SU1345378A1 - Shaper of color-differential signals of secam decoder - Google Patents

Abstract

The invention relates to television technology and improves the accuracy of forming color difference signals. The device contains a band-pass filter 1, a multiplier 2, a high-frequency predistortion corrector 3, switches 4 and 7, a frequency demodulator (RR) 5, a low-frequency predisposition corrector 6, a delay line 8, a control driver 9, averaging unit 11 and reversible counter 12. Automatic adjustment of the subcarrier levels at the input of BF 5 improves the accuracy of demodulation of the chrominance signal by reducing the effect of the level of the subcarrier on BH5 operation. 1 Cp, files, 2 ill. Bxoff in-CO 4 cl with 00 C: fc7pt2) fie.1

Description

The invention relates to television technology and can be used in decoding devices of television receiving equipment with digital signal processing.

The purpose of the invention is to improve the accuracy of forming color difference signals.

FIG. 1 shows a structural electrical circuit of a driver of color difference signals of a SECAM decoding device; FIG. 2 is a structural electrical block averaging scheme.

The driver of the color difference signals of the SECAM decoding device (Fig. 1) contains a band-pass filter (PF) 1, a multiplier 2, a high-frequency predistortion corrector 3 (KBIT), a second switch 4, a frequency demodulator (BH) 5, a low-frequency predistortion corrector 6 (KNP), the first switch 7, the delay line 8, the driver of the control signals 9, the compensation unit 10, the averaging unit 11 and the reversible counter 12.

The averaging unit 11 (FIG. 2) contains the first adder 13, the first register 14, the first delay unit 15, the second adder 16, the second delay unit 17, the third adder 18, the third delay unit 19, the quarter adder 20, the second register 21 and the comparator 22

The shaper color-difference signals decoding device SECAM works as follows.

The full color television signal after analog-digital conversion is fed to the input of the IF 1, in which the spectral and chromaticity spectra are pre-divided, including the constant component separation. From the output of the PF 1, the chroma signal during the active part of the line through the multiplier 2, KVP, the second switch 4 is fed to the input of PD 5, which digitally demodulates the frequency-modulated chroma signal. From the output of BF 5, the color-difference signals alternating through the line are fed through KNP 6 to the inputs of the first switch 7 directly and through the delay line 8, in which a delay of one line is made. The first switch 7 is controlled by pulses of a half-line frequency along the control

the input, with the result that the color difference signals of red and blue are formed at its outputs, from

which, by matrixing, the signals of primary colors (red, green and blue) can be obtained. Line -8 delay is clocked on the control input by pulses from

first exit shaper 9.

Under the influence of the signal at the control input of the second switch 4, the input of the FD 5 is connected to the output of the multiplier 2 through the compensation unit 10

(bypassing the COI 3). This makes it possible to exclude the effect of transients in FEC 3 during the measurement of the amplitude of the color subcarrier load.

. The signal from the second output of PD 5, proportional to the amplitude of the flash, through averaging block 11 controls the reversing counter 12, the output code of which is fed to the first input of multiplier 2 and determines its transmission coefficient, allowing to maintain a constant level of the subcarrier signal at the input of the PD 5. Block 10 compensation has a transmission coefficient equal to the transmission coefficient at the center frequency (tuning frequency).

The averaging unit 11 allows to obtain the required noise immunity.

the automatic control system formed by blocks 2, 4, 5, 10, 11 and 12, and works as follows (Fig. 2).

The first adder 13 and the first register 14 form the accumulating adder and averaging the amplitude of the flash during the time of its effect on the input of the device. Due to the fact that, to ensure the required noise immunity, this is not enough, in block 11, the output signal of the accumulating adder is additionally averaged over

eight consecutive lines, which is carried out in blocks 15-20. The output of the fourth adder 20 passes (through the first inputs of the adders 16 and 18) the signal of the current line, and.

through the second and third adders 16 and 18, and the third block 19 of the delay, having a delay time equal to the duration of two lines, the signal of the previous line, etc. Given that the first 15 and second, 17 delay blocks have delay times of four and two lines, respectively, the output of the fourth adder 20 produces a signal proportional to the arithmetic average of the input signal over a time equal to eight horizontal periods.

The second register 21 is intended to fix (latch) the output code of the fourth adder. Comparator 22 compares the input signal with a fixed value that determines the gain of multiplier 2 (Fig. 1). The outputs of comparator 22 (More and Less) directly control the reversing counter 12.

Auto-adjusting the return voltage of the subcarrier at the BH input allows to increase the accuracy of signal demodulation

chrominance (color accuracy (Red color) contains successively difference signals) due to decreased first adder, first influence of the subcarrier level on. BH work 5.

a register, a first delay unit, a second adder, a second delay unit, a third adder, a third delay unit, a fourth adder, a second register and a comparator, the output of which is the output of the averaging unit, the combined second inputs of the first and second adders are connected to the output of the first register, and the second inputs of the third and fourth adders are connected to the inputs of the second and third delay units respectively, the combined control inputs of the first and second registers and the first, second and third delay blocks are pack Aulus yuschim averaging the input block, and the first input of the first adder is input to the averaging unit.

Claims (2)

Claim 1. Shaper of color-difference signals of the SECAM decoding device containing a high-frequency predistortion corrector (FOC), serially connected frequency demodulator (BH), low-frequency predistortion corrector (KNP), a delay line and the first switch, the second input of which is connected to the output of the PNP, first and second outputs The outputs are, respectively, red and blue color difference signals, and the control input is the input of half-line frequency pulses, the driver of the control signals, whose input is The input is a horizontal frequency pulse, and the first output is connected to a control input of a delay line, characterized in that, in order to improve the accuracy of generating color difference signals, a band-pass filter is inserted in it, as well as a series-connected averaging unit, a reversible counter, a multiplier, a block compensation and the second switch connected between the second output and the BF input, the second input of the multiplier is connected to the output of the bandpass filter, the input of which is the input of the video signal, KVP is connected between the output of the multiplier and the second input of the second switch, and the second and third outputs of the control signal generator, are connected respectively to the control inputs of the second switch and the averaging unit. 2. The former according to claim 1, characterized in that the unit Red has a successively connected first accumulator, the first thirty 35 40 a register, a first delay unit, a second adder, a second delay unit, a third adder, a third delay unit, a fourth adder, a second register and a comparator, the output of which is the output of the averaging unit, the combined second inputs of the first and second adders are connected to the output of the first register, and the second inputs of the third and fourth adders are connected respectively to the inputs of the second and third delay blocks, the combined control inputs of the first and second registers and the first, second and third delay blocks are pack Aulus yuschim averaging the input block, and the first input of the first adder is input to the averaging unit. From 5 From 9 FIG. 2