Historical Note JUNE 1981
Timing/Sync, Sync Recovery, Numbers
& Offset, D.C. Restoration, Gamma Correction
Physics: Eye, CIE
Encoding: Color Bars, Camera, RGB, YIQ, Color Subcarrier
TV/Graphics: ADC-DAC, Frame Buffers, Timebase Correction, VGA
& Practices: D.C. Restore, Proc Amps, DAs
Handbook, Benson Rev Ed. Mc
K. Jack (Brooktree's Guru) Hightext
and Video Systems, Grob, Bernard Mc
The Forces at Work
By DONALD G. FINK
|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 )
The work of the first
(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.
|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
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.
|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.
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
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
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
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.
The Color Television Wars
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.
|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.
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.
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.
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
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.
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 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.
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
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.
-- END --
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