RU2246183C1 - Device for improving color transitions of television image - Google Patents

Abstract

FIELD: television systems; enhancing color definition of television image in horizontal direction.

SUBSTANCE: proposed device depends for its operation on linear processing of color-difference signal using calculation of spectrum and inverse filtering, as well as calculation of reverse spectral conversion effected in complete set of orthogonal Walsh functions with read-out numbers of signal spectral component functioning as sampling frequency. To this end color-difference signal is applied to several series-connected delay lines, delay time of each line being comparable with decomposition time of nominal decomposition element of television raster and total delay time of all delay lines being chosen to exceed pulse characteristic length of color channel as a whole.

EFFECT: enhanced quality of color image.

1 cl, 1 dwg

Description

The invention relates to television systems and can be used to increase the color resolution of a television image in the horizontal direction.

Devices for improving the quality of color images are known. The need to improve the quality of color images is due to the fact that color-difference signals in the color channels of modern color television systems are transmitted in a frequency band approximately five times smaller than the frequency band of the brightness channel. The color difference signal at the input of the matrix in the color block of the television receiver u _diff (t) is determined by the convolution integral

where u _in (t) is the "ideal" color difference signal at the input of the television system,

h (t) is the impulse response of the color channel as a whole,

* - mathematical sign of convolution of signals.

The length of the impulse response characteristic h (t) is of the order of 5 ... 7 image elements, as a result, the corresponding color resolution of the image turns out to be worse than the resolution of the luminance channel, and small color details of the image are perceived as colored spots with a length of several elements Images.

The simplest device that allows you to slightly improve color resolution is the inclusion in each color-difference channel of a high-pass filter on R, L, C chains [1]. A significantly greater effect is achieved using the device increasing the slope of the front of the color-difference signal [2]. The principle of operation is to increase the steepness of the fronts of color-difference signals by applying the principle of differential correction. To do this, the signal from the input amplifier is fed to the front detector, which consists of an amplifier, an inverter and a two-period rectifier. Positive pulses are formed at the output of the front detector, the amplitude of which depends on the steepness of the front (slice) of the color-difference signal pulses. In the comparator, these pulses are compared with the threshold voltage, and if their level exceeds the threshold value, then the logic unit signal acts at the output of the comparator, otherwise the logic zero signal. The voltage pulse at the output of the comparator is used to control the signal switch. During the action of the extended edge of the color difference signal, there will be no voltage at the output of the comparator. Therefore, the switch closes only after a certain period of time. With a high slope of the pulse edge of the color difference signal, a logic unit signal acts at the output of the comparator, and the signal switch completely commutes the input color difference signal to the output of the device. Thus, the known device [2] essentially performs nonlinear processing of a color difference signal by cutting off its slowly increasing or slowly falling part. Such clipping can degrade the color rendering quality, which is manifested in the form of fine-grained "ripples" in the color image. The known device [2] is implemented in modern televisions by using the K174X27 chip or its foreign counterpart TDM565, which contains, in addition to the channel for increasing the slope of the color difference front, a common delay channel for the brightness signal.

Thus, a disadvantage of the known device [2] is the insufficient correction of the color difference signal and the resulting additional distortions associated with the nonlinear nature of the processing of the color difference signal.

The purpose of this proposal is to improve the quality of the color image.

This goal is achieved by the fact that the device implements a linear method for processing a color-difference signal using inverse filtering methods in the basis of the complete system of discrete orthogonal Walsh functions. As is known from the theory of linear signal processing, the convolution spectrum of two signals is equal to the product of the spectra of these signals [3]. This means that if U _diff (f) is the spectrum of the difference signal u _diff (t) in the given basis of the complete system of orthogonal functions, U _in (f) is the spectrum of the ideal color difference signal u _in (t) in the same basis, and H ( f) is the spectrum of the impulse response characteristic h (t), then expression (1) is converted to

It follows from expression (2) that the spectrum of an ideal color difference signal

where k = 1 / H (f}.

отчетов спектральных составляющих [4]. Для этого цветоразностный сигнал подается на несколько последовательно соединенных линий задержки. Каждая линия задержки задерживает цветоразностный сигнал на время τ_з, соизмеримое со временем разложения номинального элемента разложения телевизионного растра. Общее число линий задержки N-1 выбирается таким, чтобы время задержки τ_зN превышало длительность импульсной передаточной характеристики h(t) канала цвета в целом. Выход каждой линии задержки подан на вход i-го инвертора, которым инвертируется полярность входящего сигнала. Первый вход каждого j-го сумматора 4 соединен с выходом усилителя 1. Каждый j-тый сумматор содержит N число выходов

при этом закон подключения i-го входа j-того сумматора к выходу i-й линии задержки или i-му инвертору определяется знаком i-го значения j-той функции Уолша. В результате на выходе j-того сумматора будет действовать j-тая компонента спектра Уолша от дискретных значений цветоразностного сигнала, действующего в данный момент на выходах линии задержки, а на выходах всех сумматоров будет действовать полный спектр U(j) этого цветоразностного сигнала. Каждый j-тый регулируемый усилитель, включенный на выход j-того сумматора, осуществляет усиление сигнала с коэффициентом K(j). Если этот коэффициент K(j) выбрать обратно пропорционально заранее вычисленному спектру Уолша H(j) импульсной передаточной характеристики h(t), то тогда на выходах регулируемых усилителей будет действовать спектр Уолша "идеального" цветоразностного сигнала, действующего на входе телевизионной системы цветоразностного сигнала, действующего на входе телевизионной системы в целом. Сигналы с выхода каждого j-того регулируемого усилителя поступают на входы выходного сумматора, где суммируются. Это эквивалентно вычислению обратного преобразования Уолша первого элемента изображения входного восстановленного цветоразностного сигнала. Так как входной цветоразностный сигнал по мере течения времени продвигается в последовательно соединенных линиях задержки от входа к выходу, соответствующим образом на выходе выходного сумматора будет осуществляться продвижение элементов изображения восстановленного цветоразностного сигнала. С помощью блока управления можно регулировать коэффициенты усиления регулируемых усилителей с целью оптимизации субъективного качества цветного изображения, удовлетворяющего конкретного телезрителя.Expressions (1), (2), and (3) are valid for spectra calculated using any complete system of orthogonal functions. In this device, the calculation of the spectrum and inverse filtering in accordance with equation (3), as well as the calculation of the inverse spectral transformation (the transition from U _in (f) to u _in (t)) is carried out in a complete system of discrete orthogonal Walsh functions. Moreover, since the Walsh transform is a discrete orthogonal transform, the role of the frequency f in it is played by numbers

reports of spectral components [4]. For this, a color difference signal is applied to several series-connected delay lines. Each delay line delays the color difference signal for a time τ _s , commensurate with the decomposition time of the nominal decomposition element of the television raster. The total number of delay lines N-1 is selected so that the delay time τ _s N exceeds the duration of the impulse transfer characteristic h (t) of the color channel as a whole. The output of each delay line is fed to the input of the i-th inverter, which inverts the polarity of the incoming signal. The first input of each j-th adder 4 is connected to the output of the amplifier 1. Each j-th adder contains N number of outputs

the law of connecting the i-th input of the j-th adder to the output of the i-th delay line or the i-th inverter is determined by the sign of the i-th value of the j-th Walsh function. As a result, the jth component of the Walsh spectrum from the discrete values of the color difference signal currently acting on the outputs of the delay line will act on the output of the jth adder, and the full spectrum U (j) of this color difference signal will act on the outputs of all adders. Each j-th adjustable amplifier, connected to the output of the j-th adder, carries out signal amplification with a coefficient K (j). If this coefficient K (j) is chosen inversely proportional to the previously calculated Walsh spectrum H (j) of the impulse response characteristic h (t), then the Walsh spectrum of the “ideal” color-difference signal acting at the input of the color-difference television system will act on the outputs of the controlled amplifiers acting at the input of the television system as a whole. The signals from the output of each j-th adjustable amplifier are fed to the inputs of the output adder, where they are summed. This is equivalent to calculating the inverse Walsh transform of the first pixel of the input reconstructed color difference signal. Since the input color difference signal advances in series-connected delay lines from input to output, the image elements of the restored color difference signal will advance accordingly at the output of the output adder. Using the control unit, you can adjust the gain of adjustable amplifiers in order to optimize the subjective quality of a color image that satisfies a particular viewer.

The structural diagram of the inventive device is presented in the drawing.

подключен к входу i-го инвертора 3. Каждая i-ая линия задержки 2 предназначена для задержки видеосигнала на время, соизмеримое со временем элемента разложения телевизионного растра. Выход усилителя 1 подключен также к первому входу сумматора 4. Общее число сумматоров 4 равно N. Каждый j-ый сумматор 4

имеет N входов. Закон подключения i-гo входа j-го сумматора 4 определяется i-ым значением j-той функции Уолша, которая может быть записана в виде рекурсивного уравнения:The color-corrector signal corrector contains an amplifier 1, the output connected to series-connected delay lines 2. The total number of delay lines N-1, the output of the i-th delay line 2

connected to the input of the i-th inverter 3. Each i-th delay line 2 is designed to delay the video signal for a time commensurate with the time of the decomposition element of the television raster. The output of amplifier 1 is also connected to the first input of adder 4. The total number of adders 4 is N. Each j-th adder 4

has N inputs. The connection law of the i-th input of the j-th adder 4 is determined by the i-th value of the j-th Walsh function, which can be written in the form of a recursive equation:

where k is a natural number,

p = 0 or p = 1,

2k + p = j - adder number,

i = 1,2 ... N is the adder input number.

Moreover, if the i-th value of the j-th Walsh function takes a value equal to 1, then the i-th input of the j-th adder 4 is connected to the output of the i-th delay line 2, and if the i-oe value of the j-th Walsh function takes value is 1, then the i-th input of the j-th adder 4 is connected by the output of the i-th inverter. The output of the j-th adder 4 is connected to the first input of the j-th adjustable amplifier 5. The second input of the j-th adjustable amplifier 5 is connected to the j-th output of the control unit 6. Each adjustable amplifier 5 is designed to amplify the input video signal with a gain specified with control unit 6. The output of the i-th adjustable amplifier 5 is connected to the j-th input of the output adder 7, and the output of the output adder 7 is connected to the input of the output amplifier 8. Each adder 4 and output adder 7 is designed to sum the input video signal ov.

The corrector of the color difference signal operates as follows.

The color-difference signal from the output of amplifier 1 is supplied to the first input of each adder 4 and to the input of series-connected delay lines 2. The video signal is delayed in each i-th delay line 2 for a time commensurate with the time of the television raster decomposition element, and is inverted in the corresponding i-th inverter 3. A video signal is supplied to the i-th input of each adder 4, either from the output of the i-th delay line if the Walsh function Wal (i, j) = 1, or from the output of the i-th inverter 3 if the corresponding Walsh function Wal (i , j) = - 1. Each j-th adder 4 summarizes the values of the input video signals taking into account the legitimate connection to the corresponding delay line 2 or inverter 3, that is, taking into account the law of change of the j-th Walsh function. Therefore, at an arbitrary moment of time, an electric signal proportional to the jth component of the Walsh function from a portion of the input video signal with a duration of N elements commensurate with the decomposition element acting at the output of the delay line 2 at this time will act at the output of the jth adder 4. An electrical signal proportional to the jth component of the Walsh spectrum from the output of the jth adder 4 is input to the jth adjustable amplifier 5. By selecting the gain of each jth adjustable amplifier 5, the frequency, in the spectral basis of the Walsh functions, is corrected for the video signal segment containing N decomposition elements. The adjusted frequency components of the Walsh spectrum from the output of each j-th adjustable amplifier 5 is fed to the j-th input of the output adder 7. The output adder 7 sums the electrical signals proportional to the Walsh spectral components, which is equivalent to calculating the first corrected decomposition element. The signal from the output of the output adder 7 is fed to the input of the output amplifier 8.

Sources of information

1. S.A. Elyashkevich, A.P. Leskin. TVs ZUSTST, 4USUT, 5USTST, device, adjustment, repair. MP "Symbol-R", M., 1993, section 4.7. Color Modules, page 62.

2. D.V. Voytsekhovsky, A.E. Peskin. Amateur video and audio devices for color TVs. M. "Symbol-P". 1994, p. 5, paragraph 2. Device for improving color transitions (application of the K174XA27 microcircuit and its analogs in decoders), Fig. 2.2. The structural diagram of the chip K174XA27 and its analogues.

3. M.M. Miroshnikov. Theoretical foundations of optoelectronic devices. M .: Mechanical engineering, 1977, p. 338., subsection 4.6. Convolution spectrum theorem.

4. X. Harmut. Theory of sequential signals. M .: Mir, 1980

Claims (1)

A device for improving the color transitions of a television image containing an amplifier, an output amplifier, N-1 inverters and a control unit, characterized in that an N-1 delay line, N adders, N adjustable amplifiers and an output adder are additionally introduced, the amplifier output being connected to the first input of the Jth adder

and input from series-connected delay lines, and the output of the i-th delay line

connected to the i-th input of the j-th adder either directly, if the values of the i-th Walsh function, the complete system of orthogonal Walsh functions of size N, at the j-th point takes a value equal to 1, or through the i-th inverter, if the value i -th Walsh function at the jth point takes a value equal to -1, while the output of the jth adder through the jth adjustable amplifier is connected to the jth input of the output adder, the output connected to the input of the output amplifier, and the control input j- An adjustable amplifier is connected to the corresponding output of the control unit.