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SMPTE  Historical Note    JUNE  1981
 1_ NTSC: Introduction
 2_ Scanning, Timing/Sync, Sync Recovery,  Numbers
 3_ Gain & Offset, D.C. Restoration, Gamma Correction
 4_ Resolution, Bandwidth, Spectrum
 5_ Color Physics: Eye, CIE
 6_ Color Encoding: Color Bars, Camera, RGB, YIQ, Color  Subcarrier
 7_ Color Decoding:
 8_ Digital TV/Graphics: ADC-DAC, Frame Buffers, Timebase Correction, VGA
 9_ VCR: Spectrum, Circuits
10_ Circuits & Practices: D.C. Restore, Proc Amps, DAs
---Related Technologies
Automated Target Scoring
Automotive Lane Tracker
Colorwheel Camera
LINKS:
Suggested Texts:
Television Engineering Handbook,  Benson Rev Ed. Mc Graw Hill
Video Demystified, K. Jack (Brooktree's Guru) Hightext
Basic Television and Video Systems, Grob, Bernard  Mc Graw Hill
The Forces at Work Behind the 
NTSC Standards
By DONALD G. FINK
 
  --Introduction
-Monochrome Television--The First NTSC:  Two Previous RMA Committees
----Formation of the First NTSC

-The Color Television Wars:  Incompatible Versus Compatible Systems
----Second Calling of the NTSC
----Principles Adopted in 1953
----Turn of the Tide

-The Impact of NTSC on the World: Difference between NTSC, PAL, and SECAM
----Some Possible Improvements of the NTSC Standards
----Outlook on the Future
 

Visit: williamson-labs.com  for Electronics Tutorials
www.PixelSmart.com is a frame grabber manufacturer. They also make video overlay boards, chroma key boards and many other digital video effects boards.  ( PixelSmart also performs contract work ) 
To: willimson-labs.com/-
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LINKS

  • Broadcast Net
  • CableLabs 
  • Computer Dynamics - Flat panel displays
  • Cornell Theory Center  Animation on Videotape
  • Delta Beta Pty. Ltd. - Video On Demand
  • Doug Lung's RF Technology 
  • DVDO digital video
  • EPI - Electronic Imaging
  • EPIX Vision - Image acquisition,
  • e-VideoTV Inc. - Video-on-demand
  • FCC
  • NAB - National Association of Broadcasters
  • SBE - Society of Broadcast Engineers
  • SMPTE
  • SMPTE QuickGuide 
  • SPIE - The Intl Society for Optical Engineering
  • Elantec Semiconductor
  • Gennum Corp
  • Harris Corp Broadcast Division
  • Philips Semiconductors
  • PixelSmart  Frame Grabber Cards
  • TI - CCD  Image Sensor Products

  •  
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  • Marshall Electronics - CCDs, etc.
  • Polaris Industries CCD & CMOS Cameras
  • VISIONTECH - Cameras, etc.
  • Interactive Color Wheel - Java applet 
  • IOT Tube Replacement
  • ITVA - International Television Association
  • The Joe Fedele Page - Broadcasting Technology
  • Joe Kane's Video Essentials
  • Video Demystified  -- Book *
  • MZTV Museum TV History
  • NTSC-TV - Tutorials on TV Basics & more. 
  • Philips Digital Video Systems
  • Projectavision - DV Projection
  • The Pro-MPEG Forum
  • Snell Wilcox Broadcast equipment
  • Tektronix, Inc. - Video Measurement Tutorials
  • Testcards - TV Testcards,
  • Texas Instruments Digital Light Processing   DLP
  • TGS Engineering
  • Tomi Engahl's Video Tech Page - *
  • TV Technology - The on-line magazine
  • Video Engineering - Charles Poynton
  • Video University Engineering Primer
  • Williamson-labs - Tutorials
  • Computer Bits magazine Article "Computers ver TV." 

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    -Introduction:
    The work of the first NTSC (National Television System Committee) was built on the basis of earlier standardization attempts.  The first NTSC laid the foundations that made monochrome television a practical reality in the United States.  The standards it endorsed in 1941 are still in use today.  At the dawn of color television it seemed at first that it was not going to be compatible with monochrome television and would need special receivers.  A tug of war of compatible versus incompatible color television systems ensued.  The compatible system won.  The second NTSC set up the compatible standards that have been adopted by the U.S. and by the rest of the world in many major respects.

    Casual observers of technical progress often assume that the basic forces at work are merely those of new science and improved technology.  But seasoned veterans of the technical wars know that many other forces are also at work.  Prominent among them are the pride and prejudice of technical, industrial, and political leaders; the pursuit of power and profit; the rivalry for command of patents and markets; as well as the forces of government: inertia, misunderstanding, and, occasionally, foresight. The development of television in the United States is a prime example of the conflicting interplay of these forces and their ultimate resolution for the public good.  The body on which these forces were principally brought to bear was the National Television System Committee. 

    Its initials "NTSC" are the hallmark of American television practice and, for that matter, the hallmark of much worldwide practice.

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    A paper presented at the 122nd annual SMPTE Technical Conference, November 9-14, 1980, New York, N.Y. AUTHOR: Director Emeritus of the IEEE and Chairman of the SMPTE Study Group on High-Definition Television.

    Monochrome Television
    The First NTSC

    Two Previous RMA Committees

    The first NTSC reviewed in 1940 and 1941 the existing arts of television and brought forth standards which were thereupon promptly adopted by the FCC (Federal Communications Commission) as the basis of the black-and-white service.  Most of the new science and technology involved had been worked out previously by two committees of the RMA (Radio Manufacturers Association - now the Electronics Industries Association).  In 1935, RCA had demonstrated a fully electronic 343 line television system.  This event raised the ambitions of many in the radio industry to open a new market, and a spirited industrial contest was thereby joined.
    The FCC presided over the arena and its then Chief Engineer, Commander T.A.M. Craven, set forth the ground rules: frequency allocations had to be agreed upon, and standards written which would insure a high quality service, one permitting every receiver in the hands of the public to derive pictures from every transmitter licensed by the Commission.  Thereupon, in 1936, the RMA Television Allocations Committee, one of the two RMA groups, made the most basic proposal of them all: that the channel should be 6-MHz wide. This was a very wide channel indeed for its time, and it was chosen with the explicit understanding that double sideband amplitude modulation would be used for picture transmission, permitting no more than 2.5 MHz of video bandwidth.

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    The other group, the RMA Television   Standards Committee, also in 1936, then proposed system standards suitable for the 6-MHz channel.  Recommended were 441-line scanning, 30 frames per second interlaced 2 to 1, double-sideband negative modulation for the picture signal, an aspect ratio of 4 by 3, and frequency modulation for the sound signal.  All this occurred only 11 years after tile first demonstration of halftone modulation in motion by Jenkins and by Baird, using Nipkow disk mechanical scanning.  In 1938, the RMA Television Standards Committee added proposals for the transmission of brightness, horizontal polarization, detailed specifications of the synchronizing,, signals (including equalizing pulses), and most important, vestigial sideband transmission which thereby increased the available video bandwidth from 2.5 to 4.2 MHz.
    The great enhancement of the video band should, of course, have been accompanied by an appropriate increase in the number of lines.  But this was not done.  It can hardly have been an oversight.  More likely, the 441-line picture remained because it was a plank in the bandwagon on which so many industrial giants were about to climb.  In any event, the error was corrected by the NTSC at its last meeting, March 8, 1941, when the 525-line figure was adopted, after long argument among representatives of RCA, Philco, and DuMont.
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    Formation of the First NTSC

    Aside from the cited important correction of the previous work, the first NTSC made no significant changes in the recommendations of the RMA Committees, and it was able to complete its work in nine months.  Why then was the NTSC necessary?  Did it serve a purpose?  The second question is easily answered.
    The review of prior work by the NTSC was conducted thoroughly and across the board, by competent and devoted engineers having conflicting Opinions and company positions.  So, when the standards were approved by this diverse group, they were on immeasurably sounder ground than were the RMA standards.
     
      "Casual observers of technical progress often assume that the basic forces at work are merely those of new science and improved technology. But seasoned veterans of the technical wars know that other forces are at work."  

    The other question--Why an NTSC?--requires a more complex, but largely nontechnical answer. What happened - as has so often been the case in the history of applied technology - was a conflict between powerful men bent on capturing for themselves and their companies the lion's share of a new and potentially massive industry: television broadcasting and receiver manufacture.

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    The story begins with the FCC which, in December 1939, announced its intention to authorize limited commercialization of television broadcasting.  At the same time it noted that standards had not been set and warned against any attempt to set standards arbitrarily by the authorized broadcasts.  RCA had previously, in April 1939, inaugurated service for the public in New York using the RMA standards, and limited production of receivers had been started by RCA in January of that year.  Early in 1940, RCA announced plans to step up production of receivers, to lower prices, and to augment its broadcast schedule.
    Faced with this evidence of fast-paced action by their principal competitor, others in the industry went to the FCC.  In a hearing held in January 1940, they complained that RCA's activity was in fact "freezing" the standards without industry agreement.  They also raised technical objections to some of the RMA standards.  The FCC agreed with the objectors, and in March 1940, announced that the permission to broadcast commercially was rescinded, that standards would not be set until "the engineering opinion of the industry is prepared to approve any one of the competing systems of broadcasting as the standard system," and that no commercial operation would be authorized until such agreement was, reached.  This was the clarion call for the formation ot' the first NTSC.  Until this group could resolve differences and agree with near unanimity on a set of standards, commercial television was stopped dead in its tracks.
    The impasse was cleared by the NTSC.  It began in a meeting between Dr. Walter R. G. Baker and James Lawrence Fly, Chair-man of the FCC, in 1940.  At this meeting, at the urging of Chairman Fly, Baker agreed to set up the NTSC.  Baker, a General Electric Vice-President who was also RMA's Director of Engineering, was well aware of the depth of the industry conflict that had to be resolved and he went about the job in masterful fashion.  All organizations, whether members of RMA or not, were invited to name representatives to the NTSC, the only requirement being technical competence to deal with the issues involved.  Complete minutes would record the stands taken by all members of the NTSC and its panels.

    The industry responded promptly and well.  Indeed, it had no choice, if the television industry was to resume its growth.  In all, the first NTSC had 168 committee and panel members, it devoted 4,000 man-hours to meetings and left a record of 60,000 words.  By the time it finished its work, in March 1941, it had reviewed and endorsed the NTSC standards.  They are still in use today in the United States, Canada, Mexico, Japan and some ten other countries.  The only present change is their narrower tolerances on the scanning rates to accommodate color television.  The net effect on the industry was, of course, that the field was opened up to all comers on a more even-handed basis.  RCA continued to maintain its preeminent position, but there is little doubt that the market was greatly extended by the presence of many powerful competitors.

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    The Color Television Wars

    Incompatible Versus
    Compatible Systems

    The first NTSC explicitly disavowed the possibility of compatible color (if indeed it ever imagined that compatibility was possible).  At the insistence of CBS representatives, NTSC proposed to the FCC that field tests of color systems be encouraged, using the NTSC monochrome standards in all respects except the number of lines and the field and frame frequencies.  This was early evidence of CBS's long, hard and costly battle, ultimately unsuccessful, to put across adoption of its incompatible field-sequential system.  As a matter of fact, the coming of color television was marked by an epic battle between , two strong personalities: David Sarnoff, Chairman of RCA-NBC, and William Paley, Chairman of CBS.  During the meetings of the first NTSC in November 1940, Peter Goldmark of CBS presented to it an impressive demonstration of field-sequential color, using 343 lines, 120 fields per second and a video channel of 6 MHz.  Later proposals to use two or three contiguous 6-MHz channels for higher definition and/or lower flicker, were dashed by the fact that, in 1948, the FCC, dismayed by the shortage of channels for the burgeoning monochrome service, had ordered a freeze on the licensing of further stations that did not end until July 1952.

    This interruption of the progress of the industry had an immediate and powerful effect on Sarnoff and Paley.  Sarnoff then decided that a wideband color service would never be authorized and that a compatible system, which would preserve the existing black-and-white service, had to be invented.  Paley, for his part, ordered an all-court press in favor of the CBS field-sequential approach.  This resulted, in 1949, in a CBS petition to the FCC for immediate authorization of a field-sequential system employing 405 lines, 144 fields per second and a 6-MHz channel.  The FCC in July had requested information on the practicability of all color systems planned for the 6-MHz channel.

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    In September 1949, at a hearing that lasted many months, the FCC received a reply to its inquiry from the JTAC (Joint Technical Advisory Committee), a joint creature of the IRE (Institute of Radio Engineers) and RMA.  JTAC's tabulation included the field-sequential CBS proposal, a line-sequential proposal by CTI, and a dot-sequential proposal by Philco.  Everyone in the industry knew that RCA also was hard at work on a dot-sequential, compatible system but (presumably under the direction of its Patent Department) RCA had not revealed its work.  Just before the JTAC made its presentation, on August 25, 1949, RCA broke its silence and the JTAC table was amended accordingly.  Thereafter RCA engineers took the stand, reported the details of their system, and recommended a complete list of standards to implement their system.
    The FCC, in its orders following that hearing, completely misread the portents.  It disqualified the line-sequential and dot-sequential systems and ruled that the CBS incompatible field-sequential system could proceed with commercial broadcasts.  After litigation brought by RCA reached the Supreme Court, and the FCC position was upheld, the CBS color broadcasts began on June 25, 1951.  In retrospect it can easily be understood why the public resolutely paid no attention whatever.  The CBS broadcasts, being incompatible in their scanning standards with those of the black-and-white receivers in the hands of the public, could not be received in any fashion by the public at large.  The Korean War provided a timely opportunity for the abandonment by CBS of its color broadcasts, which ceased October 19, 1951, less than four months after they had started.
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    Second Calling of the NTSC

    Meanwhile, back in 1949, it was clear to Dr. Baker that the time had come for a second calling of the NTSC to provide industry wide agreement on a set of standards for compatible color.  This second incarnation began in January 1950.  At its last meeting, in March 1953, the NTSC approved unanimously the present compatible color standards, and Peter Goldmark of CBS seconded the motion to approve.
    Here was an example of what can happen in a free society.  Despite vigorous government opposition, the truth or falsity of counter claims could be worked out, painfully, but worked out to the satisfaction of the many contesting parties.  The new science and technology of compatible color were laid out in all their confusing glory before 315 NTSC Committee, Panel, and Subpoena members.  After 32 months (nearly four times the time taken by the first NTSC), it reached agreement, leaving behind a record of 18 mimeographed volumes totaling 4,100 pages and the better part of a million words.

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    Principles Adopted in 1953

    The dot-sequential system of RCA was the starting point for compatible color, but refinements from other sources proved essential and these were introduced after lengthy discussion and field tests.  Perhaps the most significant of these improvements was the constant luminance principle invented by Loughlin, of Hazeltine, and his proposal to bypass the luminance signal around the color-sampiing circuits.  These techniques removed the dot-interference effects that had been the principal shortcoming of dot-sequential systems.  Other work by the second NTSC included the comprehensive study of the color subcarrier modulation system, the choice of angles and modulation method, and sideband distributions for the I and Q subcarrier signals.  Extensive field tests included a confirmation of the ability of the color synchronizing burst to withstand the effects of severe noise.  Many other proposals were discussed, tested, modified, and accepted or rejected.

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    Turn of the Tide

    As can be imagined from this re-call of history, the second NTSC was not welcomed by the FCC.  One of the Commissioners, R. F. Jones, went so far as to assert that the engineers testifying in favor of a compatible system were in a conspiracy against the public interest.  In fact, the FCC pointedly ignored the NTSC for two years after it began work, at the end of which time FCC engineers were permitted by the Commissioners to attend NTSC meetings and demonstrations.  By that time, 1952, the general embarrassment in Washington over the earlier incompatible color fiasco had subsided.  By 1953, industry wide agreement had been obtained on the NTSC standards, and the FCC authorized their use effective December 23, 1953.

    Thereafter Mr. Paley had to follow in General Sarnoff's footsteps, but this disadvantage was tempered by the ensuing history.  It was not until ten years later, in 1964, that the public finally took the bait and began to buy color receivers in substantial numbers.  During that decade, Mr. Paley had time to catch up, while General Sarnoff presided over a total investment by RCA in excess of $100 million before the tide turned.  Sarnoff's faith and perseverance, without which color television service would have been longer delayed, were recognized at a banquet commemorating his 70th birthday, at which the CBS President served as toastmaster.

    "It can fairly be claimed that the second NTSC was the most effective operation in the history of technical standardization.  The standards it set up have been adopted by the rest of the world in nearly all major respects."
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    The Impact of NTSC on the World

    Difference between NTSC, PAL, and SECAM

    It can fairly be claimed that the second NTSC was the most effective operation in the history of technical standardization.  The standards it set up have been adopted by the rest of the world in nearly all major respects.  The most widely used system of color television, PAL, employs a chrominance subcarrier, frequency interleaving of luminance and chrominance components, the constant luminance principle - all taken from the NTSC scheme.  The major differences are that, in PAL, the phase of the color components is reversed from line to line, with corresponding reversal at the receiver, and that simple color-difference signals are used in place of the NTSC I and Q signals.  The effect is to achieve more accurate color values in the presence of multipath and some other types of interference and to reduce quadrature crosstalk.  The SECAM system (considered by most engineers not practicing in France, Russia or their dependencies to be inferior in design to the PAL system) requires the receiver to memorize the content of each line, successive line signals being transmitted in the two color components.  The color signals are sent on a chrominance subcarrier by frequency modulation, thus precluding the use of frequency interleaving.  Both PAL and SECAM require somewhat more complex receivers and have somewhat lower vertical color resolution, but highly satisfactory reception is achieved by each system.

    By all odds, the major difference in performance among NTSC, PAL, and SECAM is the superior horizontal resolution of the latter systems.  This arises from two causes: more fundamentally from the wider channels (7 and 8 MHz) used, with correspondingly wider video bandwidths (variously set at 5.5, 6, and 6.5 MHz); less fundamentally from the lower frame rate (25 frames per second) which in turn has the deleterious effect of increasing their susceptibility to flicker problems.  These comparisons prompt a strictly personal view of the ways in which the NTSC standards could be improved, if we had it to do over again.

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    Some Possible Improvements
    of the NTSC Standards

    Clearly, we would have been better advised to choose a wide channel width, say 8 MHz.  This choice would have cut station allocations in the ratio of 8 to 6, but on balance the improvement in the service would have been, in the author's opinion, well worth it.  The NTSC field rate of 60 fields per second is clearly the right choice, agreed upon throughout the world as the proper base for future high definition standards.  With an 8-MHz channel, the 525-line image could have been properly chosen at a considerably higher value, say in the vicinity of 700 lines.  Finally, the NTSC I and Q components which have served us so well are now considered to, have no particular advantage over the simple color-difference signals of PAL, and have some disadvantages indicated by experience with the PAL system.

    Despite these minor faults showing that the NTSC system (which preceded the others by ten years) is not perfect in all respects, it remains a system having far more potential than we currently extract from it.  Troubles with cross-color effects in the overlap regions between the luminance and chrominance spectra, have forced designers to limit the luminance bandwidth of receivers produced to date to less than 3 MHz.  This results in a loss in luminance resolution compared to that permitted by the 4.2 MHz offered in the NTSC standards.
    Only recently has the announcement been made that comb filters are available in some top-of-the-line receivers, with substantial increase in luminance resolution.  Also, the earlier introduction of the vertical interval reference (VIR) system, which constrains the receiver settings of chroma and luminance to follow the values set at the studio, is now increasingly popular.  So it is that many of the problems of the NTSC standards are being solved by new technology.

    Fortunately, also, the problem of program exchange between originations on different standards has been solved by the digital video frame store, at a cost that only large networks can afford.  It is very effective indeed.

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    Outlook on the Future

    The frame store is, in fact, the occasion for asking whether, in the not too distant future, the call may arise for a third NTSC, hopefully under international auspices.  If and when frame stores are so reduced in complexity and cost that they can be incorporated in receivers, then narrow band transmission of television may be in prospect, among several other attractive possibilities.  The eye, as we well know, cannot consciously respond to information clues at any rate faster than about 50 bits per second.  A whole audience, reacting in different ways to different aspects of the presentation, probably could be satisfied with a rate of information clues not greater than a few thousand bits per second.  To achieve such low rates of information transfer in television, we must eliminate the redundancy in scanning by concentrating only on the changes between frames.  Total scene changes will, in this case, require time for full-store accumulation, much indeed as does natural vision.  To adopt this approach requires the digital storage of whole frames and adroit changes in the storage to follow the significant information clues and ignore all else.
    This possibility has been understood in its essentials throughout the history of television engineering, and it is still far from practical reality.  But when we consider how much digital processing and storage can now be bought in a hand calculator priced at $7.50, we need, perhaps, not be too discouraged about future possibilities.

    If the experience of the two NTSCs is any guide--and I believe it is--we need not only to practice new science and economical reductions.  We must also deal with the human factors of ambition, foresight, strong drives for profit and power, and knowledgeable coordination by government and within the industry.  That such human factors are at work in the world today, pushing for a new day in television, no one among the readers should ever doubt.  The only question is from whence and when will the great push come.

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