video testing in a dtv world

In the days of composite analog television systems, a verylimited set of video signal types was used throughout theproduction and distribution chain. A modern digital televi-sion system is much more complex, often requiring conver-sion of the video signal into a variety of signal types includ-ing nonlinear compressed forms. A simplified block diagramof a modern television system is shown in Fig. 1.

Program content production primarily uses baseband ana-log and full bandwidth digital signals for ease of contentmanipulation. However compressed video using MPEG-2,Motion JPEG, or DV is widely used for disk and tape stor-age, providing excellent quality results in a cost efficientmanner.

Following program production, the television signal maybe compressed for storage, efficient transmission, or intrafa-cility interconnection in digital form. Typically this will beMPEG compression resulting in an MPEG transport stream(MTS) which is then multiplexed with other MPEG trans-port streams for transmission or interconnection. Statisticalmultiplexing is often used for multiple programs providingthe most effective use of the available digital bandwidth.

The broadband telecommunication system provides avariety of transmission methods. Traditionally these havebeen voice-channel oriented with special data mapping fordigital television signals. Use of asynchronous transfermode (ATM) hides such formatting from the user. In orderto provide the quality of service expected for broadcastoperation, forward error correction (FEC) is generallyrequired. A number of different modulation methods areused for radio frequency (RF) transmission over cable, satel-lite, and terrestrial systems. FEC is always used to providethe required quality of service RF transmission.

At the receive end of a transmission system, the desiredprogram is demultiplexed from the MTS and the programdata is decompressed. One of the advantages of compressionis the capability of providing different video picture qualitylevels based on bit rates. Distribution quality to the homemay be adequate with bit rates of 2 to 5 Mbits/sec for stan-dard definition television (SDTV) and 15 to 19 Mbits/sec forhigh-definition television (HDTV). Contribution quality isrequired if further production processing is planned for thereceived signal. In that case, bit rates of 18 to 50 Mbits/secare required for SDTV and 100 to 300 Mbits/sec for HDTV.

Video testing in the digital television system is not just amatter of developing new techniques for the difficult nonlin-ear compression process. A significant portion of the sys-tem still uses analog and full-bandwidth digital signalsrequiring application of traditional analog and recentlydeveloped digital test methods.

Testing LayersThere are three major testing layers as shown in Fig 2.

Baseband video consists of such signals as traditional analogNTSC or PAL video; component digital SDTV, as defined byITU-R BT.601; and digital HDTV, as defined by ITU-RBT.709. Video quality is measured in two ways, signal qual-ity and picture quality, as described next.

At the intrafacility level there are two aspects to consider:compression method and physical interconnect. MPEG-2 isone compression method within a program provider facility;however, it is commonly used in at least two forms: elemen-tary streams or transport streams with PES streams and pro-gram streams additional possibilities. DV is another com-mon compression method for both SDTV and HDTV pro-gram production. At this layer it is the formatting protocol ofthe compressed data and its mapping into the physical inter-connection that are to be tested. Certainly the electrical oper-ation of the interconnection must be maintained as well.However, this is usually accomplished with sufficient head-room to provide a completely error-free environment for allintrafacility interconnections. Common physical interconnec-tions are:

Serial digital interface (SDI) for both SDTV1 andHDTV.2

Serial data transfer interface (SDTI)3 using the samephysical interface as SDI.

SMPTE 310M4 a robust synchronous serial interface forATSC transmitters.

Asynchronous serial interface (ASI)4 operating at thesame bit rate as SDTV SDI but using a different channelcode.

Broadband digital networks and RF methods are used forinterfacility transmission. Traditionally various proprietaryand standard RF methods with powerful error correctionhave been used. More recently mapping the compressed datathrough an ATM layer or directly into PDH or SDH trans-port protocols with or without error correction is becomingmore common. DVB6 and ATSC7 systems are most com-

SMPTE Journal, 2000 1

Video Testing in a DTV WorldBy David K. Fibush

This paper describes the digital television system, its elements, and appropriate methods ofvideo testing. A layered approach is defined including video, protocol, and transmission chan-nel testing. With todays use of video compression there is still a need for traditional analog andfull bandwidth digital testing methods. Compression systems require objective picture qualitymeasurements of distortions caused by its nonlinear and time-variant digital processing. Testmethod terms such as in-service and realtime are defined for both video and protocol testing.The three internationally accepted system approaches to objective picture quality testing arediscussed including the advantages and disadvantages of each.

Presented at the 34rd SMPTE Advanced Motion Imaging Conference (paper no. 33-S-3), in San Francisco, CA, February 3-5, 2000. David Fibush is with Tektronix Inc.,Beaverton, OR. Copyright 2000 by SMPTE.

monly used for consumer television terrestrial, satellite, andcable applications. They are both based on MPEG-2 datawith different forms of information tables and RF modula-tion methods.

Video testing requirements for each application in theproduction and distribution of digital television programs isbased on the testing layers appropriate for its part of the sys-tem. Program providers will be most interested in videoquality and intrafacility interconnection operation, whiletransmission service providers will be most interested inerror conditions of the channel. However, video qualityparameters are important to all users as the ultimate test ofproviding the program to the final viewer. Although abroadband service provider might be most interested in errorrates and ATM cell loss ratios, it is the effect they have onvideo quality that will be the topic of discussion with the adagency that paid for the commercial. Similarly the programcontent provider will discuss guaranteed cell loss ratioswhen selecting a provider for interfacility transmission for adistributed studio design.

Video Test Method TermsVideo systems are intended to display a picture that accu-

rately represents the scene being scanned by the camera.

With todays special effects capabilities, the displayed pic-tures may differ in an artistically defined manner from theoriginal. Nonetheless, at some point in the processing, wherethe artistic changes are complete, the resulting pictures areto be accurately conveyed to the user with the desired quali-ty. There are a number of terms that are used to describevideo test methods:

It is important to note that each pair of terms is indepen-dent of the other pairs. As an example, in-service testingcould use either direct or indirect methods, and it could beeither real or non-realtime. Realtime tests may be either con-tinuous or sampled.

Analog video and uncompressed digital video are evaluat-ed using traditional signal quality tests. These are indirectwith respect to the pictures passing through the system. Thatis, they measure channel response to a series of differenthigh-quality test signals. Indirect tests are based on thepremise of a time invariant linear system. Video distortions

2 SMPTE Journal, 2000

Figure 1. Digital television simplified block diagram.

ChannelCoding

andError

Protection

System Coder and Multiplexer

System Demux and Decoder

VideoD/A

ChannelDecoding

and Error

Correction

Cable, Satellite,Terrestrial

QAM, COFDM,VSB, QPSK

Conversionto display

format

Audio D/A

RFModulator

ChannelDeformat

ChannelFormat

[optional errorcorrection]

[optional errorprotection]

RFDemod

Video:Analogor Digital

Audio:Analogor Digital

Analog VideoDigitalVideo

Compressed TelevisionVideo (Audio, Data)

Program Content Production

Baseband Audio/Video

Standard/High Definition

Compressed: MPEG, DV

DigitalAudio

OtherSimilarChannels

Other Similar Channels

Other Similar Channels

TransportStream

TransportStream

OtherSimilar

ChannelsMUX

DEMUX

Analog Audio

Data,Control

VideoCoder

Demultiplex

Coding[error protect]

Digital StorageMedia

Decode[error correct]

DecodeA/V/D

PES

PES = packetized elementary streamStat MuxControl

PES = packetized elementary stream

AudioCoder

Compressed Television Tape Recorder

Data/Control

Packetizer MuxPES

ATM virtual channel on shared network

Point-to-point connection: DS-1, E-3, DS-3, SDH/Sonet

Signal quality (indirect) Picture quality (direct)In-service Out-of-service Realtime Non-realtime (deferred time)Continuous Sampled (or scanned for

multiple programs)

produced may be accurately determined by passing suitabletest signals through the same system.

Digital compression systems are nonlinear, hence theresulting video quality will be a function of the picture con-tent and other time varying attributes of the system (e.g., sta-tistical multiplexing). Test signals are easily compressed,hence their changes through a system are not a meaningfulmeasure of video quality. Therefore, direct testing of picturequality is required in addition to the signal quality measure-ments for the linear parts of the system. Direct evaluation ofthe system is based on quality changes between the video atthe selected test point and the video at the source. The sourcevideo may be either a variety of defined (preferably standard)program-like picture sequences or general program material.

Note: the term picture quality is actually picture degra-dation through the system and does not imply the intrinsicquality of the picture. Beauty is in the eye of the beholderand not something we can measure.

In-service tests are made while the program is being dis-played, directly by evaluating the program material, or indi-rectly for linear systems, by including vertical interval testsignals with the program material. Out-of-service, appropriatetest scenes are used for direct tests (picture quality) and fullfield test signals are used for indirect tests (signal quality).

Realtime testing provides results shortly after the videohas been processed by the system where shortly is deter-mined by the user requirements for the test. An examplewould be differential phase and gain measurements aver-aged over several fields using a Tektronix VM700T. Formany applications, such as MPEG-2 transport stream proto-col, verification, or high accuracy picture quality measure-ment, deferred time testing is appropriate to allow a more

detailed analysis from data stored on disks.In the application of realtime testing, it may be necessary

to use a sampled approach where only certain time incre-ments or samples of the data are analyzed due to the com-puting power required. This might also be used where sever-al programs are scanned one after the other providing a sam-ple of data for that program. Testing methods that are lesscomplex can be accomplished in realtime based on a contin-uous stream of data.

Analog Video TestingMeasurement practices for analog television systems are

well defined and very reliable.8,9 They are based on the lin-ear system premise that video distortions produced in a sys-tem may be accurately determined by passing suitable testsignals through the same system. However, a series of dif-ferent tests are required to verify that the system will pro-duce acceptable pictures. One test will not do the job.

A minimum set of tests for an analog system might be:luminance amplitude, rise/fall times, bandwidth, groupdelay, signal-to-noise ratio, and waveform nonlinear distor-tions. For composite systems (PAL/NTSC): chroma ampli-tude, chroma phase, differential phase, and differential gainare also important. A matrix of tests and specifications canbe associated with different qualities of video signal trans-mission, but no one number or mathematical combination ofparameters will describe the resulting system operation. Ifadjustments are made, there is quite often interactionbetween processing elements resulting in changes of severalmeasurement parameters. A television engineer must evalu-ate the combined results of the various tests as well asobserve the resulting picture.


Figure 2. Digital television testing layers.

ProgramCoding/Compression

TransmissionCoding

(gateway)

Program

Intra-Facility Data Stream

Inter-Facility Data Stream

Signal Test Function

BasebandNTSC, PAL,

Digital SDTV, HDTV

Compressed Data

Physical InterconnectDV, MPEG-2 TS, ES

SDI, SDTI, ASI, SMPTE 310M

RF Digital Data

Broadband Digital DataQPSK, 8-VSB, 64/256QAM

PDH, SDH, ATM

Video QualitySignal Quality

andPicture Quality

ProtocolUncompressed Video,

Compressed Data,Timing Errors,

Interconnect Mapping

TransmissionChannelAnalysis

Full-bandwidth Digital Video TestingEven with the rapid rise in the use of compression tech-

niques, full-bandwidth digital television will continue to bea major element in television systems. Processing andinterconnecting video in digital form eliminates most sig-nal quality loss problems of an analog system. As the tele-vision industry transitions from analog to digital video,combinations of composite and component systems arebeing used; however, the preference is for all-componentvideo operation.

For operational purposes, monitoring of equivalent ana-log video signal properties is based on a signal processedfrom the digital data. Where testing of the analog signalrequired only that various parameters be measured on asingle waveform digital testing requires three types ofanalysis: digital signal coding, digital data formatting, andparameters relating to the digital waveform. Although allthree measurement types can be performed with a singleinstrument, such as the Tektronix WFM 601M, there is sig-nificant processing between each pair of layers with differ-ent analysis methods for each layer as well.

Correct coding of the signal, with respect to the stan-dard, can be determined by a waveform display of theresulting analog signal and a readout of corresponding dig-ital values in defined areas such as black, peak white, zero-color, maximum color excursions, and non-use of certainexcluded digital values. Digital formating of the nonvideopart of the signal can be quite complex particularly whendigital audio is embedded in the digital video signal.Measurement includes displaying an analog rendition ofthe formatting digits, cursor selection of each sample for areadout of the digital value, as well as a logic-analyzertype display of a selected group of digital words.

Included in the digital formatting are error detectioncyclic redundancy check (CRC) words that can be used inmonitoring or operational equipment to determine if thedigital signal at a receiver exactly matches that of the send-ing equipment, where the CRCs were inserted. CalledEDH, for error detection and handling, this method pro-vides an accurate way to determine the onset of errorswhen a stressing method is used to measure operationalheadroom in the virtually error-free environment of serialdigital video.

Analysis of the serial digital waveform (which is reallyan analog signal) is, perhaps, the most complex of the threemeasurement types. An eye pattern display is used to mea-sure basic parameters such as amplitude, rise time, andovershoot. The eye pattern can also measure jitter if theclock used to produce the eye pattern is carefully specified.In a typical serial digital television waveform monitor, eyepattern determination of jitter would require setting of cur-sors to make the measurement; however, numeric measure-ment values may be quickly obtained using a demodulatormethod. In many cases operational headroom for a serialdigital video signal is simply related to the amount of coaxin the transmission path and the amplitude of the launchsignal. A measurement of these parameters can be derivedat the receiver end based on an assumed type of coaxthereby providing some important headroom information.

Picture Quality Test MethodsTelevision programs are produced for the enjoyment or

education of human viewers so it is their opinion of thequality that is important. Formal subjective tests as definedby ITU-R BT.50010 have been used for many years. Withthe advent of digital video compression, the number of dif-ferent test methods in BT.500 have increased every year.

Advantages of subjective testing are: a test may bedesigned to accurately represent a specific application; validresults are produced for both conventional and compressedtelevision systems; a scalar mean opinion score (MOS) isobtained; and a wide range of still and motion picture appli-cations are accommodated.

Weaknesses of subjective testing are: a wide variety ofpossible methods and test element parameters must be con-sidered; meticulous setup and control are required; manyobservers must be selected and screened, and complexitymakes it very time consuming.

The result is subjective tests are only applicable for devel-opment purposes; they do not lend themselves to opera-tional monitoring, production line testing, trouble shooting,or repeatable measurements required for equipment specifi-cations.

The need for an objective testing method of picture quali-ty is clear, subjective testing is too complex and providestoo much variability in results. However, since it is theobservers opinion of picture quality that counts, any objec-tive measurement system must have good correlation withsubjective results for the same video system and testsequences.

With a new paradigm such as compressed digital video,subjective test methods were used before objective test meth-ods became available. Certainly subjective test methods arethe starting point for evaluating objective test methods.However, it is an objective test method that provides accuratemeasurements, with proven correlation to subjective assess-ments, which will be the benchmark for development of testmaterials and calibrating less capable objective methods.

There is general agreement in the industry that there arethree methodologies for objective picture quality measure-ment that provide three levels of measurement accuracy.11,12They are identified as:

Complete source video (also called Picture comparisonand mow officially known as Full Reference).

Reduced source video information (also called Featureextraction and now officially known as Reduced Reference).

No source video (also called Single-ended and now offi-cially known as No Reference).

The first two methods are double-ended, that is the actualsource video, an exact copy of the source video or somereduced information extracted from the source video mustbe available to the instrument making the picture quality cal-culations. (Note: Source video is sometimes called referencevideo. In this paper the term source is used since refer-ence might imply a defined video sequence whereas qualitywill often be determined based on program video.)

Picture comparison makes a measurement of picture qual-ity (degradation) using the full source video and the videoprocessed by the system under test as shown in Fig. 3. It


uses a matrix-based mathematical com-putation to process each picture orsequence of pictures. The resulting datarepresents a filtered version of the pic-tures containing an amount of data simi-lar to the original pictures. Typically, thepixel-by-pixel difference between fil-tered versions of the source and degrad-ed pictures is used to determine anobjective quality score. This is the mostaccurate method because it has completeinformation about the changes in the pic-tures and generally uses a very sophisti-cated computation algorithm based on a model of the humanvision system including temporal and color response.

Knowledge of compression or other processing applied tothe video is not required. Although a primary application ofthis measurement method is for codec evaluation using stan-dard test sequences it can be used in-service for monitoringof statistical multiplexer operation or at a remote location ifa copy of the source material is available. Realtime continu-ous operation is not precluded although significant computepower is required.

It is the sophisticated processing algorithm that gives thepicture comparison method an accuracy superior to the othertwo methods. Because the complete source video is availableanother less sophisticated calculation can be made. Peak sig-nal-to-noise ratio (PSNR)13 has traditionally been used forevaluating differences between a source and processed pic-ture. Although it is known to produce inconsistent results onsequences with different complexity of spatial and temporalpictures, it is a useful benchmark. It has been shown to havegood accuracy for pictures with low degradation and can beused to locate small differences between pictures that wouldnot necessarily be seen by a human observer.

Unfortunately, the convenience of performing measure-ment level picture quality evaluation anywhere in the sys-

tem, albeit by indirect means, is not available for com-pressed systems as it is for uncompressed linear systems.There are two approaches to this situation.

First, since the video is being carried throughout the sys-tem as digital data, if the bits dont change and the timing ofthe transmission is held within given limits, the video and itsquality will not change either. Intrafacility transmissionlinks are error free if operating properly.

For broadcast applications, interfacility transmission linkswill use forward error correction (FEC) to provide the sameerror free operation. Even video conferencing transmissionlinks are expected to have quite low error rates and usesophisticated error concealment.14 In this case, measurementof picture quality at the original encoding location providesthe necessary quality information. For satellite transmission,the link can be included in the measurement by providingthe picture comparison measurement instrument with down-link video as the processed video at the uplink location.

The second approach is the use of known videosequences. Application of standardized reference video testsequences15 allows out-of-service picture comparison evalu-ation of system performance at a location remote from theinput video source. Standardized video sequences or anypredetermined video sequence of the users choice (perhaps


EncoderSourceVideo

ProcessedVideo

Objective PictureQuality Rating

Decoder

MeasurementSystem

Digital Transmission Link

Figure 3. Picture comparison test method.

Processed Video

EncoderModulate

&Upconvert

DecoderDemod

Cable Head-end

Storedsource

video SourceVideo

SourceVideo

PQRmeasurement

system

PQR's

Figure 4. Example of remote PQR measurement.

6a show-opening moving graphic) can also be used as thesource video for the measurement. An example is mea-surement of picture quality rating (PQR) for a cable head-end (Fig. 4). Another very important benefit of using stan-dardized reference video sequences is that they enable themanufacturer and purchaser of equipment for compresseddigital television to understand and measure performancespecifications using common material.

Feature extraction (Fig. 5), uses a mathematical computa-tion to derive characteristics of a single picture (spatial fea-tures) or a sequence of pictures (temporal features). Thisusually results in an amount of reference data per picturethat is considerably less than used to transmit the com-pressed picture. The calculated characteristics of the sourceand degraded pictures are then compared to determinechanges in the pictures related to the type of featuresextracted. This provides a measure of picture impairments.In this low reference data mode, incorrect video, lost frames,and other types of errors not necessarily due to the compres-sion process, can be detected.11 To facilitate application ofthe feature extraction method, a special MPEG-2 transportstream PID (packet identification) has been defined by theDVB to carry the reference data.

By using a relatively high level of reference data, perhapsas much as the compressed picture, a useful objective picture-quality calculation can be made. Knowledge of compressionor other processing applied to the video may be used to deter-mine what features are to be extracted in order to increase themeasurement accuracy of the calculation. Because bits equalcost, applications for feature extraction are primarily for mon-

itoring inconsistencies of pictures sentand received through a transmission sys-tem as described above.

Single-ended testing is the most appro-priate method for picture monitoring(Fig. 6). Based on knowledge of the com-pression system being used, theprocessed video canalyzed for artifactsand other defects. The most commonartifact to be detected is blockiness, aresult of the discrete cosine transform(DCT) compression system used byMPEG-2 and DV. As the compressionsystem works harder, due to either morecomplex program material or less bitsavailable for data, more blockiness willbe generated. The higher the level ofblockiness the greater the picture degra-dation for a given source video sequence.

Much like PSNR, this method doesnot provide strong correlation with sub-jective picture-quality assessment over avariety of video sequences. Nonethelessit has some significant operationaladvantages. Since no information fromthe source video is required, the single-ended monitor may be placed anywherein the system. Detection of picturedefects is not limited to compressionartifacts; a measure of gaussian noisewould be an example. This could be use-

ful at a compression encoder input to increase coding effi-ciency and resulting picture quality.

Compute power required for the test is modest allowingan economic approach to multichannel operation. Artifactlevel detection can be used as a trigger to warn of possiblequality problems. A log of detected artifacts versus time canbe a valuable system trouble-shooting tool.

Protocol Test MethodsIntrafacility transmission links require several different

sublayers of testing and the extended application of digitalanalysis techniques. Although there are a variety of inter-connection methods and types of data to be carried, each isdefined in specifications developed by standards organiza-tions. While protocol testing is the primary type of analysisto be performed there are other sublayers to be considered:

1. Protocol analysis of formatting and compliance to stan-dards of uncompressed video and included ancillary data.Compressed programs in such formats as MPEG-2 elemen-tary streams (ES), transport streams (TS), and programstreams (PS); DV-based data streams; and physical layerdata mapping of SDTI and ASI.

2. Physical layer electrical characteristics, waveform typespecifications for SDI, ASI, and SMPTE 310M.

3. Timing errors due to interfacility transmission links: jit-ter and wander in received data timing information and itterand wander in baseband video resulting from the timinginformation.

4. Response to custom data streams.

SMPTE Journal, 2000

EncoderSourceVideo

ProcessedVideo

ImpairmentParameters

ReferenceData

Decoder

FeatureExtraction &Comparison

FeatureExtraction


EncoderSourceVideo

ProcessedVideo

ImpairmentParameters

Decoder

MonitoringSystem


Figure 5. Feature extraction test method.

Figure 6. Single-ended test method.

There are a number of terms are used to define the testmethods. They are similar to those used for video testing butare restated here as applicable for protocol testing:

Realtime testing is primarily a monitoring function wherekey characteristics of one or more data streams are analyzedto determine if they meet required specifications. Deferred-time testing is implemented by storing a data stream andgenerally performing an extensive in-depth protocol analy-sis. Realtime testing may include timing analysis, whereasthe storage of the data for deferred-time testing usually doesnot provide any timing information.

Continuous testing is the preferred method for realtimemonitoring. This means that every set of data, such as TSpackets, are analyzed to a level of detail allowed by thecompute power available. Sampled testing would only ana-lyze a selected subset of data. This could be due to a lack ofcompute power to analyze every packet or due to scanningof multiple channels where increments of time for analysisare allocated to each channel.

In-service tests have no specific limitations as are incurredwith video quality testing. The data may be analyzed whileprograms are being transmitted at any location in the systemand in a single-ended manner. The only limits relate to com-pute power for realtime and continuous monitoring as dis-cussed above. Out-of-service testing is also an importantaspect for maintaining DTV systems but the emphasis is oncustom streams, such as TS, to determine system response toknown valid or specifically invalid data sets.

ConclusionThis paper has given an overview of video test methods

including protocol analysis of the compressed data stream.Traditional test methods continue to be important for theanalog and full bandwidth portions of todays hybrid sys-tems of compressed and uncompressed video. The systemapproach to a number of objective picture quality and dataprotocol test methods has been described. While individualtest methods are important, it is their integration into aQuality of Service monitoring system that will provide thegreatest overall benefit to maintenance of digital televisionsystems.

References1. Rec. ITU-R BT.656-4, Interfaces for Digital Component Video Signals

in 525-line and 625-line Television Systems Operating at the 4:2:2Level of Recommendation ITU-R BT.601 (Part A).

2. Rec. ITU-R BT.1120-2, Digital Interfaces for 1125/60and 1250/50HDTV Studio Signals.

3. Rec. ITU-R BT.1381, SDI-based Transport Interface for CompressedTelevision Signals in Networked Television Production Based on Rec.ITU-R BT.656 and ITU-R BT.1302.

4. SMPTE 310M, Synchronous Serial Interface for MPEG-2 DigitalTransport Streams, SMPTE J., 107:274, Apr. 1998.

5. DVB A010, Interfaces for CATV/SMATV Headends and SimilarProfessional Equipment.

6. DVB standards are published by ETSI, go to http://www.etsi.org andaccess Publications and Products then Publications DownloadArea then search for DVB.

7. http://www.atsc.org.8. Television Measurements for NTSC Systems, Tektronix Inc., Beaverton,

OR, 1994, Lit No. 25W-7049-3.9. Television Measurements for PAL Systems, Tektronix Inc., Beaverton,

OR, 1994, Lit No. 25W-7075-1.10. Rec. ITU-R BT.500, Methodology for the Subjective Assessment of the

Quality of Television Pictures.11. J. Baina and G. Goudezeune, Equipment and Strategies for Service

Quality Monitor-ing for Digital Television Networks, SMPTE J.,108:632, Sept. 1999.

12. ITU-T Study Group 9 Draft Rec., J.OVQ, April 1999.13. ANSI Standard T1.801.03-1996, Digital Transport of One-way Video

Signals, Parameters for Objective Performance Assessment.14. Draft Standard on Quality of Service for Business Multimedia

Conferencing, T1A1.5/99-201, www.t1.org/index/0629.htm.15. Rec. ITU-R BT.802-1, Test Pictures and Sequences for Subjective

Assessments of Digital Codecs Conveying Signals Produced Accordingto Rec. ITU-R BT.601. (Note: The sequences are available fromSMPTE.)

The AuthorDavid Fibush has been involved in television engineering

for more than 30 years. He was a major contributor to stan-dardization of the SMPTE Type C format and developmentof television recorders for various tape formats.

At Tektronix, Fibush was involved in the development oftest signal generators and video frame synchronizers andthe planning of compressed television testing products.Presently, he is a consultant to Tektronix in the area ofvideo quality testing for compressed television systems.

Fibush is a SMPTE Fellow and Chairman of theCommittee on Video Compression Technology. In 1995, hereceived the SMPTE Progress Medal, which recognizesoutstanding technical contributions to the progress of engi-neering phases of the motion picture and/or televisionindustries.


Realtime Non-realtime (deferred time)Continuous Sampled (or scanned for multiple

programs).In-service Out-of-service

video testing in a dtv world

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