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A digital coding technique which interfaces efficiently with composite color signals is clearly desirable for connections formed from a chain of analog and digital transmission links. This paper reviews a number of such techniques, and develops a predictive encoding algorithm, termed chrominance-corrected prediction, which is efficiently matched to the nature of the composite signal, and which avoids the need for prior separation of the signal into luminance and chrominance components. The application of composite predictions to PAL and NTSC signals is discussed, and experimental results are described which indicate that a saving in excess of 2 bits/sample can be achieved over PCM for similar picture quality.

Plateau coding is a method for efficiently coding the chromatic component of color television signals. The signal is divided into regions of approximately constant chromaticity which are transmitted by sending one set of chrominance values for the whole region. Since most changes in chrominance are accompanied by luminance changes, the luminance signal (which must be transmitted quite accurately) is used at the transmitter and receiver to indicate changes in the two chrominance signals; thus no addresses need be sent to define the boundaries of the region at the receiver. Simulations have shown that plateau coding can give pictures of high quality for chrominance bit-rates in the range 0.25-0.5 bits per luminance sample, assuming straightforward pulse-code modulation (PCM) coding of the chrominance amplitudes.

A new color-signal processing system is described which utilizes digital methods to decode the three color-difference signals from the NTSC signal. Using a 3.58 MHz crystal multivibrator as the basic time element, sampling pulses, initiated by the color burst and terminated by the following horizontal synchronizing pulse, are generated by low-level digital logic elements. These sampling pulses, delayed the appropriate time, are then used to demodulate the color-difference signals from the chrominance signal. Since the sampling pulses exist only during the active time following each color burst, no color killer is required. The system, referred to at Texas Instruments as "Color Command," uses Monolithic Integrated Circuits to generate the reference waveform and the sampling pulses, and to demodulate the chrominance signal.

Early color demodulators were described and analyzed as narrow angle sampling devices. At this time, luminance as well as chrominance was applied to the demodulators since proper operation required primary color signal outputs. With the introduction of the concept of color-difference signals in 1950, it was recognized that the color demodulator operated as a product detector and that any good product detector would make a good demodulator.

In 1965 P. Wolf of the Institute fur Rundfunktechnik, Munich, Germany, made a significant contribution to the measurement of encoded color television signals with his introduction of the 20T modulated sine-squared pulse. It possesses the ability to measure relative chrominance gain and delay, or color misregistry. This signal enjoys widespread operational use abroad. Interest in a modulated sine-squared test signal for NTSC is at present quite significant. A properly scaled test signal for NTSC is presented. The proposed signal is properly called 12.5T modulated sine-squared pulse. Compared to a 20 T, it offers: 1) an increased sensitivity to relative chroma delay, and 2) a simple scale factor for 12.5T; ?= 10d, and for 20T; ?=15.9d. Nomographs are provided for both the 20T and 12.5T modulated sine-squared pulses for NTSC. Mathematical derivation for the waveform distortion as a function of delay distortion is given in terms of the significant pulse parameter.

This paper describes a monolithic integrated circuit for processing the chrominance signal in a color television receiver. In performing the functions of color subcarrier regeneration and chroma control, emphasis has been placed on utilizing all the information available in the signal so as to approach ulti-mate system performance capability, while at the same time substantially reducing the number of external components and adjustments.

This paper presents a simple analysis of the chrominance and luminance signals required to drive the chromatron, single-gun, color television picture tube. Conversion from the NTSC signal to the required chromatron drive is explained mathematically and graphically. Two common methods of color decoding, the 1, 2, 4 and the chroma-gate systems are described and compared. Semiconductor circuits, developed for the decoder and associated signal processing, are described.

分離輝度カラーカメラでは, 分離輝度信号と色チャネルから合成された輝度信号の相違から, 原理上, 色再現誤差が生じる.また輝度・色度チャネル間に, γ, レベルなどの違いがあると, さらに大きな色再現ひずみが起こる.彩度補正はこれらを解消し, 操作性を向上する方法である.Y混合回路は, 分離輝度方式の特徴を生かしつつ, 輝度信号のSN比を改善する方法であり, 通常2-3dB改善できる.両回路とも1968年10月のメキシコオリンピックで使用され, 好結果を得た.

The paper discusses the transmission of colour television signals according to the NTSC system. The choice of the chrominance signals, their bandwidths and of the subcarrier frequency is discussed. The consequences of the method of gamma correction and of deviations from the constant-luminance principle are considered. The significance of the statistics of the chrominance signal is pointed out.

In a color television system the frequency components of the luminance and the chrominance signals consist of line spectra, the component frequencies of which are separated by harmonics of the line frequency. By being interleaved betwee. n the luminance frequencies, the chrominance frequencies share the passband near its high frequency end. The detected luminance signal in a receiver contains the color subcarrier, which produces an image with crawling dots and edges.

This paper discusses the quadrature cross talk in NTSC color television caused by the transmission of the chrominance information by a vestigial sideband system.

Transmission of color video presents a number of problems that were not encountered in monochrome transmission. The Bell System is attempting to improve transmission of chrominance information so that it is free of any phase and amplitude distortion, as well as reflections and external interfering energy.

Complete performance tests of a color TV receiver may require several man-weeks of testing time when using conventional test methods, such as those specified in Hazeltine Report 8020. A large time saving can be made by the use of two newly developed equipments to measure a number of the more important characteristics of the chrominance and luminance channels of a receiver. The purpose of the present report is to describe these two equipments, their operation, and uses.

During the past few years several monochromeimage transform-coding systems have been developed. In these systems, a quantized and coded version of a spatial unitary transform of an image is transmitted over a channel, rather than an image itself. In this paper the transform-coding concept has been applied to the coding of color images represented by three primary color planes of data. The principles of spatial transform coding are reviewed and the merits of various methods of color-image representation are discussed. A performance analysis is presented for the color-image transform-coding system. Results of a computer simulation of the coding system are also given. It is shown that, by transform coding, the chrominance content of a color image can be coded with an average of 1.0 bits per element or less without serious degradation. If luminance coding is also employed, the average rate reduces to about 2.0 bits per element or less.

The development of a multifunction integrated circuit which processes the detected video signals in a NTSC color television is described. A first generation IC has been produced which regenerates the color subcarrier using APC loop techniques. A gain controllable, chroma amplifier is also included on the chip. This IC represents the first step in a program to develop a high performance, low cost, single chip chroma processing system. Careful consideration has been given to system partitioning to maximize functional capabilities while maintaining flexibility and low cost. A detailed description of the subcarrier regenerator and chroma amplifier is given in Section II and Section III. The overall circuit organization is discussed in Section IV.

Attempts are now under way in Europe to formulate standards for color television transmission. A number of methods have been devised for the transmission of the chrominance and luminance color signals. These techniques are all characterized by signal separation, the use of difference signals, and inter-leaved frequency bands; in other words, they are all based on the National Television System Committee proposals adopted when a standardized color television system was established for the United States some years ago. Their differences lie only in the means employed for subcarrier modulation and demodulation.

It is shown that the plate output of the synchronous demodulators used in NTSC color television receivers will contain a variety of signals in addition to the desired color-difference signals. Among these are signals representing chromatic distortion due to rectification of the chrominance subcarrier, interference due to the passage of hf portions of the monochrome signal through the chrominance channel, and cross talk due to reaction between chrominance and hf monochrome signals. Estimates are made as to the seriousness of each undesired signal component, and it is concluded that there will be certain conditions under which each might produce a readily perceptible effect.

The rapidly expanding color-TV receiver market has been accompanied by much new interest in reducing receiver cost. In this report novel chrominance-signal processing circuits are described which reduce the tube count with a consequent lowering of cost, and at the same time provide desirable features such as high-performance automatic chrominance control, a color indicator, and two-mode color sync-features normally omitted in low-cost designs. Included in this report are detailed descriptions of the circuits, their modes of operation, performance data, and design data.

The devices to be described perform in two 14 pin packages the necessary chrominance and luminance functions for the PAL system prior to chrominance demodulation. One device provides the necessary chrominance processing functions, while the other device combines luminance functions with manual chrominance control. Specifically, the chrominance IC contains the functions of sub-carrier regeneration, automatic chrominance control, H/ 2 generation and identification, color killer, and burst gating. The luminance IC provides DC operation of the contrast, saturation, and brightness controls, and the functions of beam current limiting and black level clamp.

Investigation of color-television signal characteristics has led to the development of a simplified chrominance channel for television-receiver color decoders. The simple and economical circuit uses only three triodes and one switching transistor. This report contains brief descriptions of the novel features of the circuit.

Larger kinescopes and the advent of compatible color television have given increased importance to the problem of improving the transient response of television receivers. This paper is concerned with receiver design factors that make for improved electrical fidelity, although the interlocking nature of the transmitter and receiver requires some consideration of the transmitter aspects of the problem. In the receiver, the electrical fidelity is primarily determined by the delay distortion produced in the video IF amplifier, and the extent to which this distortion is compensated in the peaking circuits of the video detector and the video amplifier. Optimum results are obtained by working with both the phase-delay characteristic of the over-all receiver and the corresponding amplitude characteristic. In color receivers, prevention of delay distortion has been found to be of primary importance, as might be expected from the fact that the channel is being used to greater capacity. The factors which determine cross talk between the I and Q color-difference signals and coincidence of the luminance and chrominance information are described. Ultimately, obtaining a uniformly high standard of receiver transient response depends upon industry agreement on a standard monitor. Widespread use of a standard monitor should go far toward eliminating the present tendency for receiver designers to vary their designs to meet the peculiarities of particular transmitters.

An element differential quantizer has been used to encode three baseband components of a color Picturephone® type signal in real time. The first part of this paper is concerned with an investigation of the extra bits required to transmit chrominance information over that required for a high-quality luminance signal (coded to 4 bits per picture element). We have found that a total allocation of 1 bit per picture element to the chrominance signals leads to a high-quality color display. The second part of the paper concerns an investigation of a more efficient coding format for color sigaals. In this regard, we have determined that the color signal can be packaged into a 6.3-Mbit/s rate by allocating 12 levels for the luminance component, 6 levels for one chrominance component, and 4 levels for the other chrominance component. Only one chrominance component is transmitted each line and the missing component is obtained by line averaging. The best results were obtained by coding chrominance signals that were matrixed such that their color axes lay between the I and Q and color difference axes. A scheme is suggested for simply combining this type of coder with an analog color signal that has the chrominance information compressed into the blanking portion of the signal.

カラーテレビのノイズは画面上輝度と色度のノイズになってあらわれるが, 色度ノイズはその性質や取扱い方法が明確でない.本論文は色度ノイズの体系化を目的に, カラーテレビ系の色度ノイズを理論的に考察し試験して, 色度ノイズの表現法, さらにこれに対する等歩度色度座標を提案して, 広く一般的な色度ノイズの取扱い方について検討考察した結果について述べる.

In electronic video recording (EVR),? the color television signals are recorded on a special 8.75-mm-wide, high-resolution photographic film, with two frames side by side. One frame contains luminance information; the other, coded chrominance information. Sound is recorded on two magnetic edge stripes. An 18-cm-diameter cartridge can play 25 minutes of color programming or twice that duration of black-and-white programming. Described in this article are the processes that, starting from an original program on video tape, produce a reproduction with excellent fidelity upon playback. A detailed explanation is provided of the mechanical, optical, and electronic arrangements?including the transcoding of the chrominance signal into a conventional color television signal.

This paper presents formulas for the interpretation of the results of tests utilizing the modulated subcarrier version of the sine-squared pulse when both gain and delay inequalities are present. Exact expressions as well as suitable approximations are given, along with graphs and a nomograph to facilitate use. The region of validity of these expressions is explicitly stated.

In the NTSC signal, in order to achieve minimum interference by the chrominance signal to the luminance information, it is necessary that the subcarrier frequency have a special relationship to the field and line frequencies. This paper discusses the general conditions which are necessary as well as the practical considerations leading to a choice of the subcarrier frequency in the NTSC standards.

This report summarizes our experimental and theoretical results on the perception of displayed information. This research is concerned with four issues: (1) the effect of color on pattern recognition. (2) the measurement of statistical estimates for luminance and chrominance information in pictorial scenes, (3) the relationship between perceived changes in image sharpness resulting from changes in display modulation transfer, and (4) the development of a unified display descriptor to model the perception of both luminance and chrominance information. In this report we present the results of a series of experiments that established the relationship between our sharpness descriptor, the visual capacity, and the subjective sharpness of displayed images. The just-noticeable difference (jnd) in image sharpness was measured as a function of display bandwidth. At high spatial frequencies these measurements were found to be in excellent agreement with the assertion that display sharpness is mediated by the perceived rms gradient content of an image: a quantity proportional to the square root of the visual capacity. The addition of chrominance information to a black-and-white image was not found to appreciably affect the perception of image sharpness. Finally, the measured results on the subjective sharpness for both pictorial images and single-transition luminance edges proved to be indistinguishable. We feel that this result supports the contention that edge transitions are important in determining image sharpness in pictorial scenes.

The Bivicon is a 1½-in vidicon with two guns and targets. It can generate excellent color signals utilizing a two-frame system in which the luminance signal is projected onto one target and the chrominance information onto the other.

This paper discusses the way in which bandwidth restriction is applied in the NTSC color television specification to eliminate color "crosstalk" in the received picture. The signal which modulates the subcarrier along one axis is limited by a low-pass filter so that along this axis of the color subcarrier double-sideband conditions may be maintained in transmission and reception. The particular choice of narrow-band axis is not important if the only objective is to eliminate color crosstalk. This leaves one free to make the axes choice hinge upon some important characteristics of the human eye. These eye properties are reviewed as they apply to the NTSC signal specification.

There are a number of considerations which lead to the final choice of the chrominance subcarrier frequency in the NTSC signal. In addition to the considerations given elsewhere it is also desirable to minimize the visibility of the beats between the sound carrier and the chrominance subcarrier. This requires a slight alteration of the nominal field and line rates over those used in monochrome television.

The paper outlines the nature of a studio complex and the problems which arise from the introduction of colour television beginning with those associated with the colour separation signals. Special reference is made to the problems arising from the use of four-tube colour cameras particularly from the point of view of monitoring their outputs as well as the methods of coding to ensure accurate colour reproduction on commercial receivers. In a studio using the PAL system of colour television certain extra pulses are required for use with the coders and the generation and distribution of these pulses is discussed.The problems arising in the coding process are dealt with and in particular special consideration is given to the problems due to the colour axis switching feature of the PAL system. The effect of the axis switching on the increased precision needed in the quadrature between the two axes is also considered as well as its effect on the crosstalk problems. The design of a practical operational coder is outlined with particular reference to the problems of carrier balance and the effect of the axis switching on this parameter.The effect of colour on the mixing equipment is considered and particular reference is made to the problem of burst-stabilization during the operation of the fader controls. The subject of special effects is also discussed including the production of synthetic colour captions from black and white originals. The synchronization of the various sources at the mixer is considered in outline in so far as it affects the mixer.The design of a suitable decoder for use with colour picture monitors in a colour studio is outlined and also the general arrangements for colour picture monitoring. The requirements of a signal distribution system within a studio complex are discussed with reference to such parameters as differential gain and chrominance luminance delay.Finally, the paper considers the method of line-up necessary to ensure that coding, decoding and monitoring equipment is working correctly. In particular, a method is outlined whereby coding equipment can be completely set up using an oscilloscope to monitor the output of a coder.

Graticules superimposed on the display of modulated pulse signals can be used to define limits of gain and delay inequalities in chrominance and luminance channels. An analysis of two simple straight-line graticules, valid for small distortions, is presented.

Using a previously proposed quality-grading method, tests have been made of the effects of gain and delay inequalities between the luminance and chrominance channels of a 625-line NTSC-type broadcast colour-television system.50% favourable opinions are obtained with pictures impaired by a gain inequality, expressed as the error in chrominance-channel voltage gain, of ±56% 95% favourable opinions are obtained with a gain inequality of ±36%. For delay inequality the corresponding values are ±350 and ±210ns, respectively.

It has been observed that under some conditions N.T.S.C. colour receivers employing single-gun tubes exhibit severe cross-colour and luminance twinkle due to the presence of high video-frequency luminance information and noise. From analysis of a simple case it is established that this effect is the result of sampling of the high-frequency luminance and therefore noise components by the colour selection process (necessary to decode the subcarrier chrominance information) which takes place at the screen. Methods of eliminating or substantially reducing this objectionable effect are discussed.

An N.T.S.C.-type colour-television signal can be converted into a driving signal for a one-gun display tube without full demodulation of the sub-carrier signal. With the adoption of the PAL system for colourtelevisionbroadcasts in many countries of Europe the question arises whether similar methods can be devised for transcoding a PAL signal into a driving signal for dot-sequential display systems. The analysis of this problem leads to the conclusion that a slight modification of the PALswitching axis or a slight modification of the composition of the luminance signal is desirable. Practical conversion methods are discussed and some experiments are described. Employment of the standard PAL signal instead of the modified signal introduces small errors which are hardly observable. It is concluded that conversion of the PAL chrominance signal into a driving signal for one-gun display systems is well within the possibilities and does not require complex circuitry

This paper describes some experimental work in which the visual effects of incorrect decoding of the chrominance signals in colour television receivers were assessed by panels of observers. There are difficulties in changing circuit parameters in an actual receiver during a viewing session to simulate decoding errors. Apparatus was therefore constructed to produce exactly similar effects to those given by an incorrect receiver.Preliminary tests were conducted using this apparatus to show the effects of several different kinds of decoding error. For these tests the N.T.S.C. X/Z decoding system was used. Following these tests, the effects of amplitude errors in the output colour difference signals used to drive the display tube were investigated in greater detail. The later tests are therefore relevant to all of the three currently proposed systems. The results of these experiments were compared with other workers' theoretical calculations, thereby allowing some assessment to be made of the visual importance of the calculated colour errors.

A direct solution is presented for the turning points of the signal envelope, the heights being simply related to the amplitude and delay distortion of the channel.

A recently proposed method of measuring gain and delay inequalities in colour television is subject to ambiguities when applied to links having certain other linear distortions. A method of resolving these ambiguities is described.

It is suggested that simpler chrominance signals exist which correspond more closely to the confusion loci in tritanopia, and the sum and difference combinations of the colour-difference signals are listed as examples. The weighting factors for the colour-difference signals could also be simplified to unity and one half.

There has been interest recently in a color television system using a single camera tube in a modified Kell system in which the color information is modulated to high frequencies by dichroic spatial modulators placed in the image plane. Because the total allowable bandwidth for the signal is restricted, the overlap of the luminance and chrominance bands produces interference in the form of moiré patterns and color misinformation. This problem can be eliminated by including in the camera optics a low-pass filter that rejects the spatial frequencies causing the interference. In this paper, we discuss several types of phase filters and show that the rectangular wave phase grating, with a grating period of about 1 mm, offers the best performance. The optical transfer function and the filter characteristics of this optical element are discussed in terms of the grating parameters, and subjective tests are made on a prototype television system.