SU803875A3 - Method of transforming "sekam" colour television system sygnals - Google Patents

Abstract

A plurality of SECAM color-T.V. signals are -to be mixed. Each comprises an AM luminance component and an FM color component. For each individual signal, the color component is separated from the luminance component, frequency-demodulated, amplitude-modulated, and then superimposed upon the respective luminance component to form a frequency multiplexed modified signal. The plurality of thusly modified signals are then mixed using a single mixing channel. The mixed luminance component and the mixed color component are separated on the basis of frequency, and the mixed color component is amplitude-demodulated,then frequencymodulated, and then superimposed upon the mixed luminance component, to yield a SECAM color-T.V. signal which constitutes a mix of the original signals.

Description

one

The invention relates to television and can be used in devices mixing color video signals in color television systems SECAM.

There is a known method of mixing SECAM color television signals based on the frequency separation of each color television signal into luminance signals and chrominance signals, the formation of color difference signals, the summation of signals from variable} weighting coefficients, the coding of color-intensity signals and the formation of a full color television signal l

However, with the known method of mixing color TV signalings, significant color distortions are observed.

The purpose of the invention is to reduce color distortions when mixing color television signals.

To do this, in the method of mixing the color television signals of the SECAM system based on the frequency separation of each color television signal into luminance signals and chrominance signals, shaping color difference signals, summing the signals with variable weighting factors, encoding color difference signals and generating the full color television signal after generating color-difference signals form the carrier frequency, which is modulated in amplitude by the color-difference signals of each of the signals fishing color television received signals are summed with the luminance signals of each of the color television signal, all resulting signals SAC, 1iruyut with variable weight koeffitsients1mi, t derivatives frequency division sigNssha obtained on a color television luminance signal and a chrominance signal component, which is modulated in amplitude.

FIG. 1 shows the structural electrical circuit of the device for implementing the proposed method; in fig. 2 - the frequency spectrum of the channel brightness and color.

The device for implementing the method contains two channels, each of which consists of the detector 1.1, the first filter 2 and the bottom 2. one of amplitude modulator 3 and 3

second filter 4 and 4 / low pass and adder 5 and 5, as well as generator b, mixer 7, low pass filter 8 / high pass filter 9, amplitude demodulator 10, frequency modulator 11 and cyiyMaTop 12.

In the PAL, NTSC and SECAM color television systems, the information about the light is transmitted in the frequency range, the frequency information. At the same time, the color information is modulated onto the color subcarrier, which is adjectively superimposed on the luminance signal containing the luminance information. According to the SECAM standard, the color subcarrier is partially modulated with the first color difference signal during one line and with the second color difference signal during the next line. In this case, the color subcarrier has different rest frequencies, each of which corresponds to one of both color difference signals.

FIG. 2 shows the frequency spectrum of luminance and color information for a luminance channel and for a chrominance channel. The solid line indicates the frequency range for the luminance signal. In this frequency range from O to approximately 5 MHz, there is also the frequency range of the chromaticity channel (indicated by dotted lines). Narrowband color channel lies in the upper frequency range of the luminance signal. Frequencies 4, 25 and 4.4 MHz are the quiescent color subcarrier for the color signal in the color channel. Color information is transmitted with frequency modulation. For a process of shifting several SECAM color video signals, a frequency modulated color signal is separated from the signal and converted into an amplitude modulated color signal. This transformed signal is frequency-packed with an amplitude-modulated luminance signal. At the same time, part of the frequency range in the luminance channel, in which the color channel is located according to the CECAM standard, is suppressed and transmitted in an amplitude modulated form over the frequency range of the original luminance channel at approximate MHz (dashed line). This signal can be processed single-channel in one mixing process.

A device for implementing the method works as follows.

We suggest that the 5ECAM-PBA5 signals lie on the terminals 13 and 13, the FBAS and FBAS2 signals must be additively mixed in the mixer 7. For this, the FBAS signal is supplied to the decoder 1, which decodes the color signal of the SECAM system into the signals of brightness and color. The luminance signal y through a low-pass filter 2 with a cut-off frequency of approximately 4 MHz is fed to the input of adder 5. A video signal of an alternating frequency signal depending on the frequency of the sequence of color difference signals V-U and Ry is modulated by amplitude in modulator 3 and through another low-pass filter 4 with a cut-off frequency of approximately 8 MHz is fed to another input of the adder 5. Amplitude modulator 3 is fed to the signal of the subcarrier approximately b MHz generated in the generator b. The amplitude modulator 3 is made with a unified functional unit of the balanced ms-dultor so that the amplitude-modulated signal is output with suppressed subcarrier. The frequency of the subcarrier generator 6 is horizontally frequency linked by means of a clock signal in such a way that a half-line offset occurs. The signal removed from the output of the adder 5, consisting of the amplitude modulated amplitude signal and the modulated chroma amplitude signal, is fed to the input of mixer 7. To another input of mixer 7, a properly converted FBAS signal is taken Out of the mixer 7 output, the signal obtained during the mixing process split by a low-pass filter B, having a limiting frequency of approximately 4 MHz, is opted for by a luminance signal Y and by means of a filter 9 having a limiting frequency also of approximately 4 MHz , on the chroma signal. Signal separation can also be done with a comb filter. Further, the amplitude modulated chrominance signal is demodulated in demodulator 10. The resulting variable line-by-line with the sequence of video frequency color difference signals V-V and R-y, and the like. modulated in frequency in modulator 11 and in frequency-modulated form superimposed on luminance signal Y in adder 12. At output 14 of adder 12, a linear combination of the input signals FBAS and

Since the aplitud-modulated signal from the supplied subcarrier is demodulated, the demodulator 10 contains a synchronous demodulator to which the subcarrier signal generated by the generator b is fed. Between the amplitude modulators 3, 3, ... and the amplitude demodulator 10, devices are provided for adjusting the phase, which allow the phase adjustment of the corresponding subcarrier signal.

A SECAM-specific color subcarrier signal is applied to input 15; consisting of a line-wise sequence of both frequencies at rest of the color subcarrier. This signal, in addition, switches in phase according to the rhythm adopted in the SECAM standard. The specific SECAM color subcarrier signal is used to synchronize the frequency modulator 11 during the horizontal haitzion interval.

Claims (1)

Invention Formula A method of mixing SECAM color television signals based on the frequency separation of each of the color television signals into luminance signals and chrominance signals, the formation of color difference signals, the summation of signals with variable weighting coefficients, the coding of color difference signals and the formation of a full signal color television, characterized in that, in order to reduce color distortions while mixing color television signals, after forming color difference signals, a carrier frequency is formed, which is modulated in amplitude by the color difference signals of each color television signal, the received signals are summed with the brightness signals of each color television signal , all resulting signals are summed with variables; weighting factors, produce frequency separation of the received signal in color of the television signal at a luminance and chrominance signal component, which is modulated in amplitude. Sources of information taken into account in the examination 0 1- B.M. Pevzner Color television systems. L., Energie, 1969, p. 114 (prototype).