Video History -- In Support of Composite Video
What we now know as NTSC (U.S. National Television Standards Committee) composite video is a variation of the encoding of the color TV video signal developed by RCA and others and adopted in early 1953. At the time there were two other competing systems.
The CBS system transmitted entire fields for each color, as, first video frame odd scan lines for red, first frame even lines for green, next field of odd lines for blue, next field of even lines for red, and so on. A wheel with colored windows spun in front of a black and white picture tube to give each video field the correct color.
One other system had individual scan lines representing red, green, and blue respectively. It, like the RCA system, required the shadow mask picture tube we know today.
The RCA system (actually several versions developed between 1949 and 1953) was the only one of the three that was forward and backward compatible. Existing black-and-white TV sets could receive the color programs (in black-and-white) and also color TV sets could receive black-and-white programs (in black-and-white). Today (2009) black-and-white TV monitors (with no channel selector or tuner) are still being made. I would have thought that the other two systems would be compatible if they used the same scan rate (525 scan lines, approx. 480 of them active, interlaced scanning) but no mention of the scan rates is made here.
The following is the entire text reproduced from the document, Answers to Questions About Color Television, published by Radio Corporation of America, 30 Rockefeller Plaza, New York, 20, NY on March 30, 1950. It contains RCA's arguments for the Federal Communications Commission (FCC )to choose its system over the other two. At that time, some RCA color broadcasting was already in progress, quietly proving its compatibility with the then usual black-and-white broadcasts, mostly in the Washington DC area.
I have added notes here and there in square brackets.
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ANSWERS TO QUESTIONS ABOUT COLOR TELEVISION
RADIO CORPORATION OF AMERICA
March 30, 1950
Color television is ready for the adoption of basic technical standards, which would permit its early development as an outstanding new service to the American public.
On this point, there is no disagreement among the rival advocates of three different systems of color television. Each proponent has informed the Federal Communications Commission, which will determine the matter, that he is prepared to discuss the setting of standards for his respective system. Each system, however, would require a different set of standards.
The primary question is, then, what kind of standards are to be adopted?
The Radio Corporation of America believes that the all electronic, high-definition, completely compatible system of color television, as developed by RCA Laboratories, offers the greatest benefits to both the industry and the public. The system has been described in detail in 16 technical bulletins and statements* filed by RCA with the Federal Communications Commission and distributed by RCA throughout the radio-television industry.
[ Back then, high definition meant a resolution equal to the resolution seen on the average black-and-white TV set, which resolution, horizontally, was around 240 alternating dark and light dots within a distance equal to the picture height, or 75% of what could be broadcast and displayed with superb equipment. ]
The purpose of this report is to summarize in non-technical language the clear-cut advantages of the RCA system and relate them to the practical problem of providing a regular service of color television to the public.
C. B. Jolliffe
Executive Vice President in Charge
RCA Laboratories Division
* Listed in Appendix 2
ANSWERS TO QUESTIONS ABOUT COLOR TELEVISION
The basic problem in color television, as envisaged by research scientists of RCA Laboratories, has been to develop a system that is unlimited - technically or otherwise - in its possibilities for future growth and expansion; also, one that is completely compatible with the present method of black-and-white television. This, RCA has done.
In achieving its goal, RCA has created an all-electronic, high definition system of color television of unmatched quality and practicality. All fundamental problems relating to the system have been solved, and its refinement and simplification are progressing rapidly. The correctness of its technical concept has been proved in hundreds of hours of experimental operations. Its introduction would come as a natural and logical addition to present services of black-and-white television.
The overall characteristics of the RCA color system, which no other method demonstrated so far can fully equal, are:
1. Complete compatibility with present black and white television system (color telecasts are reproduced in black-and-white on receivers now in use without any modification),
2. High-definition pictures,
3. Unlimited picture size,
4. Bright, flickerless pictures,
5. High color stability and fidelity,
6. Freedom from color break-up and fringing, and
7. All-electronic (no mechanical moving parts).
Judged by purely scientific and engineering criteria, each one of these characteristics is fundamental and important. Put together, they constitute a color television system that is efficient and practical in every regard - technical, aesthetic, and economical.
DIFFERENCES IN THREE SYSTEMS
The basic differences in the three systems now before the FCC lie in the method each employs in picking up and reproducing televised images in color. The RCA system is known as the "dot-sequential" field-simultaneous method. The other two are described as "field-sequential" and "line-sequential".
[This is our present understanding of RCA's 1950 dot sequential system. From the red, green, and blue component signals from the camera, the video waveform was constructed using a few microseconds of the R signal, the next few microseconds of the G signal, then of the blue signal, then of the red signal, etc. alternated. Fine detail (high frequency) content from all three signals was combined and superimposed on the final video signal. On a black and white TV set, this signal would still produce a high quality picture. An approximately 3.58 MHz signal, locally generated in the TV set, was used to provide a rhythmic cadence to alternately turn on the red, green, and blue electron guns in the picture tube(s). Only one gun was on at any given time. The visual result actually had each scan line broken up into segments about 0.5% of the screen width each (corresponding to approx. 2 MHz time multiplexed sharp sampling), pixels if you wish, alternately painted by just the red beam, just the green beam, or just the blue beam. We believe that horizontal interlace meant that the red spots were not all in the same vertical line, the green spots all in the same vertical line, etc. and also that a given spot might be red for one video frame, green for the next frame, and so on. The spots were not pixels in the sense that intensity could vary within a colored spot to give added luminance resolution. Other colors were obtained by groups of juxtaposed red, green, and blue spots which is the same process now referred to as dithering. "Dot simultaneous" was probably the term used to describe the present day NTSC video signal when any or all of the electron beams could be on for any or all parts of each scan line. This allowed different colors to be made using mixing as opposed to dithering.]
The field-sequential type of color television is not compatible with the present system of black-and-white television. It is subject to flicker, color break-up and color fringing. As demonstrated, it is limited in picture definition and it utilizes a motor driven, mechanical color disk in the receiver as well as in the camera.
[ Some of today's DLP projectors use a field sequential system with one image generating panel together with a color wheel to save the cost of having separate (more expensive) image generating panels for each of the colors red, green, and blue. Everything is scanned much faster than the original NTSC, up to 180 non-interlaced frames alternating red, green, and blue. The original CBS assigned alternating colors red, green, and blue to the interlaced fields in turn for a total of 48 red fields, 48 green fields, 48 blue fields, 144 fields in all per second. (In order to fit the 6 MHz channel width, the number of scan lines per frame was reduced to 405 and the horizontal resolution was reduced also, making the system incompatible with existing broadcasts, and still left a lot of color flicker.) Today, some viewers notice color fringing of pictures from some models of single panel DLP projectors.]
The line-sequential system is all-electronic. As described and demonstrated, it is limited in picture definition and brightness, and is subject to line crawl or flicker.
None of these limitations is to be found in the RCA system.
As to the relative technical status of the three systems, the RCA dot-sequential method is in an advanced stage of development and will be ready in the immediate future for commercial design. The line-sequential system is in the early experimental stage.
The proponent of the field-sequential system (CBS) previously claimed that its system was fully developed and required no further field testing. Recently, however, it declared that it welcomed RCA's development of the single tri-color picture tube and said that that tube could be used effectively in its system. It also claimed that by adopting the principles of "sampling" and "horizontal interlace" (which RCA developed for its system) it could achieve higher picture resolution which heretofore it has been unable to accomplish.
TECHNICAL ADVANCES OF RCA SYSTEM
Outstanding progress has been made in the technical development of the RCA system since it was first publicly demonstrated on October 10, 1949. Color stability has been achieved and color fidelity has been brought to a high level. Circuits have been simplified, and the number of tubes and the size of cabinets have been substantially reduced.
One of the most important advances is RCA's development of single direct-view tri-color picture tubes for television reception. These tubes will have a significant bearing on the ultimate design and cost of color television receivers.
Research on color television in RCA Laboratories started many years ago. An unequalled store of knowledge and experience in the subject has been accumulated. The present high state of development of the RCA color television system is the product of this work.
1. THE RCA SYSTEM AND COMPATIBILITY
A compatible color television system is one that can be superimposed on the present system of black-and-white television without causing any disruption of telecasting service or degradation of the picture quality. It has the obvious merit of representing no loss of programs to owners of present sets and no loss of audiences to telecasters.
Compatibility means that color telecasts could be reproduced in black-and-white on monochrome sets now in use without any modification. On the other hand, a non-compatible system, such as the field-sequential method, would mean that color telecasts could not be reproduced in black-and-white by present receivers unless their owners went to the expense of having them adapted.
The economic aspects of compatibility are of great importance to the future expansion of color television. If a non-compatible system were adopted, it is questionable how many of the present telecasters could carry the financial burden of losing their regular audiences for black-and-white television while telecasting in color. Even assuming that the present owners of television sets would be willing to have them adapted, this job would require the services of hundreds of technicians working thousands of hours in any one major city alone. To do the job in all television communities, it would cost the public many millions of dollars.
The telecaster, operating under a compatible system, is in a position to transmit his popular programs in color without any loss of his present audience. The public is thus encouraged to purchase color sets. Under this plan, receiver sales would increase and audiences would grow.
The complete compatibility of the RCA system has been effectively demonstrated in hundreds of hours of experimental color telecasts. In Washington, D. C., where the experiments have been held, the color telecasts built up an audience among the owners of black-and-white receivers*.
(*See page 18. Statement before Federal Communications Commission, March 22, 1950, by Joseph H. McConnell, President of the National Broadcasting Company (a service of RCA) setting forth the plans of NBC [then owned by RCA] for telecasting programs in color.)
2. HIGH-DEFINITION PICTURES
One of the most important characteristics of the RCA color system is high-definition pictures. It has the same 525 line standard for definition as the present black-and-white television, and the detail of pictures is sharp and clear. Using the same comparison, the field-sequential method, as demonstrated, has 45 per cent less detail horizontally and 20 per cent less vertically. The definition of the line-sequential system is substantially lower vertically.
[ By increasing the frame rate, the amount of color fringing would be reduced, but to fit in the channel bandwidth provided, the video signal would then have to have greatly reduced horizontal resolution and/or fewer scan lines.]
Only a color television system of high picture definition and brightness can be expected to reproduce satisfactorily the full detail and pictorial interest of people, theatrical sets, scenery, props, architecture, paintings, art objects, and other graphic material. This fundamental requirement also applies to the readability of lettering on package goods and in various types of documents, as well as to the discernability of the texture and pattern of fabrics and other materials.
It is obvious that the excellence of picture detail will have an important bearing on the public's acceptance of color television.
3. UNLIMITED PICTURE SIZE
Another of the more important characteristics of the RCA system is unlimited flexibility of picture size in color television receivers. The single tri-color tube can produce the large pictures so desirable for direct-view home receivers. For projection-type reception, it is believed that the tube can be used for home sets and for theatres.
[ As things turned out, three separate single color picture tubes have worked out better than one tri-color tube for projection TV sets. About the only current use of a tri-color tube for projection is the do-it-yourself "one hundred inch TV" advertised in the back of magazines such as Popular Science. Results for this application have usually been dim, difficult to focus pictures. ]
The public has already shown a preference for increased picture size in black-and-white television, and there is now a definite trend toward large television pictures in the home.
Picture size in mechanical-type receivers is limited by the use of a revolving color disk, which must be more than twice the diameter/size of the receiving tube. When pictures bigger than 12-1/2 inches in diameter [or diagonal] are desired, a large magnifier, as well as a mechanical disk, must be attached to the set in front of the picture tube. In fact, the proponent of the mechanical type receiver conceded at the FCC hearings that its mechanical method is impractical for anything larger than a 12-1/2 inch tube.
[For larger pictures, a wheel of the necessary size could not be manufactured economically, it would be subject to such rotational stresses that one of poor quality could disintegrate explosively.]
Both the rival field-sequential and line-sequential systems claim they can use RCA's tri-color kinescopes [picture tubes; CRTs]. Such use, however, would not alter basic limitations of these systems. For example, it would not make the field-sequential system compatible.
4. BRIGHT, FLICKERLESS PICTURES
A further advantage of the RCA color system is found in the complete absence of flicker in pictures reproduced at the receiver. In addition, picture brightness may be at whatever level the public prefers. For example, picture brightness in receivers of the RCA system can be as much as five to ten times as great as in those of the field-sequential system before threshhold flicker is reached.
Picture flicker, requiring low-level brightness, is characteristic of the field-sequential system. Flicker and brightness are related to the extent that an increase in brightness means a corresponding increase in flicker.
[This flicker is a psychological effect accentuated by the alternating red, green, and blue colors of the successive fields. ]
From the practical point of view, picture brightness ranks in importance with definition, size, and color stability in the achievement of realism in color television reception.
5. HIGH COLOR STABILITY AND FIDELITY
Automatic color phasing in the RCA system, by electronic means, assures complete color stability.
[ Automatic color phasing is accomplished by including a few cycles of the approx. 3.58 Mhz color subcarrier in the horizontal retrace interval, the time when the electron beam is returned to the left of the screen for the next scan line. So long as the subcarrier frequency generated in the TV set did not drift from that used to modulate the broadcast by more than a third of a cycle (about 100 nanoseconds) during the drawing of any one scan line (about 63.5 milliseconds) the TV's circuits would usually lock back in sync. with the broadcasting station. Since color depends on the phase of the color signal, loss of phase sync. would cause all the colors to become incorrect.]
The primary colors used in cameras and receivers of the RCA system are green, red, and blue. The range of color that it is possible to produce at the receiver compares favorably with the best processes of color reproduction and is much superior to most commercial processes. This means that televised programs will be reproduced on home receivers with life-like naturalness.
[ The red phosphor used in the first RCA tubes delivered one of the best reds every obtained, but was discontinued since the brightness achievable was quite low. Today's red phosphors are "sort of" orange-ish. ]
6. FREEDOM FROM COLOR BREAK-UP AND FRINGING
The fundamental nature of the RCA color television system precludes any color break-up or color fringing. This is due to the fact that the three primary colors are reproduced simultaneously on the screen of the receiver. In the field-sequential system, however, mixed colors are subject to breaking into their primary elements at the receiver. Annoying to viewers, color break-up also creates serious limitations on color television programming.
[ To recap, the color fringing occurs because, after, say, the red field is displayed, the upcoming green field has moving subjects in a slightly different position, and the upcoming blue field has yet different subject positions, and so on. The slow (actually 48 of each color per second in the CBS system) refresh rate for each individual color results in annoying flicker and eyestrain.]
It would be difficult in a system affected by color break-up and fringing to present satisfactory close-up views of individual participants in high-speed sports, certain kinds of dancing, and other types of variety entertainment. This unwanted effect is pronounced when a person or object moves quickly across the color television camera's field of view at fairly close range. It could be caused by so simple an action as the waving of a white handkerchief or the pitching of a baseball.
7. ALL-ELECTRONIC (NO MECHANICAL MOVING PARTS)
An all-electronic system of color television, as developed by RCA, has obvious advantages. It is in the established trend of television technology, and would permit the ready utilization of all the most modern techniques in radio communications and electronics. Moreover, such a system can make full use of electronic improvements as they become available.
Color television systems employing electrical motors and mechanical color disks offer little likelihood of important technical progress. They represent a step backward in relation to all-electronic radio receivers and black-and-white television. Such a mechanical color television system would move back toward the methods first experimented with and long since discarded in the color motion-picture field. In fact, the mechanical disk for television scanning, invented in 1884, was abandoned in favor of the all-electronic method just as soon as the iconoscope was developed.
The all-electronic system, therefore, belongs to tomorrow as well as to today.
SINGLE DIRECT-VIEW TRI-COLOR PICTURE TUBES
Critics of the RCA color system have said: (1) it is too complex and costly, and (2) it cannot be transmitted over coaxial cables.
A complete answer to the first point, which, at the same time, shows flexibility of the system, is RCA's development of single direct-view tri-color picture tubes (kinescopes). This type of tube represents the ultimate in color television reception, and is a major technical development in its own right.
The single tri-color tube eliminates the necessity of using the three-kinescope arrangement seen in RCA's early experimental receiver models. With tri-color tubes, receivers can be of either the popular direct-view kind or the home projection type. In either case, design of receivers would be relatively simple and would involve no special problems for manufacturers. In outward appearance, color receivers would be quite similar to those used in black-and-white television, unencumbered by mechanical parts or large revolving color disks.
Several types of the tri-color tube are under experimental development in RCA Laboratories, and two of them have reached a fairly advanced stage. These two types show an attractive picture with good resolution and good color. That the tri-color tube represents the most efficient and practical means of reproducing television in full color, is definitely assured.
The tri-color kinescope is extremely advantageous as an element of the RCA color system. It will increase picture size and brightness. It will minimize color registration problems and, in some forms of color kinescope, it will wholly eliminate any registration problem in the receiver. It will reduce cabinet size. It will simplify circuits and construction. It will permit economies in manufacture and service. And it will do all this without requiring any change whatsoever in the fundamental RCA color system or in its superior performance.
Proponents of both mechanical field-sequential and line-sequential color television have welcomed RCA's development of the single tri-color picture tube with the claim that it can be used effectively in their systems.
The fact is, however, that even with the single tri-color tube the field-sequential system still would lack compatibility with black-and-white television. It would still have other defects inherent in the field-sequential system.
In the line-sequential system, the picture quality of the tube would be determined by the inherent limitations of the system and would show poor vertical detail.
Costs of receivers equipped with the single tri-color tube would be about the same for all three rival systems.
COLOR TRANSMISSION OVER COAXIAL CABLES
Radio relays are eminently satisfactory for transmitting the RCA color system, but, as presently equipped, coaxial cables will not carry the color signals. Such signals, when transmitted by coaxial cable, are reproduced as black-and-white pictures. At least three-fourths of the nation's intercity television network will ultimately be radio relay. By early Fall, these facilities will link such important cities as Boston, New York, Philadelphia, Wilmington, Baltimore, Washington, Pittsburgh, Cleveland, Toledo, Detroit, Chicago, Milwaukee, Des Moines, and Omaha. As to coaxial cables, color television transmission requires the addition of equipment to cables presently in use so that they will pass a wider band of signals.
In its annual report to stockholders for 1949, the American Telephone and Telegraph Company stated:
"We are also keeping in close touch with color television developments and will be in a position to transmit color Programs when that is desired."
[ Most coaxial cables then had a bandwidth under 3.5 Mhz which resulted in loss of the color subcarrier and most of the color signal content. Also the horizontal resolution of monochrome video signals would be restricted to about 240 lines, which actually was the resolution of the average TV set (due to manufacturing skimping) then and is approximately that of VHS tape. ]
RCA SYSTEM IN MODERN TREND OF DEVELOPMENT
As one of the latest advances in electronics, the RCA color television system is representative of the modern trend of development. It utilizes all relevant progress in radio communications, broadcasting, radar, and electronics.
As described in the engineering terms of the numerous technical bulletins distributed to the industry, the RCA system takes advantage of such outstanding advances as sampling, time-multiplex transmission, "mixed highs", and dot interlacing. By their use, the RCA system compresses within the transmitting band width now specified by the Federal Communications Commission for black-and-white television all of the necessary picture and control information for a full high-detail color picture. The RCA system provides the best service in a 6-megacycle [...per second, or 6 MHz,] channel.
RCA believes that, in the selection of standards for any color television system, there are certain correct general guiding principles.
From the viewpoint of the public, the system should enable reasonable costs, high-definition pictures unlimited in brightness and size and free of color faults. Receivers should also be attractive in appearance, simple in operation, and should have a satisfactory operating life.
From the viewpoint of the telecaster, as well as of the public,, the system should have complete compatibility with black-and-white television. The telecaster should not be required to take serious audience-losses in switching from black-and-white to color programs.
From the viewpoint of the manufacturer, the system should provide reasonable engineering development and design possibilities and normal use of available television manufacturing methods and components. In addition, there should be the possibility of attractiveness and excellent performance in the manufactured product, reasonable costs, ease of shipment, installation, and servicing.
The RCA all-electronic color television system alone meets all of these conditions and requirements. It is ready for the adoption of basic technical standards and, when such standards are set, RCA is prepared to carry out the necessary product development that will lead to commercialization of color television.
STATEMENT ON PLANS OF NBC FOR BROADCASTING PROGRAMS IN COLOR
by JOSEPH H. MCCONNELL,
President, National Broadcasting Company
Testifying before FCC on March 22, 1950
I am appearing here to state what NBC would do in broadcasting color television programs, both local and network, if the Commission authorizes the RCA color system for commercial service.
Immediately upon Commission authorization we would extend our Washington color programs to at least 12 hours a week. The programs would include commercial as well as sustaining shows, in choice time as well as at other hours.
We are already broadcasting 8 hours a week of color programs in Washington for the purpose of testing the RCA system. The programs used are part of WNBW's regular operating schedule. Regularly scheduled color broadcasts were started in Washington on January 9, with a daily hour long afternoon program, Mondays through Fridays. On March 13 we extended this color schedule to include the regular 6:30-7 PM, WNBW broadcasts, Mondays through Fridays, and an additional quarter hour later each day on Mondays and Tuesdays. In addition to giving us technical experience, our work with color in Washington has given us valuable training in production techniques for color programs. This includes, for example, experience in costuming, make-up, the design of scenery and lighting.
Upon Commission authorization of the RCA system, color programs originating in Washington would be sent to New York for broadcast in color there. Existing relay facilities as well as AT&T relays, which the Telephone Company has said will be available this summer, would be used for this purpose. This means that there would immediately be color broadcasting by us in the New York area.
In addition, we would commence at once to equip our New York station for originating color programs there. When adequate facilities are completed in New York, our station WNBT would broadcast at least 12 hours a week of color programs. Within a year thereafter we would expand that schedule to at least 18 hours a week.
Since the RCA color system presents no problem of reception on present sets, our color programs would be selected from our regular schedule. They would include programs in choice viewing time and feature some of our most popular sustaining and commercial programs.
The programs would consist of both local and network shows. Our stations in Chicago and Cleveland would receive color programs over the AT&T radio relay, which the Telephone Company has said will be available this summer. Thus these stations would be able to transmit in color before they have their own facilities for originating color broadcasts.
All our network programs in color would of course be available for color broadcasts by stations reached by radio relay. By the end of summer we understand that radio relay facilities will extend from Boston to Omaha serving such intermediate points as Providence, New York, Philadelphia, Pittsburgh, Cleveland, Toledo, Chicago, and Davenport-Rock Island. Other points served by radio relay at that time will include Wilmington, Baltimore, Washington, Detroit and Milwaukee. If the General Electric relay link to Schenectady were restored, Albany, Schenectady, Utica and Syracuse would also be served in color. We would also relay color programs to our experimental UHF television broadcast station in Bridgeport, Connecticut. Regular color broadcasts from that station would give valuable information with respect to color in the ultra high frequencies.
The availability of the radio relay facilities to which I have referred means that the owners of color receivers in all these cities could receive color broadcasts. Of course, all black and white sets served by any transmitter, no matter how interconnected, can receive these color transmissions as black-and-white programs. This is the importance of a compatible system.
In fact, should the Commission authorize only a non-compatible color system, we would not be able to embark on any comparable color program.
During the time the broadcaster put on non-compatible color programs he would lose his entire circulation, except to those persons who had bought adapters, converters or new color receivers. The effect of this on the broadcaster's revenue is obvious. With a non-compatible system, he could not afford choice time for color programs unless he were willing either to sacrifice his large black-and-white audience or this Commission would authorize him to use two frequencies, one for color and the other for black and white. I do not believe that most station owners could afford the former or that it is realistic to consider the latter. I feel that, as a result, most color programs, under a non-compatible system, would be broadcast in fringe time.
[ The current mechanism for introduction of the non-compatible ATSC digital TV and HDTV has seen the allocation of a second channel (frequency) to each TV broadcast station. Stations may simulcast the same shows on both channels although as of 2001 fewer than half of all U.S. TV stations have done anything with their HDTV channel. ]
In addition, the selection of color programs under a noncompatible system would be considerably limited. The small audience would necessarily discourage the broadcaster - as well as the sponsor - from broadcasting his choice programs in color. This lack of select programs in choice time would discourage the public from converting their present black and white receivers for color and from buying new color receivers.
Telecasters have suffered considerable losses because of the relatively small number of receivers in the hands of the public during the early years. Although this situation has begun to correct itself in black-and-white television because of the tremendous public acceptance of the new medium, the adoption of a non-compatible color system would extend the period of station losses. It has taken four years of these losses to build up the black-and-white television audience to the size it is today. It would take a long time to build up as great an audience for a non-compatible color system.
In my opinion, the adoption by the Commission of a noncompatible color system would be a major factor in delaying the coming of a sound color service on a national basis. I am strongly in favor of such a service. But I do not believe it will be possible for many broadcasters to furnish such a service for a long time if a non-compatible system should be adopted by the Commission.
With more than five million black-and-white receivers in the hands of the public, the transition period to the time when an equivalent number of receivers capable of receiving color broadcasts are in the hands of the public would in my opinion be a long one.
On the other hand, with the RCA system, color broadcasts of outstanding programs in choice viewing time can become an immediate reality without any loss of present service to the broadcaster or to the public. I believe that if the Commission should standardize on this system, it would provide the greatest force to stimulate the growth of color television.
To summarize our plans if the RCA color system is authorized by the Commission:
We will immediately expand our present regular schedule of color programs in Washington.
We will immediately relay programs to New York for broadcasting in color there.
We will originate programs in color in New York as soon as studio equipment can be installed.
We will broadcast color programs from our regular schedule, including some of our most popular sustaining and commercial shows. These broadcasts will be in choice viewing time.
We will offer color programs as a network service.
[end as quoted]
CBS ADOPTING ESSENTIAL ELEMENTS OF RCA COLOR TELEVISION SYSTEM
Step by step, the Columbia Broadcasting System is adopting essential elements of RCA's all-electronic, high-definition color television system.
In doing this, CBS apparently is trying to offset the inherent limitations of its field-sequential color system. As RCA has continued to develop and demonstrate the advantages of its system, CBS's recognition of these advantages has become increasingly evident.
But, oddly enough, they still call their altered method "the CBS system".
Here is what has happened so far:
CBS AND RCA's IMAGE ORTHICON CAMERA TUBE
In the early years of CBS's experimental work with mechanical field-sequential color television, their camera pick-ups were limited to brilliantly lighted still subjects. Live action and outdoor scenes were beyond the system's capabilities.
The RCA-developed highly-sensitive image orthicon television camera tube became commercially available for the first time in 1946. Soon thereafter, CBS adapted the RCA image orthicon for its color television camera and could then, for the first time, make live studio and outdoor pickups.
Thus, the trend started.
THE RCA SINGLE TRI-COLOR PICTURE TUBE
CBS has persistently urged the Federal Communications Commission to adopt standards for color television based on its fieldsequential system, including a mechanical color disk for home receivers.
In support of the mechanical disk, Dr. Peter Goldmark of CBS told the FCC on March 1, 1950:
"Color disc seemed then and still is today the only means we know of whereby we can get optimum color rendition and color rendition under the best controlled conditions because the color filters which are put on the color disc in conjunction with a white phosphor of the cathode ray tube will give you results which are entirely predictable and entirely check with the color reproduction theory."
But the day before, on February 28, 1950, Adrian Murphy of CBS, commenting on RCA's development of single direct-view tri-color picture tubes, testified before the FCC:
"Therefore, if anybody feels we don't have a large enough picture, the RCA set will answer that for us. If anybody is concerned about the so-called all-electronic system and feels that the CBS system is eternally mechanic, the RCA tube will solve that for us. If there is some concern about the limited viewing angle that may exist because of the CBS receivers, the RCA tube will solve that. If there is any concern about lenses that we may use, the RCA tube solves that. So we really look forward to it with a great deal of anxiety."
Mr. Murphy, under prodding of a CBS lawyer, amended this statement a few mintes later by changing the word "anxiety" to "anticipation".
With those words, CBS welcomed another essential development by RCA as solving many of their problems. It does not solve, however, the inherent limitations in the CBS system of non-compatibility, flicker, low-level brightness, color break-up and color fringing.
RCA's "SAMPLING" AND "HORIZONTAL INTERLACING"
Before seeing the first demonstration of the RCA color television system, Dr. Goldmark [of CBS] testifying before the FCC, stated on October 5, 1949:
"I believe that enough is known about the CBS system - as to its strength and weaknesses - so that no useful purpose would be served by attempting further to field test the system itself."
After seeing the RCA system demonstrated, Dr. Goldmark, again testifying before the FCC said on October 11, 1949:
"I don't think that the RCA system should be field-tested because I don't think the field tests will improve the system fundamentally."
Asked by one of the Commissioners, "And do you advocate that they drop the system now?", Dr. Goldmark replied: "I certainly do."
Yet, on March 15, 1950, Dr. Goldmark informed the FCC that CBS was adopting the principles of picture "sampling" and "horizontal interlacing" to achieve high definition in the CBS system.
Both of these principles were developed by RCA and are fundamental elements of the RCA color system.
Moreover, when CBS applies these principles, as well as RCA's single tri-color picture tube, and changes its present mechanical system to an all-electronic system, field testing of the modified system will become essential. Its previous claim that no further field testing of its system is required, in fact, already has been abandoned.
On March 15, 1950, Counsel for the FCC asked Dr. Goldmark, then on the witness stand: "If you introduce this horizontal interlace principle at the transmitter it will in no way deteriorate present black-and-white receivers?" Dr. Goldmark replied: "No." FCC Counsel then asked: "Future black-and-white receivers can add it and get a bonus out of it, or if you choose not to add it, you get the lower definition. It is going to be a matter of option?" Dr. Goldmark replied: "That is right. The beauty of it is that we can go ahead and through the impetus for this kind of development, through use of color television, we can peacefully and thoroughly exploit this and introduce it at any time 'when it is ready and properly tested',* I and get this added improvement without hurting anybody."
During testimony on March 16, 1950, a Commissioner of the FCC asked David B. Smith, Vice President-Research and Engineering of the Philco Corporation: "Did I understand the significance of your recommendation was that we should abandon the CBS proposal and work toward a compatible system?"
Mr. Smith replied: "I believe I would, yes, sir."
Although CBS has adopted important elements of the RCA color television system, there still remains (among other points) the significant element of compatibility which exists in the RCA system and does not exist in the CBS system.
It is to be hoped that CBS will continue its trend of adopting elements of the RCA system and will take the few remaining steps involved in going to that system. They will thus be enabled not only to discard the mechanical scanning disk with its inherent limitations, but also to achieve compatibility and high-definition pictures. Such a forward step by CBS would bring to an end needless argument, clarify the pressing problems before the FCC and the industry, as well as benefit the public.
NOTE: All quotations are taken from the official transcript of sworn testimony in the Color Television Hearings before the Federal Communications Commission (Dockets 8736, 8975, 8976 and 9175).
* Subquoting supplied.
COLOR TELEVISION GLOSSARY
ALL-ELECTRONIC SYSTEM -- A system which, like present-day successful television everywhere, uses only electron tubes and circuit components to pick up and produce the color pictures.
CHANNEL WIDTH -- The frequency band which is occupied by a radio or television transmission. For monochrome television it is presently 4.25 mc. (4.25 million cycles [...per second, or 4.25 MHz]) for the visual signal, and 6 mc. for both picture and sound. For color television, the FCC has specified the same channel width.
COLOR BREAK-UP -- Flashes of bright and distracting color seen in viewing a field-sequential system, usually as a result of blinking the eyes or rapidly changing the direction of viewing by shifting the eye positions.
COLOR DISK -- A spinning circular disk having red, green, and blue sections or filters to produce the individual red, green, and blue pictures (primary-color pictures) in a field-sequential system.
COLOR FLICKER -- An unpleasant red, green, or blue flickering or fluttering appearance in a field-sequential picture occurring when the brightness, at a given field rate, rises above a minimal value.
COLOR FRINGING -- Unnatural fringes of color at the edges of field-sequential pictures of objects which are moving rapidly in the field of view across the line of sight. If the motion is rapid enough and the viewed objects are narrow, separate red, green, and blue images of the objects are seen and all true-color reproduction is lost.
COLOR PICTURE TUBE -- A direct-vision color kinescope or picture tube showing the program in full color directly on the screen of the kinescope. It may have one or three electron guns. In some forms of the color kinescope, color registration is automatic. The color kinescope is a recent major accomplishment of RCA.
COLOR REGISTRATION -- The accurate superimposing or registration of the red, green, and blue (primary-color) pictures used to form a specific complete color picture. For accurate registration, the primary-color pictures must be of the same size, the same internal proportions, and in the same viewing positions.
[ Color registration has long been a problem with CRT based rear and front projection TV sets, a few of which existed back then. While getting the picture dimensions to be the same for all three colors may have been easy, getting the geometry and proportions correct (without minute stretching for one color but not another, resulting in what we call misconvergence) has been difficult without microprocessor control. ]
COLOR SAMPLING RATE -- The number of times per second each primary color is sampled. (RCA color system: approximately 3.6 million times per second).
COLOR SAMPLING SEQUENCE -- The order in which the three primary colors are sampled. (RCA color system: green, red, blue).
COMPATIBLE COLOR-TELEVISION SYSTEM -- A color-television system in which the pictures can be received, in monochrome, on an unaltered black-and-white receiver.
DOT INTERLACE -- A scanning method used in a dot-sequential system to change the scanning area or order of the primary-color (red, green, and blue) dots in successive fields or groups of fields so as to create the smallest and most uniform color effects. Dot interlace is used in the RCA color system.
DOT-SEQUENTIAL SYSTEM -- A field-simultaneous color-television system in which the minute primary-color (red, green, and blue) dots are formed in extremely rapid succession along each scanning line (and usually interlaced in successive fields or groups of fields).
The RCA color system is a dot-sequential field-simultaneous system, and is inherently free from the defects of color flicker, break-up, and fringing found in field-sequential systems.
FIELD-SEQUENTIAL SYSTEM -- The color system in which a succession of individual red, green, and blue pictures (fields) are sent and received to form the final color pictures. (Such a system has been proposed to the FCC by CBS.)
FIELD-SIMULTANEOUS SYSTEM -- A color-television system in which a complete full-color field is presented as a unit so that the eye sees a succession of full-color images (and not a succession of primary-color (red, green, and blue) images). Such systems are inherently free from the defects of color flicker, break-up, and fringing present in field-sequential systems.
LINE-CRAWL -- A peculiar and undesirable effect found in certain so-called line-sequential field-simultaneous color-television systems whereby a "churning" or "crawling" vertical color effect is seen for each line of the picture.
[ If each spatial position takes its turn hosting a red scan line, a green scan line, and a blue scan line as fields are displayed, the viewer's eye following a subject moving vertically at certain speeds will see the picture break up into noticeable red, green, and blue horizontal stripes. This is analogous to the "visible scan lines separated by dark gaps" seen as the viewer's eye follows a subject moving vertically as reproduced by interlaced scanning; the even scan lines start fading to black as the odd scan lines are drawn and vice versa. ]
LINE INTERLACE -- In a television system, scanning one set of lines for one field and scanning another intervening set of lines for another field, or group of fields (to reduce flicker by increasing the number of fields for a given number of complete pictures or frames). It is used in both monochrome and color television.
MECHANICAL COLOR SYSTEM -- A system which, as did certain earlier and discarded television systems, uses mechanical moving parts to pick up and reproduce the color pictures.
MONOCHROME TELEVISION -- Television in a single neutral color; for example, black-and-white pictures.
MULTIPLEX OPIERATION -- The effectively simultaneous transmission and reception of several radio or television messages or signals within the same channel.
PICTURE BRIGHTNESS -- The brightness of the highlights of the picture (usually expressed in a unit called "foot-lamberts" In the RCA color system, any normal picture brightness is obtainable.
PICTURE CONTRAST -- The ratio of the highest brightness (highlight) to the lowest brightness (deepest shadow) in the picture. Adequate picture contrast is obtainable in the RCA color system.
PICTURE DETAIL -- The inherent fineness of structure of the television picture (usually expressed either as: (a) nominal number of scanning lines in the picture; (a) actual lines in the picture; (c) number of picture elements in the vertical dimension and in the horizotal dimension; or (d) total number of elements in the entire picture.)
PICTURE SIZE -- This is usually expressed either: (a) in square inches, (b) in terms of kinescope diameter, or (c) in terms of picture width and height. Picture size in the RCA color system is as free from limitations as in [then current] monochrome television.
PULSE-MULTIPLEX TELEVISION OPERATION -- A system for efficiently sending several television signals within the same (4.25 Mc.) television channel. For example, sending the primary-color (red, green, and blue) signals in color television in effect simultaneously in a dot-sequential system.
By using pulse-multiplex operation, the RCA color-television system compresses a full-detail 525-line picture into the same space (channel width) as used for present monochrome television. This channel requirement has been specified by the FCC.
[ I am not sure about the meaning of the word "pulse" here. Multiplex is a correct term to describe the modulation of one of the signals, here, the color or chrominance, on a subcarrier so it can be combined with the other signal (luminance) with some, ideally total, ability to separate the two. At the time separating the two had about the same accuracy as today's TV sets "without" comb filters. ]
PULSES -- Very brief bursts of electrical energy, used for the transmission or reception of signals.
BULLETINS AND STATEMENTS ON RCA COLOR SYSTEM ISSUED TO THE RADIO-TELEVISION INDUSTRY
1. "Comments of Radio Corporation of America", August 25, 1949.
2. "Engineering Statement Supplemental to Comments of Radio Corporation of America", September 6, 1949.
3. "A Six-Megacycle Compatible High-Definition Color Television System", September 26, 1949.
4. "A 15 by 20-inch Projection Receiver for the RCA Color Television System", October 20, 1949.
5. "Synchronization for Color Dot Interlace in the RCA Color Television System", October 31, 1949.
6. "A Two-Color Direct-View Receiver for the RCA Color Television System", November 9, 1949.
[Experiments prior to the unveiling of RCA Color TV (today's composite video) included a system with the equivalent of component video Y and Pr but no Pb. Color was limited to shades of orange and blue. Such a system probably would have lost out to CBS' system with the rotating red, green, and blue color wheel.]
7. "An Experimental UHF Television Tuner", December 12, 1949.
8. "Supplemental Data on UHF Tuner Described in Bulletin 'An Experimental UHF Television Tuner' ", January, 1950.
9. "A Three-Color Direct-View Receiver for the RCA Color Television System", January 9, 1950.
10. "An Experimental Determination of the Sideband Distribution in the RCA Color Television System", January 17, 1950.
11. "A Study of Co-Channel and Adjacent Channel Interference of Television Signals, Part I", January 17, 1950.
12. "A Study of Co-Channel-and Adjacent Channel Interference of Television Signals, Part 11", January 30, 1950.
13. "An Experimental UHF Television Converter", January 30, 1950.
14. "Recent Developments in Color Synchronization in the RCA Color Television System", February 8, 1950.
15. "Colorimetric Analysis of RCA Color Television System", February 15, 1950.
16. "A Simplified Receiver for the RCA Color Television System", February 28, 1950.
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