was with the Public Broadcasting Service,

Alexandria, VA 22314 USA (e-mail: [email protected]).

Digital Object Identifier 10.1109/JPROC.2006.861003

Therefore, in the United States and elsewhere, mostbroadcast stations have been required to maintain theirexisting analog transmissions during the transition period,while adding new digital services in accordance with theDTV standard, as illustrated in Fig. 1.

Arrangements for the DTV transition are being im-plemented with different emphasis in various countries,depending on network and station arrangements, govern-ment regulations, and market conditions. In the UnitedStates, recovery of spectrum associated with analog trans-missions is a prime political and technical consideration. InEurope, the use of this “digital dividend” is not yet decided,but current indications are that it will largely be used todevelop further broadcast services.

The move to digital transmission is not the only task forbroadcasters. This paper outlines some of the many imple-mentation issues addressed by terrestrial broadcast stationsand associated networks as they have transitioned to DTV,and indicates some of the approaches adopted. Detailed de-scriptions of the compression and transmission technologies,as well as implementation for digital cable and satellite de-livery, are provided in the respective papers for those topicsin this special issue of the PROCEEDINGS OF THE IEEE.

II. DTV EFFECT ON THE PROGRAM CHAIN

The term DTV is generally applied to a system in whichtelevision programming is delivered digitally to the viewerat home. The various DTV standards provide the capabilityto deliver superior video and audio quality, eliminating thenoise, distortions, and ghosting that can degrade analog tele-vision. DTV also enables new features and services that mayinclude:

• high definition television (HDTV) with higher resolu-tion and wide-screen images;

• 5.1 channel surround sound audio;

0018-9219/$20.00 © 2006 IEEE

22 PROCEEDINGS OF THE IEEE, VOL. 94, NO. 1, JANUARY 2006

Fig. 1. System impact of DTV standard.

• multicasting—delivery of multiple standard definitiontelevision (SDTV) and/or HDTV programs in onebroadcast channel;

• electronic program guide;• data broadcasting content.A DTV channel may carry either HDTV or SDTV pro-

gramming, or possibly both HDTV and SDTV simultane-ously. The number of programs depends on the bandwidth(actually the bit rate) allocated for each program service.

The abbreviations DTV, HDTV, and SDTV are often usedimprecisely or incorrectly. DTV encompasses both SD andHD television but, strictly speaking, the terms HDTV andSDTV relate only to the resolution of the video image and,historically, both HDTV and SDTV have been produced andbroadcast in analog form as well as digital. Today the trendis strongly toward all-digital systems for both SD and HD,although analog SD television transmissions are still ubiqui-tous worldwide and analog HD transmission by satellite isstill operational in Japan (although closing soon).

The enhancements of DTV are enabled by the AdvancedTelevision Systems Committee (ATSC), Digital VideoBroadcasting (DVB), and Integrated Services Digital Broad-casting (ISDB) standards. These are covered in the respectivepapers elsewhere in this special issue of the PROCEEDINGS

OF THE IEEE. The standards relate largely to the format andcontent of the transmitted signals. Nonetheless, DTV has amajor effect on many other parts of the broadcast system. Asan example, Fig. 1 shows a much-simplified program chainfor the legacy analog National Television System Committee(NTSC) [1] and ATSC DTV terrestrial broadcasting froma local U.S. television station, taking programming from anetwork, and transmitting over the air. The ATSC standardapplies directly to the DTV signal emitted by the station, butthe introduction of DTV affects the whole of the programchain including acquisition, production, postproduction,distribution, and transmission, in several ways, as follows.

A. Video Format

Where HD DTV is allowed or required by the regula-tory authority, broadcasters typically need to implement new

equipment for the appropriate HD video format throughoutthe program chain, from image acquisition through to en-coding for transmission. Depending on the DTV standardand regulations for the country, there is a choice of multipleformats based on 1080 or 720 active lines—each with variousadvantages and disadvantages, but outside the scope of thispaper to discuss. The HD formats always use a widescreenpicture aspect ratio of 16 : 9.

For SD DTV, the choice of digital video format is usuallybased on the number of lines of the legacy analog systemused in that country. Countries using the 525-line NTSCstandard normally use a 480 active line DTV format, whilecountries using the 625-line analog standards known asPhase Alternating Line (PAL) [1] or Sequential CouleurAvec Memoire (SECAM) [1] normally use a 576 active lineformat. The SD DTV formats may be implemented in either4 : 3 or 16 : 9 aspect ratios, with a choice (in some countries)of interlaced or progressive scan; this requires changesto production, and monitoring equipment throughout theprogram chain.

The frame rate for both HD and SD DTV programming ina given country is usually based on that for the legacy analogsystem, 25 frames per second (fps) or (approximately) 30 fps(related to the 50- or 60-Hz power frequency for the country).Progressive scan formats may use twice the frame rate ofinterlaced formats. In 60-Hz countries, broadcasters may alsochoose to produce and/or transmit some programming usingthe 24 fps rate with progressive scan, usually associated withfilm. This latter choice requires changes to equipment forproduction and monitoring at various points in the programchain. In 50-Hz countries, film-based material for televisionis usually produced and run at 25 fps.

B. Audio

The main effect of DTV on audio systems is the possi-bility for 5.1 channel surround sound. DTV also allows formultiple languages, audio for the sight-impaired, and otherservices. Legacy analog systems are usually designed fortwo-channel stereo audio (sometimes with provision for asecond, foreign language service). Therefore, production anddistribution for the additional channels for surround sound,

JONES et al.: DIGITAL TELEVISION STATION AND NETWORK IMPLEMENTATION 23

plus possibly more for other services, requires significantchanges to equipment throughout the program chain.

There are also issues related to audio processing and dy-namic range that require audio for DTV to be handled differ-ently from that for analog transmission.

C. Multiple Program Services

Where a broadcaster chooses to transmit multiple pro-grams on one DTV multiplex, expansion of the playoutand master control facilities for the originating station ornetwork (where the program is finally assembled and dis-tributed—see Section X) are required to accommodate theadditional services.

D. Electronic Program Guide and System Information

The inclusion of an electronic program guide (EPG) inthe DTV transmitted bit stream, plus the other service in-formation associated with the program, requires provision ofthe sources needed to produce and update the informationneeded. It also requires methods for communicating it fromthose sources to where the DTV bit stream is generated. Thisinformation enables a DTV receiver to rapidly tune to a se-lected channel and to display program guide information forthe viewer. For more information, please see the paper in thisissue on the ATSC transport layer program and Program andSystem Information Protocol (PSIP). The DVB and ISDBsystems have similar features for electronic program guides,although implementation arrangements are different.

E. Datacasting

Where a broadcaster chooses to include data broadcastingservice in the DTV multiplex, a completely new productionunit may be required to produce such services, and a newinfrastructure may be needed to distribute and integrate theminto the DTV service. More information on data broadcastingservices is provided in related papers in this special issue.

F. Digital Equipment and Infrastructure

As explained in Sections III and IV, in order to main-tain optimum quality and exploit the full capabilities of theDTV system, both transmission and studio systems should bebased on digital signal processing and, in particular, compo-nent digital video (see [2] and [3] for a general introductionto digital video and audio). Most current systems for HDTVhave been designed from the start using digital equipmentthroughout the program air chain. However, much SDTVprogramming still originates from legacy systems originallydesigned to supply signals to NTSC, PAL, or SECAM analogtransmitters. Such systems may still include some analogequipment for production or other parts of the system andarchived program material may only be available in analogform. Therefore, depending on their age, current SDTV pro-gram chains may not be digital throughout.

Irrespective of the transmission format, there are manyadvantages to using digital studio equipment. Not onlycan digital component video and digital audio production,postproduction, archive, and distribution systems greatlyimprove image and sound quality. They can also often

provide enhanced production and creative capabilities andpotentially enable more efficient operations. For these rea-sons, the transition to digital video and audio systems hadbeen underway for many years—long before the change toDTV transmission.

III. SHORTCOMINGS OF ANALOG

A. Composite Video

The traditional analog television standards define not onlythe transmission arrangements but also the composite videoformats used to produce, record, and distribute analog pro-gramming. Composite video has certain fundamental picturequality constraints and artifacts caused by the method of car-rying the color information on a subcarrier within the band-width of the luma (brightness) signal.

B. Noise and Distortion

Analog video and audio signals suffer degradations dueto the introduction of noise and linear or nonlinear distor-tions during processing and distribution. This applies par-ticularly in analog recording systems, where the build-up ofnoise and distortions severely limits the number of genera-tions of recording that may occur while maintaining accept-able quality.

C. Restricted Capabilities

Some desired operational or engineering capabilities orfunctions are impossible or impractical to achieve usinganalog signal processing.

IV. MIGRATION FROM ANALOG TO DIGITAL

A. Digital Studio Islands

The quality and capability restrictions of analog video andaudio drove the industry to develop digital solutions for sev-eral types of studio equipment. Such equipment performedfunctions not possible with analog processing, but they gen-erally stood-alone as digital “islands” in an otherwise analogsystem, with conversion back to analog video and audio sig-nals for all interconnections.

Examples of early digital video equipment islands include:• digital timebase correctors 1973;• frame synchronizers 1974;• digital video effects 1978;• digital videotape recorders (VTRs) 1986.Similar developments for audio during the 1970s and

1980s included:• digital delays, reverberation, and effects units;• digital audio mixers;• digital audio tape recorders;• digital hard disk recording and editing.Digital video and audio equipment such as that listed

above was widely adopted by broadcasters to meet par-ticular functional needs. In a few cases, such islands wereinterconnected with proprietary methods for digital codingbut the absence of practical standardized interfaces hindereddevelopment of fully integrated digital systems.


B. Bandwidth

Current specifications for uncompressed signals requirethe following data rates for baseband serial digital bitstreamson the interfaces:

Stereo (2–channel) audio 3 Mb/s

SD component video(10 bit, 4 : 2 : 2)

270 or 360 MB/s

HD component video(10 bit, 4 : 2 : 2)

1.485 Gb/s.

These bit rates require system bandwidths greatly ex-ceeding those for carriage of equivalent analog signalsand, for many years, the lack of suitable high-speed elec-tronic components impeded development of serial digitalinterconnections.

C. Digital Video and Audio Standards

Interoperable digital equipment and integrated systemsdepend not only on suitable high-speed interfaces but alsoon the relevant open technical standards being established.Some key milestones in this process during the 1980s and1990 were as follows.

1) Digital Video Sampling and Format: A critical stagewas the development in 1982 of an international standardfor the sampling and format of 525- and 625-line digitalvideo systems—CCIR Recommendation 601, now publishedas ITU-R BT.601 [4]. This specification was the basis ofmany subsequent digital video developments and led to thefirst standardized digital VTR (type D1) and other digitalvideo equipment.

2) Serial Digital Audio Interface: In 1985, a digital audiointerface standard was agreed jointly between the AudioEngineering Society (AES) and the European BroadcastingUnion (EBU). The AES/EBU specification [5] allows dis-tribution of uncompressed stereo audiosignals as a serialdigital bitstream. This standard enabled single-cable inter-connections for digital audio and laid the foundation for allsubsequent integrated digital audio systems.

3) HDTV Production Standard: Following several yearsof debate, in 1990 the International TelecommunicationsUnion (ITU) published a recommendation of parametervalues for HDTV standards for production and internationalprogram exchange, now published as ITU-R BT.709 [6].This established a common interchange format for HDTVproduction, which, after further revision, was based on ascanning standard of 1920 pixels by 1080 lines. Later afurther standard of 1280 pixel by 720 lines in progressivescan at a frame rate of 60 Hz was also adopted by the ITU[7].

4) Serial Digital Video Interface: Early digital video in-terconnections were made using bit-parallel interfaces butthis arrangement was found to be impractical for long cableruns, as needed for many video systems. A serial digital inter-face (SDI) for video was conceived and developed during thelate 1980s by the EBU and the Society of Motion Picture andTelevision Engineers (SMPTE), and, in 1993, SMPTE pub-lished its standard for a video serial digital interface (SDI),

SMPTE 259M [8]. This specification relates to video con-forming to ITU-R BT.601 sampling and allows distributionof uncompressed SD digital video signals over a single cable.ITU adopted a similar standard called ITU-R BT.656 [9].These standards enabled the implementation of large-scaleintegrated digital video systems.

5) HD Serial Digital Video Interface (HD-SDI): Theequivalent standard for an HD-SDI, SMPTE 292M [10], waspublished in 1996. The specification defines the interfacefor 1080-line and 720-line video and allows distribution ofuncompressed HD digital video over a single cable. Thisstandard was key to the practical implementation of HDdigital systems.

There are numerous other important standards and rec-ommended practices relating to all aspects of digital videoand audio formats, signals, measurements, and equipmentcharacteristics—far too many to describe here. The majorityhas been developed by SMPTE or the ITU, with others fromthe AES, Consumer Electronics Association (CEA), IEEE,and the Society of Cable Telecommunications Engineers(SCTE), and such standards are listed on those organiza-tions’ Web sites [11]–[16].

V. STANDARD DEFINITION SYSTEMS

Following establishment of the various digital videoand audio standards in the 1980s and 1990s, broadcastequipment manufacturers developed an increasing range ofdigital equipment with serial digital inputs and outputs. Thisallowed the implementation of SD digital video and audioproduction, postproduction, network, and station systems,with superior performance and functionality that eliminatedthe shortcomings of analog mentioned earlier.

During the past 15 years, the trend has therefore been toimplement fully digital studio systems for new SD facili-ties—whether intended to supply signals to analog transmit-ters, DTV transmitters, cable, or satellite. There are, however,still many legacy broadcast stations and facilities in existencebased at least partially on analog equipment, particularly forsignal distribution and routing within the facility.

A. SD Video and Audio Production Equipment

The types of equipment typically included in SD dig-ital video production and postproduction systems includecameras, camcorders, videotape recorders, video servers,editing systems, archives, video switchers, routers and otherdistribution equipment, electronic graphics and charactergenerator systems, digital video effects, frame synchronizers,standards converters, and reference timing equipment.

For audio systems, digital equipment may include mixingconsoles, CD players, digital audio tape and disk recorders,hard disk recorders, audio delay and reverberation, audio ef-fects units, routers, and other distribution equipment.

It is outside the scope of this paper to discuss these typesof equipment individually, but such equipment replicates andexceeds the capabilities and performance of previous analogequipment in virtually every respect.

It should be noted that some organizations continue to useaudio mixing consoles based on analog processing in what


are otherwise largely digital video and audio systems, oreven maintain analog audio distribution in parts of the plant.Analog audio mixers are capable of excellent performanceand, in some cases, the extra cost of replacing analog audioequipment with a fully digital system may not be justified.

B. SD Origination for DTV

Before and during the transition to DTV, networksand stations in most countries have employed studio anddistribution systems built to produce 525-line or 625-lineprogramming for legacy NTSC, PAL, and SECAM trans-mitters. As DTV transmission has been introduced, manybroadcasters have initially used the same studio systemsto produce programming for SD transmissions, with fewchanges in processing apart from conversion to digital sig-nals (if previously in analog at the master control output)and encoding for the DTV standard.

Such programming, if produced and distributed entirelyin the digital domain, using the ITU-R BT.601 standard, willbenefit from many of the advantages of the DTV transmis-sion standard. However, for analog-originated programming,the ultimate quality will usually be limited by the funda-mental restrictions of the analog systems and equipment.

One change that may be needed for DTV is conversionof production and monitoring equipment to handle the 16 : 9picture aspect ratio (see Section VII). While 16 : 9 transmis-sion is not mandatory for SD DTV, some broadcasters maychoose to transmit all or most DTV programming in 16 : 9,particularly as the number of widescreen consumer televisiondisplays increases. Broadcasters in Australia and the UnitedKingdom have already made this SD aspect ratio change,and others in Europe are following soon. However, most U.S.broadcasters still produce and broadcast SD programming in4 : 3 aspect ratio, both for analog and DTV transmission.

VI. HIGH DEFINITION SYSTEMS

HDTV programming requires installation of completelynew production, postproduction, and distribution equipmentand systems—typically a major capital investment for abroadcaster.

A. HD Video Production Equipment

Early HD production systems, developed in Japan in the1970s and 1980s, were largely based on analog technologies,requiring wide-band analog video component interconnec-tions over multiple cables. Equipment tended to be cumber-some and very expensive and overall production capabilities,e.g., video effects, electronic graphics, and editing, were lim-ited compared to SD systems. In 1988 the first HD digitalcomponent VTR, the HDD-1000 was introduced, but sys-tems were still implemented using digital islands with mainlyanalog interconnections.

During the 1990s, manufacturers developed an increasingrange of HD video equipment including new camerasand HD VTRs, including most notably the D5 HD fromPanasonic (1995) and HDCAM from Sony (1997). Theestablishment of the HD-SDI interface in 1996 allowed

practical all-digital HD systems to be implemented for thefirst time. However, prices for such HD production systemswere still much higher than equivalent SD systems, and de-ployment, for the most part, was limited to a small number ofspecialist production companies, major production centers,and networks in countries where HD broadcasting was beingintroduced.

Over the past several years, the range of HD equipmenthas expanded greatly, with new recording and storage for-mats and advances in all types of acquisition, production,postproduction, and distribution systems. At the same time,prices have fallen considerably. This has made it possible forprogram producers, networks and local broadcast stations invarious parts of the world to implement cost-effective HDportable and studio systems with a range of capabilities sim-ilar to or exceeding those for SD facilities.

B. HD Origination for DTV

1) United States: Since the advent of DTV broadcastingin the United States in late 1996, the major networks andmany independent producers have installed new HD produc-tion equipment and systems. The majority of U.S. primetimeprograms and major sporting events are now produced inHD, using systems that are substantially digital throughout.Many scripted drama and comedy shows are produced in the1080-line progressive format at 24 fps, with some acquisitionelectronically and some on film that is transferred to videofor editing and distribution. For live programming and sports,some broadcasters use 1080-line interlaced at 29.97 fps, andothers use 720-line progressive at 59.94 fps.

The major U.S. networks all distribute an HD programservice to their owned and affiliated stations. Most stationsowned by the networks, and very many affiliates, haveequipment to allow such network HD programming to passthrough and be fed to the DTV transmitter. Arrangementsfor this are discussed later in Section X.

Until recently, with some notable exceptions, U.S. localbroadcast stations had not installed significant amounts ofHD studio production equipment. However, an increasingnumber of local broadcast stations are now equipping HDstudios and systems for local news and other productions.Other stations rely on upconverting their local SD programsto the HD format to enable local programming to be in-tercut or mixed with the network programs. Upconversionis a process for increasing the number of pixels and lines inan image by interpolation from existing picture information.

2) Canada: The first HDTV broadcast was in 2003and HDTV is now provided on both cable and satellitechannels. Terrestrial DTV was launched officially by CBCearly in 2005 with some HDTV programming, and otherbroadcasters have announced availability of HD signals.Few shows are, however, currently produced in HDTV.

3) Mexico: The ATSC standard was adopted in 2004. Asyet, HDTV use is limited but terrestrial DTV deploymentis underway and some cable operators already carry HDTVprogramming.

4) Korea: Test transmissions of terrestrial HDTV in SouthKorea started in 1998. Since then, an increasing amount of


HD programming is being produced and broadcast using the1080-line interlaced format at 29.97 fps.

C. HD Origination for DTV—Japan

The Japan Broadcasting Corporation (NHK) and Japanesemanufacturers were pioneers in HDTV production in the1980s, with analog systems using the 1125-line Hi-Vi-sion system and later with digital systems and equipment.In 1997, the HDTV format using 1080 line interlaced at29.97 fps was adopted for digital broadcasting in Japan.

NHK has long experience in HD production, both in thestudio and at remote sites, including the Olympic Games,going back to 1984. A wide variety of programming has beenproduced.

At this time (September 2005), all networks (NHK andfive commercial broadcasters) have completed their HD in-frastructure in the station. Basically, the station is imple-mented throughout with HDTV including facilities for studioproduction (including the news studio), editing, and mon-itoring. Archive SD material and incoming programs fromoutside that is in SD are upconverted to the HD format in thestation.

Facilities for remote news production (ENG camera, etc)in HD will be completed in 2006.

An implementation program for remote production willbe complete before 2008, including interconnection facilities(FPU, Telco line, satellite links, specified fiber, etc.)

It is expected that Japanese local broadcasters will followthe networks and will complete their transition to HD before2008. Currently 80% of all local broadcast programs are pro-vided by the networks.

D. HD Origination for DTV—Europe

Interest in HDTV began in Europe in the early 1990s.When efforts to persuade North America to move toa worldwide common HDTV 80-Hz standard failed, a1250/50 format was proposed for the 50-Hz world. Ananalog HDTV transmission format, HD-MAC, was devel-oped for satellite and cable broadcasting of 1250/50 in thelate 1990s. However, market research showed that HDTVreceivers at that time would be too bulky and expensivefor the European public, and it also seemed better to delayHDTV for a future with digital broadcasting and, hopefully,cheaper and more consumer-acceptable HDTV receivers.HD-MAC was not used, and instead energies were focusedon developing digital broadcasting, initially for SDTV, withmulti channel delivery via digital satellite, digital cable, anddigital terrestrial, through the DVB project.

The age of consumer-acceptable HDTV receivers, withflat panel displays, has clearly arrived, and consequentlyHDTV is now being planned and implemented. Europenow exhibits a limited availability of HDTV services byEuro1080 (HD-1), and some test broadcasts (Pro-7 Ger-many). There are announcements for HDTV from TF1 andCanal+ in France, and confirmation for HDTV services in2005/2006 by Pay-TV operators such as Premiere in Ger-many and BSkyB in the United Kingdom. These services

will be based on generation one and generation two HDTVsystems [18]. Generation one is defined as 1080i/25 and720p/50 with MPEG-2 compression in emission; generationtwo as 1080i/25 or, preferably, 720p/50 with advancedcompression such as MPEG-4 Part 10/H.264 in emission.In accord with the increasing interest, a number of nationalHD-Forums have been established in Italy, the UnitedKingdom, Germany, France, Spain, Portugal, and the Nordiccountries. The EBU established a European HDTV Forumumbrella group for these forums, with a focus on coordina-tion with respect to interoperability questions.

The EBU has recently specified in EBU Tech. 3299 [19]four baseband systems considered relevant for HDTV pro-duction in Europe. These are:

• System 1 (S1) with 1280 horizontal samples and 720 ac-tive lines in progressive scan with a frame rate of 50 Hz,16 : 9 aspect ratio;

• System 2 (S2) with 1920 horizontal samples and 1080active lines in interlaced scan with a frame rate of 25 Hz,16 : 9 aspect ratio;

• System 3 (S3) with 1920 horizontal samples and 1080active lines in progressive scan and a frame rate of25 Hz, 16 : 9 aspect ratio;

• an evolutionary System 4 (S4) with 1920 horizontalsamples and 1080 active lines in progressive scan at aframe rate of 50 Hz, 16 : 9 aspect ratio.

Based on intensive research [20]–[23], the EBU agreedand published a recommendation for HDTV [24]. Thisstates that a progressive HDTV video format is the preferredHDTV system for emission. Currently this should be ac-complished by the 720p/50 system but it is envisaged thatin the future a 1080p/50 system might be an appropriateoption. In accord with this conclusion, new research andwork is under way to investigate a progressive 1080p/50HDTV production and emission chain.

On the consumer equipment side, the European Informa-tion and Communications Technology Industry Association(EICTA) [25] has agreed on an industry specification forHDTV-capable displays, called “HD-Ready,” and a specifi-cation for the minimum requirements for HDTV receivers,including the interface to such displays. They include logosto be used for devices meeting the requirements.

In summary, it is assumed that HDTV in Europe will be anatural evolution of television. Pay-TV operators will firstintroduce HDTV services to the market and large publicbroadcasters will follow during the years to the end of thedecade. Important factors include the penetration and avail-ability of HDTV displays, receiver devices and sufficientHDTV broadcasts so that the consumer feels attracted to thenew experience.

E. HD Origination for DTV—Australia

The Australian DTV system requires SDTV transmissionwith some percentage of simulcast HDTV. However, theplanned quotas for HD have not fully materialized andmuch of the HD output is in fact currently upconverted SDmaterial produced to the ITU-R BT.601 standard.


VII. ASPECT RATIO AND IMAGE DISPLAY ISSUES

During the DTV transition period, some programmingmay be produced with 4 : 3 aspect ratio and some with 16 : 9aspect ratio, depending on its original format and source. Inmost countries, there is also an installed based of televisionreceivers and monitors of both aspect ratios. Therefore, itis necessary for broadcasters and receiver manufacturersto ensure that images shot in one aspect ratio will be dis-played satisfactorily when transmitted and/or displayed ina frame of a different aspect ratio for DTV and/or analogservices. Techniques for aspect ratio conversion include“letterboxing” and “pillar boxing” where bars are added tothe top and bottom or sides of the picture. They also includecropping the picture to change its shape, or the processof pan-and-scan where the desired portion of the frame isidentified and extracted dynamically. New productions canenforce “shoot-and-protect” where critical picture elementsare restricted to portions of the frame that will always bedisplayed. Implementing these arrangements in a productionand distribution environment can be a challenge,

The ATSC and DVB standards define parameters that maybe included in the transmitted bitstream to indicate the activepicture area, for the case when this does not fill the wholeencoded frame. This active format description (AFD) and bardata (ATSC only) can be used by a receiving device to helpoptimize the displayed picture.

VIII. SURROUND SOUND

5.1 channel surround sound transmission for both SD andHD programming is enabled by DTV. However, it is notmandatory in any of the transmission standards and stereoor mono audio meets regulatory requirements. The imple-mentation of surround sound production has therefore variedsomewhat with different program producers and broadcastersin different parts of the world.

Surround sound programming requires production, net-work, and station facilities to have audio systems that canhandle six discrete channels of audio (eight if a stereo mixis also distributed). In particular, audio mixers, monitoring,switching, and distribution systems, previously intended forstereo audio only, all have to be upgraded with provision forat least six or eight-channel operations.

It should be noted that, for many years, surround soundwith four channels has been distributed using a matrix systemfor encoding the center and surround channels onto a two-channel stereo signal. 5.1 audio for DTV, with six discreteaudio channels, provides a much-improved surround audioexperience for television viewers.

Major networks and some independent producers in NorthAmerica have made the investment in new equipment for 5.1surround sound and a substantial amount of U.S. primetimeHD programming is now produced and distributed with sur-round sound. Many, but not all, U.S. local network stationshave installed equipment that allow this programming to bepassed through and fed to the DTV transmitter with surroundsound encoding for the DTV standard. Other stations stillbroadcast in stereo only.

Similarly in Europe, Japan, and elsewhere, there is an in-creasing amount of HD or SD programming produced with5.1 channel surround sound audio. However, broadcast DTVservices still generally include some programs with matrixsurround sound and some with stereo audio.

A. Multichannel Audio Recording and Distribution

The need to distribute and record surround sound signalswith six channels of audio initially created a problem be-cause some VTRs have only two or four audio channels, andlegacy network distribution systems typically carry one stereoaudio signal (often with a second for an alternative language).One early solution for recording was to use a separate multi-track audio recorder synchronized to the video recorder usingtimecode [26]; this is known as double-system sound. This ar-rangement enables all needed sound channels to be recorded,with the disadvantage of a considerable increase in systemcomplexity. Some recent HDTV VTRs now have multipleaudio channels on board for surround sound recording.

One early distribution solution was simply to increase thenumber of discrete audio channels in the studio and net-work distribution, with consequent increase in complexityand cost.

Another solution sometimes used for network distributionis to use emission compression encoding equipment, suchas Dolby AC-3. However, emission compression modes arerather fragile and begin to degrade audio quality after twoor three encode/re-encode cycles. Some U.S. networks (e.g.,ABC) use AC-3 running at a higher bit rate (e.g., 640 kb/s)than is used for emission. The increased data rate reducesthe quality degradation that otherwise can occur when suchsignals are decoded back to base band at the local station andreencoded for emission

B. Embedded Audio

It is possible to embed digital audio signals in the ancil-lary data space available in both SD and HD serial videobitstreams using the SMPTE 272M standard [27]. Up to 16audio channels (eight 2-channel pairs) can be carried in thisway. The technique has many advantages for distributionwithin a plant, but creates additional complexity wheneverthe video and audio signals need to be processed, mixed, orswitched separately, and is not applicable when the video hasto be compressed for distribution over network links.

C. Dolby E

An alternative solution for both recording and distribu-tion uses a coding system called Dolby E [28], developedby Dolby Laboratories. This can be used to lightly compressup to eight audio channels into the bandwidth occupied by asingle two-channel AES/EBU digital audio signal (3 Mb/s).The signal can be recorded onto a VTR or video server andcan be distributed over an AES/EBU audio channel from aproduction facility to the network, and on to the broadcaststation. There it can be converted back to individual audiochannels for mixing and switching in master control, and fi-nally reencoded as AC-3 audio for transmission. The DolbyE signal can withstand up to 20-plus encode/decode cycles.


Although an efficient method for recording and distribution,it does, however, introduce some extra system complexity formonitoring and postproduction.

IX. IT-BASED EQUIPMENT AND SYSTEMS

The architecture for the first digital broadcast studio sys-tems was very similar to traditional analog systems. Audioand video equipment was largely based on custom hardware;with point-to-point dedicated interconnect cabling using se-rial digital bitstreams and crosspoint matrix routing.

Recent developments have enabled most video and audiorecording and processing tasks to be carried out using com-puter-based equipment. Related to this is the ability to storevideo and audio material as computer files, and to transferthem over standard computer networks. The introduction ofsuch systems has taken place in parallel with, but separatefrom, the change to digital transmission.

Some of the most significant new equipment types are harddisk based video and audio servers and nonlinear editingand postproduction equipment. These, and associated sys-tems based on information technology (IT), cover very manyparts of the broadcast chain from acquisition to on-air playoutand have triggered a revolution in system architecture, work-flow and operational practices.

This major change in broadcast technologies was analyzedand, to quite a large extent, enabled by a joint EBU/SMPTETask Force for Harmonized Standards for the Exchange ofProgram Material as Bitstreams. The report [29] of that groupwas the foundation for many of the advanced digital televi-sion standards and techniques in use today.

A. File Transfer

In traditional analog and digital systems, audio and videoprogram material exists as linear signals that are producedand distributed in real time. Such signals are usually recordedto, and played back from, videotape machines in real time.Now that digital audio and video material is increasinglystored on hard drives in the form of computer files, suchmaterial can also be accessed at random and can be trans-ferred as files over the network to another local or remotelocation. This may allow faster than real time distributionover high-speed networks (depending on the video formatand the network capability) or, when necessary, transfer atlower speeds over restricted bandwidth links.

These techniques are now widely used within and betweenproduction and postproduction facilities. They will be in-creasingly used for program distribution to network releasecenters or to on-air transmission points in advance of trans-mission time.

B. MXF, AAF, GXF, and Metadata

The transition to digital video and audio systems has re-sulted in numerous different video and audio compressionand storage formats, some derived from videotape systems,and now used for server-based file storage and distribution.A recent suite of SMPTE standards known as Material eX-change Format (MXF) [30] enables disparate systems fromdifferent vendors to have a common standard file wrapper

that allows seamless interchange of material. This appliesparticularly for distribution of finished programs but also forsequences of clips or program segments. A related set of stan-dards, published by the Advanced Authoring Forum (AAF)is intended for interchange of material in the postproduc-tion process where complex edits and effects are required.The General Exchange Format (GFX) is a third interchangeformat designed primarily for on-air applications.

Television programming has always had metadata (de-scription of the program essence) associated with it, if onlya written label describing the title, video format, and length.The MXF, AAF, and GXF standards make extensive use ofmetadata for the production and technical characteristicsof the material, as a fundamental part of the electronic filesystem and interface and this makes these technologies verypowerful tools for media production and management. Theseinterchange formats all have a foundation in the metadatastandards published by SMPTE [31].

X. MASTER CONTROL AND EMISSION ENCODING

A. Master Control for DTV

Master control areas contain the equipment for control andmonitoring of the on-air program, whether from a networkrelease center, a station group centralcasting location, or alocal station. In a DTV facility, the master control outputis usually fed to compression equipment for distribution oremission. The system architecture for these functions variesconsiderably for different networks and stations. It also de-pends on the number of program outputs and whether ser-vices are in SD or HD, so what follows should be consideredas an example only.

Fig. 2 illustrates in very simple terms how a master con-trol and emission encoding system may be configured fora local U.S. DTV broadcast station. It shows various local,remote, and network sources feeding (a term often usedin broadcasting meaning “sending signals to”) a basebandmaster control switcher, which may be either SD or HD.The switcher is used to select the program source to betransmitted. The video and audio outputs from this switcherthen feed the ATSC video and audio encoders and multi-plexer (mux), and the mux output goes to the transmitter.Audio processing before coding for emission is not neces-sarily required, but is implemented by some broadcasters.Arrangements for a network master control may be similar,but the master control switcher output in that case will feedthe encoders for the network or group distribution, and thengo to a satellite uplink rather than a terrestrial transmitter.

Where a station operates two or more separate programservices, e.g., for multiple SD programs or one SD andone HD, there may be a separate master control area foreach service. Alternatively, one master control position maybe configured to control two or more switchers from thesame control panel, and this arrangement will usually applywhen a station operates several DTV program services formulticasting. Control of the master control switcher by anautomation system is a critical part of station operations,especially for multiprogram services.


Fig. 2. Master control and encoding.

B. MPEG Encoding and Multiplex Systems

As shown in Fig. 2, the video compression is carried out ina video encoder, and the audio compression is carried out inan audio encoder, as described in the related papers on thosetopics. The vast majority of terrestrial DTV services world-wide currently use MPEG-2 video encoding, but in some cir-cumstances advanced codecs such as MPEG-4 Part 10/H.264and Windows Media 9 (or the SMPTE standardized version,VC-1) are beginning to be introduced. H.264 will probablybe used exclusively for HDTV broadcasting in Europe.

Each encoder produces an elementary data stream, whichis combined into a single program stream in a multiplexer.The output of this multiplexer is then combined, in a secondmultiplexer, with other data packets to produce the finaltransport stream that is fed to the transmitter.

Depending on the equipment design, the multiplexers maybe separate devices or may be in a single box integrated withthe video encoder. The audio encoder may be combined inthe integrated unit (common for two-channel encoders) ormay be a stand-alone device (usual for 5.1 channel encoders).

It is most common for a station to locate the encodingand multiplexing equipment at the studio center and sendthe single transport stream over the studio-transmitter-link(STL) to the transmitter (see Section XII), but other arrange-ments are possible.

C. Bit Rates

Bit rates typically used for SD video for emission en-coding with MPEG-2 compression may range from about2 to 8 Mb/s, depending on the program content and desiredquality level. Bit rates for HD video may range from about12 to 18 Mb/s depending on the video format, programcontent, and desired quality level. These bit rates can begreatly reduced by using one of the new advanced codecs.Bit rates used for the audio content are typically in therange 192–448 kb/s per service, depending on whether theprogram is stereo or 5.1 surround. A small amount of databandwidth is required for system information and metadata.In addition, some bandwidth may be allocated for databroadcasting services. In all cases, the total bit rate allocatedcannot exceed the capacity of the broadcast transmissionchannel—between about 14 and 23 Mb/s, depending on the

RF channel, forward error correction (FEC), and modulationscheme in use, as defined in the various terrestrial DTVstandards.

D. Multicasting Operations

Fig. 2 illustrates one possible basic station output arrange-ment for a single DTV program service. However, when sta-tions multicast two or more program services in a singleoutput bitstream on their DTV channel, there will be multiplevideo and audio feeds (the broadcasting term for the signalbeing sent) from master control, to multiple video and audioencoders. These other program services are all combined inthe final mux, as indicated in the figure.

In general, increasing the number of programs in one mul-tiplex results in lower picture quality and more visible arti-facts, but this depends very much on the format of the videocarried and the program content. When multiple programare carried, statistical multiplexing may be used, which canimprove the quality of each service considerably. Statisticalmultiplexing allocates available bandwidth to each programon an as-required basis, rather than using a fixed bit rate foreach one. The random (statistical) nature of video means thatpeak bandwidth requirements for multiple programs rarelycoincide.

E. Remultiplexing

Some networks distribute a multiplex of programs andlocal stations or regional centers may need to modify themix with local programming. In this case, the incoming bit-stream is fed to the multiplexer where it can be reconfiguredby adding or dropping program elements.

F. Closed Captioning Equipment

It is outside the scope of this paper to cover how closedcaptions (subtitles intended to allow deaf people to followthe program audio) are generated and carried, but most pro-grams will be received from the network or other supplierwith caption information carried along with the video signalbut not visible. Live local programs, such as news, are typi-cally captioned at the station, although the person producingthe captions can, in fact, be located off-site and provide theservice remotely.


The caption information may be carried in the studiocenter embedded as data in the digital version of the videovertical blanking interval or vertical ancillary data space(VANC) [32]. Those elements are not encoded for transmis-sion. Therefore, the caption information has to be extractedand placed in the appropriate place in the DTV encodedvideo bitstream for transmission. This process may takeplace entirely inside the encoder, or may require an externaldevice, called a caption server, as shown in Fig. 2. Thecaption server is also needed if DTV captions are beinggenerated locally.

G. PSIP or EPG Generator

For an ATSC station, the PSIP tables are produced in thePSIP generator computer. The output of this is a data streamfeeding the ATSC multiplexer, as shown in Fig. 2. ThePSIP generator may be connected through a network withother computers, such as the traffic system, and automationsystem, which produce and manage the program scheduleand associated information needed to generate the PSIPtables.

H. Data Broadcasting Equipment

If present, a datacasting service may be combined with thetelevision programs in the multiplexer at the output of the stu-dios. This requires a data connection to the multiplexer fromthe data server as shown in Fig. 2. The data server stores andcommunicates the content of the data service. It is usuallyconnected through a network with other computers, either atthe station or elsewhere, which produce and manage the datainformation.

I. Alternative Master Control Arrangements

The previous sections on master control and encoding as-sume that the DTV program feed from the network is re-ceived and converted to baseband video and audio beforebeing distributed at the station, switched to air through amaster control switcher, and then encoded for transmission.

Not all networks and stations follow this model, however.Another possible arrangement, used by two U.S. networks(Fox and PBS) is to carry out ATSC encoding at the networkrelease center and distribute this emission-level (19.39 Mb/s)compressed signal to the affiliate stations. Local program-ming is encoded for transmission at the affiliate station andground terminal equipment is provided there that is capableof MPEG splicing to enable the transitions from localprogramming and interstitials to network programming asrequired. Such compressed bitstream splicing allows for theseamless integration of MPEG program streams, such thatthe decoder in the viewer’s home (as well as the viewer) isunaware that the network and local material was not encodedby one single encoder. To be useful in today’s television en-vironment, other functionality needs to be implemented thatallows local station identification and branding, includinggraphic overlays (both static and dynamic), video sizing,as well as audio voiceover. These must be implementedwithout the complexity and quality degradation of decodingthe whole signal back to baseband and reencoding for trans-

mission. Some of these features have been implemented,while others have been demonstrated and will be deployedin the near future.

Other arrangements are possible, and the decoding,switching, distribution, and emission encoding arrange-ments at different stations vary considerably.

XI. NETWORK DISTRIBUTION ARCHITECTURE

This section is written largely from a U.S. perspective,where several different strategies have been used for distri-bution of DTV programming from networks to local broad-cast stations, largely driven by the need for HD programdistribution. The basic concepts and choices are similar fordifferent countries, but there are many possible configura-tions and variations, particularly where distribution of severalbitstreams with many programs is required, e.g., as for theU.K. Freeview service. Factors to be considered include thenumber and location of the network release facilities, localstations, and transmission facilities; the multiplex configura-tion; and sources of programming.

It should be noted that architectures and implementationarrangements for network distribution are still being devel-oped and improved.

A. Background

HD service from national networks has evolved from thelaunch of DTV service in the United States until today. Eachnetwork has had unique challenges and applied unique so-lutions. In general, the solutions have been digital and havecovered the country using geosynchronous communicationssatellites. In the early years, when HDTV programmingwas sparse, most networks used ad hoc distribution thatused spare transmission capacities with limited capabili-ties. HD playout facilities were islands within the normalSD infrastructure (which in some cases was still analog).As time progressed and the amount of HD programmingincreased, these ad hoc distribution systems were replacedby homogeneous digital satellite systems that transport bothHD and SD programs.

B. Link Platforms

Aside from local links from the network satellite receivepoint to an affiliate station, which may use fiber or microwavetransmissions, all national network HD programming in theUnited States is delivered by satellite, with its easy imple-mentation of point to multipoint distribution. Digital satellitesystems are in use that deliver data rates from 30 Mb/s (usingQPSK) to greater than 70 Mb/s (using 8 PSK) depending onthe ground terminal G/T as well as group delay and LNBphase noise performance.

Satellite systems are also used for many contribution cir-cuits but fiber-optic cables are a viable alternative, since suchlinks are often point to point or with a limited number of des-tination drops.

C. Compression Levels

There are many different compression and coding methodsin use by the networks to deliver digital HD programs. For


live contribution feeds to network centers, MPEG-2 en-coding is typically used with 4 : 2 : 2 sampling and data ratestypically in the range 35–45 Mb/s. For distribution fromnetwork centers to local affiliate stations, most networksuse MPEG-2, long GOP, 4 : 2 : 0 profile, with data ratestypically in the range 25–40 Mb/s, although one network(CBS) is moving to 4 : 2 : 2 sampling at 43 Mb/s for networkdistribution.

At the affiliate station’s satellite receive site, the receiveequipment decodes the compressed satellite HD program andsupplies an uncompressed HD video signal. This signal iseither routed to the stations HD master control (see Fig. 2)directly, or, if the receive site is not collocated, compressedagain and sent via terrestrial microwave or via fiber (uncom-pressed) to the station master control.

Compressed data rates that fall between the fully com-pressed rate required for emission (about 20 Mb/s) and un-compressed HD video (about 1.5 Gb/s) are referred to asmezzanine levels. Using these for contribution and distri-bution links allows compression to be less aggressive. Thisenables multiple cycles of encode/decode and video pro-cessing between encode passes without degrading the finalcompressed program for emission. Rates around 45 Mb/s, asmentioned above, may be considered low-level mezzanine.The use of higher rates (100–400 Mb/s) would provide higherquality margins, but there are no available national satellitedistribution systems that can deliver such high bit rates.

D. Distribution Compressed for Emission

Two national U.S. networks, Fox and PBS, have im-plemented their national HD program distribution with amodel using emission level encoding at the network releasecenter. In order to avoid unacceptable video (and audio)quality degradation by decoding such signals to baseband atthe station and reencoding for emission, the use of MPEGsplicing is required, as discussed earlier in Section X-I. Thisapproach saves distribution bandwidth (both over satelliteand locally) as well as improving video quality by avoidinga decoding/encoding step. The network emission codingcan be either constant bit rate (CBR) or variable bit rate(VBR) with the advantage of minimizing bandwidth usedboth over the satellite as well as providing more bandwidthfor secondary programs (such as weather or news channels)that the local affiliate station may broadcast on its multiplex.

E. Audio Distribution

Some distribution systems use MPEG-2 Layer 2 audiocoding for two-channel audio distribution. As mentioned inSection VIII, distribution for surround sound audio may usehigh-rate AC-3 encoders or the more robust Dolby E. Thosenetworks that use emission level coding and MPEG splicingcan utilize the bit efficiency of emission-rate AC-3 withoutthe degradation of reencoding, thus saving more bandwidth.

XII. TRANSMISSION SYSTEMS

This section is written largely from a U.S. perspective,with reference to the ATSC 8-VSB transmission stan-dard. However, most of the basic concepts and choices are

similar for different countries, although various parame-ters—particularly frequency bands and power levels fortransmitters—will vary significantly. Factors to be con-sidered include frequency allocations and availability ofspectrum, number and location of stations and transmissionfacilities, and population areas to be covered

A. Background

The output of the television studio, whether analog or dig-ital, feeds the STL, which in turn feeds the broadcast trans-mitter. Over the air signals are used in several ways:

• direct reception by tens of millions of viewers providedby tall television towers;

• reception at tens of thousands of cable headends for re-distribution to subscribers;

• extended reception by thousands of television transla-tors serving small communities that are isolated fromthe coverage of the large broadcast transmitters.

This combination provides television signal coverage toover 99% of the U.S. population. A complex and expensivebroadcast infrastructure has grown over the past five decadesthat in the United States utilizes much of the VHF and UHF(plus some SHF) spectrum and requires extensive reserve ca-pacity and backup transmission and power supply facilities.The change to digital transmission in effect requires a du-plication of these facilities during the transition and a hard-ening of those new facilities to continue to maintain a reliablebroadcast service.

The DTV signal is a complex work of engineering thatincorporates:

• MPEG-2 compressed digital video and audio;• a transport stream containing multiple video, audio, data

services, system information, and PSIP signaling;• 8-VSB modulation techniques, combined with pow-

erful error reduction coding that provides a signal thatneeds only about 15-dB signal-to-noise ratio for perfectreception (even less if the new standard for EnhancedVSB transmission is used), which is also shaped tosharply attenuate the signal to fit within a 6-MHzchannel.

The new digital facility needed to place this signal on airrequires a new STL, digital transmitter, bandpass filter tomeet Federal Communications Commission (FCC) maskrequirements, transmission line, antenna, and test andmonitoring equipment. The addition of the componentsto typically already crowded transmitter buildings oftenrequires new building construction, and the DTV antennamay require a new tower or strengthening of an existingstructure.

B. Coverage, Frequency, and Power

Based on assessments of various planning factors and thecharacteristics of the 8-VSB DTV signal, the FCC assigneda new DTV channel and power for each analog licensee that,for most stations, was designed to replicate their currentanalog coverage area.

Many VHF analog stations were assigned new channelsin the UHF band. The shift from VHF to UHF for digital


resulted in much higher power levels to achieve the same cov-erage. For example, VHF stations operating at 100 kW (max-imum for channels 2–6) or 316 kW (maximum for channels7–13) peak effective radiated power (ERP), the move to UHFgenerally required nearly 1 MW average ERP to achieve sim-ilar coverage for the DTV signal. While higher gain antennasfor UHF help reduce transmitter power, the difference was sogreat that most stations with a new UHF DTV assignment de-cided to begin operation with lower than authorized power toreduce both purchase and operating costs.

On the other hand, UHF analog stations with a new UHFdigital assignment found that they needed lower radiatedpower to achieve comparable coverage. For example, a max-imum power analog UHF station at 5 MW ERP required lessthan 500 kW ERP for comparable DTV coverage on UHF.This fact is due to the unique characteristics of the digitaland analog signals, propagation differences between UHFand VHF, and revised planning factors for DTV reception.Note that analog power is measured to accommodate thepeak synchronizing signal while digital signals are measuredas average power because of their consistent and wide-bandspectral characteristic. Transmitted 8-VSB signals have apeak-to-average ratio of about 7 dB. Field tests backed upby laboratory analysis demonstrated that digital signals canbe received perfectly (albeit not always reliably) at 12 dBbelow the point at which an analog signal becomes less thanpassable quality (Grade B).

C. DTV Transmitters

The change to digital forms of modulation from thetraditional analog technology required a reassessment oftransmission system parameters including power levels,linearity, frequency response, out-of-band emissions, andreliability. Meeting the higher standards required of dig-ital facilities meant new research and development effortson the part of equipment manufacturers who successfullydeveloped linear amplifiers and high-level bandpass filtersmeeting the stringent out-of-channel emission limits. These,in turn, allow adjacent channel operation either with analogor digital television broadcast signals.

D. Antenna Systems and Towers

A new DTV antenna, often on a different band, is neededin addition to the existing antenna. Most stations have foundthat their existing tower will not support the new antennawithout modification and strengthening, often at a cost insome cases nearly equaling that of a new tower. In othercases, there was no alternative but to plan for a new and ex-pensive tower. However, a new tower frequently takes yearsfor approval and construction. Some stations are still waitingfor local approval for a new tower.

E. Shared Facilities

In some markets, broadcasters have formed collaborativeorganizations to establish a common transmitter and antennafacility. In dozens of these cases, towers, buildings, and an-tennas are shared by two or more stations resulting in costsavings for equipment purchase and maintenance. Another

important benefit is that it provides a single common direc-tion for viewers to aim their receive antennas. The classicexample is DTV Utah in Salt Lake City, where eight stationscollaborated to build a single building and two towers in-stead of multiple individual towers and buildings at differentlocations.

F. Studio–Transmitter Links for DTV

Most stations have their transmitter located well awayfrom the studio, which may be in a downtown area con-venient for businesses and personnel connected with thebroadcast operations. To interconnect the two locations, anSTL is employed which may consist of a one or two hopmicrowave relay in the 2-, 7-, and 13-GHz UHF and SHFbands or a fiber-optic cable provided by a local commoncarrier. The microwave system is owned by the station andrequires only a line-of-sight path and coordination withother users of the bands to insure interference free operation.The fiber-optic circuit is leased from a common carrier butbecause the path is on or in the ground, it is susceptible tooccasional outages due to rerouting and inadvertent damagefrom construction crews digging up conduits and truckstoppling telephone poles.

Converting a microwave STL for DTV operation meansreplacement of the transmitters and receivers (usually mainand backup). In some cases, dual-use microwave systems areemployed to carry the program signals for both the analogand digital transmitters. Depending upon the lease terms, afiber-optic STL can be converted or modified to carry bothanalog and digital broadcast signals to the transmitter site.

G. DTV Translators

Just as broadcasters need a new transmitter to accommo-date digital transmissions from their main station, the com-paratively low power translators serving isolated and smallercommunities also need a new facility to provide the signalfor the new digital service.

Translators receive their input signal over the air from fullpower transmitters that are often over 100 mi distant. With somany new DTV stations using previously unused channels,interference to translator input as well as output can occur,making the implementation of DTV translators more diffi-cult than for analog facilities. Because translators operate atcomparatively low power levels, the FCC may, under certainconditions, permit a relaxed out-of-channel emission maskfilter to be employed, which will substantially reduce instal-lation cost and complexity.

Translators traditionally convert an incoming analogchannel to a different output channel through a heterodyneprocess, rather than demodulating the signal to video andaudio baseband and remodulating to obtain the outputchannel. While this heterodyne process eliminates degrada-tion due to demodulation and remodulation of the signal,the signal can still be degraded by noise and interferencein the transmission path. When using a string of translators(daisy chain) the reduction in quality can be serious. DTVtranslators overcome this deficiency by demodulating thesignal to the transport data stream, which can be recovered


with virtually no errors and remodulating the transport datastream for transmission on the new frequency. As a result,the quality remains the same as the original transmission.Multiple hops of translators using this technique have noadverse effect on the end users video and audio (either cableTV headends or direct to the home), including HD video and5.1 surround sound. This fact alone provides an incentive toimplement DTV translators earlier in the transition process.

The cost of a DTV translator can be lower in some re-spects but higher in others than an equivalent analog trans-lator. Lower DTV output power provides the same coverageas analog but the DTV remodulation process is more expen-sive than simple heterodyne conversion or analog remodu-lation. It is expected that DTV remodulation costs will dropsubstantially in time and with volume purchases. Today thereare 4400 analog translators serving about 7% of the total tele-vision audience.

H. Costs

DTV transmitter prices range from $50 000 for alow-power DTV to nearly $1 000 000 for high-powerUHF facilities and about $500 000 for VHF DTV facilities.In addition to the cost of the transmitters, a range of ancillaryequipment costing from $50 000 to $250 000 is necessaryto provide long-range support and reliability. This would bein addition to the cost of the antenna, tower changes, andinstallation.

Recognizing that there are more than 1700 full power sta-tions and over 2500 low-power stations (including stationslicensed by the FCC as Class A, which allows higher powerlevels in some circumstances) in the United States, it is clearthat the cost to broadcasters in carrying out the transition todigital transmission is tremendous. It represents a substantialinvestment that many broadcasters believe will not result inpayback for many years to come.

XIII. TEST EQUIPMENT

Since digital television signals are so fundamentally dif-ferent from analog, DTV facilities require various items ofspecialized test and monitoring equipment that are funda-mentally different from those for analog systems. Withoutthe right equipment, the performance verification of equip-ment and systems and, in particular, the diagnosis and rec-tification of errors in digital video, audio, compressed bit-streams, and digitally modulated RF signals will be difficultor impossible. Such equipment types include:

• baseband digital video measurement set;• baseband digital audio measurement set;• transport stream analyzer;• 8-VSB and/or COFDM analyzer;• vector signal analyzer.In addition, since so many digital television systems are

based on computer and IT systems, nearly all the IT diag-nostic and test tools are relevant.

XIV. PROGRAM SERVICE AND MULTIPLEX ARRANGEMENTS

A. DTV Services in ATSC Countries

In the United States, most full-power broadcast televisionstations are associated with one of the national networks(ABC, CBS, Fox, NBC, PBS, PAX, the WB, and UPN).Typically, each station has one main VHF or UHF analogbroadcast channel, although stations in some areas also havetranslators and repeaters. Many state broadcasters associatedwith PBS operate multiple transmitters to cover a wholestate.

During the DTV transition, each station has been allocatedan additional VHF or UHF broadcast channel for digitalservices. As of September 2005, 1508 DTV stations wereon air in 211 U.S. markets, covering the vast majority ofthe population. It is now proposed that analog terrestrialbroadcasting in the United States will terminate on 31December 2008.

Most stations broadcast some programming from theirnetwork feed, some produced locally (primarily news) andsome syndicated programs from other sources. The FCCrequirement is for the program content on the analog channelto be largely replicated in digital, but stations may alsocarry additional digital programs not provided in analog.There is no mandatory requirement for any DTV programsto be in HD. The networks have migrated much of theirprimetime program production to HD and many stationscarry those programs in HD. At this time, most local stationsstill produce their own local news and programming instandard definition.

Except for USDTV,1 all terrestrial DTV broadcastingin the United States is currently unencrypted and free ofcharge.

Multiplex Arrangements: The ATSC broadcast channelcan carry a bit rate of 19.39 Mb/s, which may be allocatedto virtual channels in the multiplex with a variety of combi-nations of HD and SD programs. Stations (or station groups,when owned by a group) make their own decisions onservices to be carried, with typical arrangements as follows:

• one HD program only;• one HD and one SD program;• four SD programs.Other combinations are possible. An additional low bit

rate SD virtual channel is often carried for services such asweather radar, and some stations may allocate some propor-tion of their bandwidth to data broadcast services.

It is common for PBS member stations to vary their pro-gram multiplex at different times, perhaps carrying multipleSD programs during the day and switching to one HD or oneHD and one SD for the evening.

Service arrangements in other ATSC countries are gener-ally similar, although the rollout is less advanced.

1The U.S. Digital Television (USDTV) organization has establishedcooperative ventures with stations in some areas of the country tooffer a subscription service. Each station maintains its own free-to-airHD or SD programming, but allocates a portion of its DTV multiplexbandwidth to additional encrypted SD programs. The additional channelsuse the Windows Media 9 advanced video codec and comprise a totalof 12 programs otherwise available only on cable or satellite.


B. DTV Services in ISDB Areas

The basic concept of ISDB for digital services is that itprovides interoperable broadcasting system and content forvarious physical media such as terrestrial and satellite chan-nels Given the band-segmented transmission for the terres-trial channel and slot assignments for the satellite channel,one can choose the most efficient transmission parameter setfor one segment/slot, or the most robust one for another seg-ment/slot in the same channel. The common feature is theadoption of HDTV for terrestrial and satellite.

ISDB-S digital satellite service started in December2000, providing seven HDTV, three SDTV, and a variety ofsound and multimedia data broadcasting services. In 2007,following the termination of analog HDTV satellite service,digital HDTV satellite broadcasting will be expanded.

DTV terrestrial broadcasting using ISDB-T (simulcastwith conventional analog channels) was started 1 December2003 in the Tokyo, Osaka, and Nagoya, Japan, areas. Otherlocal broadcasters have now started digital transmissions,and it is expected that terrestrial broadcasting will cover60% of households by the end of 2005, and major citiesall over Japan by the end of 2006. It is planned that analogterrestrial broadcasting will be terminated by 2011.

The on-air terrestrial DTV channels provide a full servicefor almost 24 hours a day, and government guidelines requirethat more than 50% of all programs should be pure HD andnot upconverted.

The ISDB-T specifications allow flexible allocation ofbandwidth in a channel for different services. It enablesa maximum of three independent segments for targetinghome reception, mobile reception, and portable reception.Currently each broadcaster provides one HDTV or multipleSDTV services for home or mobile reception.

In 2006, some broadcasters will start to use one seg-ment for a new service for portable reception by handheldterminals and mobile phones. It is expected to create newinteractive broadcasting services, cooperating with othercommunication media.

More information on the service arrangements for ISDBis provided in the related ISDB papers in this special issue.

C. DTV Services in DVB Areas

The DVB standards have been implemented in large areasaround the world. Digital satellite and digital cable servicesusing DVB-S and DVB-C have been available with SDTVprogramming for a number of years. European commercialas well as public service broadcasters are well advancedwith digital SDTV services. The compression system usedin emission has been MPEG-2 MP@ML with bit-rates be-tween 2.5 Mb/s and (more recently) up to 8 Mb/s for SDTV.Bit rates are chosen depending on economic considerations,the degree to which high-quality flat panel displays are inthe public’s hands, acceptable quality, and the availability ofstatistical multiplexing.

Recently, DVB-S2 has been developed for future digitalsatellite transport. DVB-S2 will provide an efficiency im-provement of 30% compared to DVB-S [33].

Digital terrestrial DVB-T is under continuous rollout inEurope. However there are large differences in the timeschedule from country to country, with the most developeddigital broadcasting being in the United Kingdom, whereDVB-T, DVB-C, and DVB-S are now well established. ForDVB-T, there are about 30 television and 20 radio channelsin six Freeview multiplexes. Analog television broadcastingin the United Kingdom is slated to end by 2010. Severalhundred channels are available via DVB-S.

An ambitious DVB-T rollout is in progress in Germany,region by region, with the analog service being switched offwithin months of the start of DVB-T. Digital DVB-T broad-casting began in France in 2005. Other countries have alsobegun digital terrestrial and satellite broadcasting.

Regular HDTV services in Europe will first be broadcastvia satellite utilizing DVB-S2 and H.264 compression. Firstannouncements from cable operators have also been madeto introduce HDTV channels. HDTV via DVB-T is underdiscussion but further investigations and trials are required.Countries that have not yet begun DVB-T SDTV may de-cide to go straight to HDTV. Countries that have alreadystarted with SDTV may decide to use the “digital dividend,”following analog switchoff, for HDTV. However, a com-petitor for spectrum—broadcasting to handheld receivers viaa ruggedized broadcasting system, DVB-H—is also beingconsidered.

More information on the service arrangements for DVB isprovided in the related ISDB papers.

ACKNOWLEDGMENT

Fig. 2 and portions of the text of Section X are extractedand adapted from A Broadcast Engineering Tutorial for Non-Engineers by Graham Jones, published 2005 by Focal Press.The authors would like to thank H. Katoh, NHK, and N. Kat-sura, previously with NTV, for providing information in Sec-tions VI-C and XIV-B about HD origination for DTV inJapan and DTV services in ISDB areas.

REFERENCES

[1] D. H. Pritchard and J. J. Gibson, “Television transmission stan-dards,” in Standard Handbook of Broadcast Engineering, J. C.Whitaker, Ed. New York: McGraw-Hill, 2005, pp. 3.9–3.33.

[2] M. Robin and M. Poulin, Digital Television Fundamentals. NewYork: McGraw Hill, 1998, pp. 131–211, 235–282.

[3] J. Watkinson, The Art of Digital Video. Oxford, U.K.: FocalPress, 2000.

[4] “Studio encoding parameters of digital television for standard 4 : 3and wide-screen 16 : 9 aspect ratios,” Recommendation ITU-RBT.601-5, 1995.

[5] AES recommended practice for digital audio engineering—Serialtransmission format for two-channel linearly represented digitalaudio data, AES Standard AES3-2003, Audio Engineering So-ciety.

[6] International Telecommunications Union, “Parameter values forthe HDTV standards for production and international program ex-change,” ITU Recommendation BT.709-5, 2002.

[7] ——“1280 � 720, 16 � 9 progressively-captured image formatfor production and international programme exchange in the 60 Hzenvironment,” ITU Recommendation BT.1543, 2001.

[8] 10-bit 4 : 2 : 2 component and 4fsc composite digital signals—Se-rial digital interface, SMPTE Standard 259M-1997, Society ofMotion Picture and Television Engineers.


[9] International Telecommunication Union, “Interfaces for digitalcomponent video signals in 525-line and 625-line televisionsystems operating at the 4 : 2 : 2 level of Recommendation ITU-RBT.601 (Part A),” ITU Recommendation BT.656-4, 1998.

[10] Bit-serial digital interface for high-definition television systems,SMPTE Standard 292M-1998, Society of Motion Picture and Tele-vision Engineers.

[11] ——“Standards,” [Online]. Available: http://www.smpte.org/smpte_store/standards/

[12] International Telecommunications Union, International Telecom-munications Union home page [Online]. Available: http://www.itu.int/home/index.html

[13] Audio Engineering Society [Online]. Available: http://www.aes.org/publications/standards/list.cfm

[14] Consumer Electronics Association [Online]. Available:http://www.ce.org/standards/StandardsCatalog.aspx

[15] IEEE [Online]. Available: http://www.ieee.org[16] Society of Cable Telecommunications Engineers [Online]. Avail-

able: http://www.scte.org/content/index.cfm?pID=59[17] B. Fox, “The digital dawn in Europe [HDTV],” IEEE Spectr., vol.

32, no. 4, pp. 50–53, Apr. 1995.[18] H. Hoffmann, D. T. Itagaki, and D. Wood, “HDTV revis-

ited—User requirements and opportunities,” presented at the 146thSMPTE Tech. Conf, Pasadena, CA, 2004.

[19] European Broadcasting Union, “High definition image formats fortelevision production,” EBU Tech. 3299-2004.

[20] ——“The potential impact of flat panel displays on broadcast de-livery of television,” EBU Tech. Inf. I34-2002.

[21] ——“Further considerations on the impact of flat panel home dis-plays on the broadcasting chain— First edition,” EBU Tech. Inf.I35-2003.

[22] ——“EBU guidelines for the RRC-06,” EBU Tech. Inf. I37-2005.[23] ——“Maximizing the quality of conventional quality broadcasting

in the flat panel environment,” EBU Tech. Inf. I39-2004.[24] ——“EBU statement on HDTV standards,” EBU Tech. Rec. R112-

2004.[25] —— [Online]. Available: http://www.eicta.org/[26] Audio and film—Time and control code, SMPTE Standard 12M-

1999, Society of Motion Picture and Television Engineers.[27] Formatting AES/EBU audio and auxiliary data into digital video

ancillary data space, SMPTE Standard 272M-2004, Society ofMotion Picture and Television Engineers.

[28] Dolby Laboratories, “Dolby E multichannel audio coding,”[Online]. Available: http://www.dolby.com/assets/pdf/tech_li-brary/49_Dolby_E_Innovation.pdf

[29] Society of Motion Picture and Television Engineers, “Taskforce for harmonized standards for the exchange of programmaterial as bitstreams, final report: Analysis and results, 1998,”[Online]. Available: http://www.smpte.org/engineering_commit-tees/pdf/tfrpt2w6.pdf

[30] B. Devlin, “MXF is ready for you, are you ready for it?,” in Proc.NAB Broadcast Engineering Conf. 2005, pp. 438–443.

[31] O. Morgan, “Metadata system architecture,” in Proc. IBCConf. 2002 [Online]. Available: http://www.broadcastpa-pers.com/IBC2002/ibc2002.htm

[32] Vertical ancillary data mapping for bit-serial interface, SMPTEStandard 3342M-2000, Society of Motion Picture and TelevisionEngineers.

[33] D. Breynaert and M. d’Oreye de Lantremange, “Analysis of thebandwidth efficiency of DVB-S2 in a typical data distribution net-work,” presented at the CCBN 2005, Beijing, China.

Graham A. Jones was born in Stoke-on-Trent,U.K., in 1944. He received the B.Sc. degree inphysics from Nottingham University, U.K., in1964.

He started his career with the BBC and for 18years was a partner of International BroadcastingConsultants. Previously with Harris Corporation,he was Engineering Director for the Harris/PBSDTV Express road show. He is currently Directorof Communications Engineering with the Na-tional Association of Broadcasters, Washington,

DC, working on advanced television issues, standards, and education. He isauthor of A Broadcast Engineering Tutorial for Non-Engineers (Elsevier,2005), and editor for the forthcoming 10th NAB Engineering Handbook.

Mr. Jones is a Fellow and Governor of the Society of Motion Pictureand Television Engineers. He is a Chartered Engineer and a member ofthe Institution of Electrical Engineers, the Society of Broadcast Engineers,and the Royal Television Society. He was chair of the ATSC TSG/S1 spe-cialist group on PSIP Metadata Communications and chairs the SMPTE S22working groups on lip sync and image formatting. In 2004 he received theATSC Bernard J. Lechner Outstanding Contributor Award.

James M. DeFilippis (Member, IEEE) was bornin Morristown, NJ, on January 27, 1958. Hereceived the B.S. and M.S. degrees in electricalengineering from the School of Engineering,Columbia University, New York, in 1980 and1990, repsectively.

He has worked in radio and television broad-casting for 25 years, including the ABC radio net-work, the ABC television network, the AdvancedTelevision Test Center, and the Atlanta OlympicBroadcast Organization. Currently he is Senior

Vice President of Television Engineering for the Fox Technology Group,Los Angeles, CA. His primary research focus is on new video and audiocompression systems.

Mr. DeFilippis is a member of SMPTE and is involved in standards de-velopment at the International Telecommunications Union.

Hans Hoffmann (Member, IEEE) was born inMunich, Germany. He received the EngineeringDiploma from the University of Applied Sci-ences, Munich, in 1992.

He joined the Insitut fuer Rundfunktechnik(IRT) in 1993 as a Member of the ResearchStaff in new television production technologies.In 2000 he moved as Senior Engineer to theTechnical Department, European BroadcastingUnion, Geneva, Switzerland. For the last threeyears, he has been involved in the EBU technical

activities on high definition in television production and emission. He haschaired the EBU project groups P/BRRTV and P/PITV, both involved innew technology innovations in television.

Mr. Hoffmann is a Fellow of the SMPTE and a member of SID and FKT.He was chairman of the SMPTE technology committee N26 on Networksand File Management and in 2002 became SMPTE Engineering Director,Television and chair of the Television steering committee.

Edmund A. Williams (Senior Member, IEEE)was born in Cleveland, OH, in 1939. He receivedthe B.S. degree in communications engineeringfrom Franklin University, Columbus, OH, in1961.

His professional career has been in publicbroadcasting engineering positions since 1958,and he retired from the Public BroadcastingService in 2004. He developed and conductedtechnical seminars on the 40-city nationwide tourof the Harris/PBS DTV Express. He is author

of numerous technical publications and editor-in-chief of the 10th NABEngineering Handbook.

Mr. Williams is a member of the IEEE Broadcast Television SocietyAdCom and Broadcast Symposium committee; he received the ThirdMillennium Medal in 2000, and is a member of the Association of FederalCommunications Consulting Engineers, the Society of Motion Picture andTelevision Engineers, Society of Cable Telecommunications Engineers,and the Society of Broadcast Engineers.


Documents

Digital Television Station and Network …For SD DTV, the choice of digital video format is usually based on the number of lines of the legacy analog system used in that country. Countries