RU2002378C1 - Decoder of secam system - Google Patents

Description

The invention relates to the field of color television, namely to decoding devices, i.e. devices in which the color television signal is converted by the SECAM system into three primary color signals (red R, green G and blue B) for controlling color display devices;

SECAM decoders are known to perform these functions. These decoders comprise a luminance channel, a color channel, and a matrix signal converter. The input signal SECAM enters simultaneously into the channel of brightness and color channel. The brightness signal from the output of the brightness channel and two color-difference signals (red R-Y and blue B-Y) are fed to the inputs of the matrix converter, which forms the required signals R, G, and B.

In the luminance channel, the color components are suppressed (or substantially attenuated) by the notch chain. In the color channel, the luminance components are suppressed using a band-pass filter, a high-frequency predistortion correction circuit, and an amplitude limiter. Then, using the delay line to the scan line and the toggle switch, the color difference signal lines transmitted by transmission are restored by repeating, so that two continuous sequences of signal lines R-Y and B-Y are formed at the outputs of the color channel.

The described circuit is standard. Other schemes are distinguished by the color channel arrangement, although in all cases it performs the described functions of repeating the missing color difference lines.

All known SECAM decoders have two drawbacks. The first is that when transmitting horizontal or inclined color borders and structures, color inter-flicker flickers occur. A second disadvantage is that the color and luminance components of the image are vertically aligned on one line of the full frame.

Closest to the proposed technical solution, selected as a prototype, is a SECAM decoder. This decoder contains a luminance channel with a color signal detector connected to the first input of the matrix converter by an output, and a color channel, the outputs of which are connected to the other two inputs of the matrix converter. The color channel contains sequentially included high-frequency predistortion corrector, an amplitude limiter, a color signal frequency detector and a low-frequency predistortion corrector. One is connected to the output of this corrector.

the input of the cross over switch directly, and the other through the delay line of the CCD type to the scan line, The switch alternately connects either input or each of its two outputs in rows

the output of the delay line so that continuous sequences of color difference signals R-Y and B-Y are formed at its inputs. Color interline flicker also occurs in this decoder during transmission

horizontal or inclined color borders and structures, and the misalignment of the color and brightness components of the image vertically by one line of the full frame due to the relative delay of color difference components by half the period of the line resulting from the use of a delay line in the decoder.

In FIG. 1 is a vertical time section of a television image, i.e. section of consecutive fields by a plane perpendicular to the direction of horizontal scanning. Here, the white circles indicate the lines of the R-Y signal, and black - the lines of the B-Y signal; vertical lines connect sections of the line to the field. In the decoder, each transmitted line RY and BY is repeated to restore the lines missed during transmission. In this case, an inaccurate restoration of the transmitted color difference components takes the form of sequences of pairs of identical lines, and between these pairs of lines line flicker distortion. This is an illus

vertical-time diagram

in FIG. 2. Diagram a shows the line samples of the transmitted signal (for example, R-Y for one gender). Diagram b shows the operation of a conventional decoder.

5 It can be seen that, in the vertical direction, jumps in the color difference component are formed. These jumps change their character in successive fields and thereby cause flicker.

0 FIG. 1 also explains the occurrence of vertical misregistration between the luminance and color difference components. The repetition (with a delay of one period of lines) of the color-difference signal leads to the fact that the central line of the pair of lines (transmitted and repeated) is shifted down by one step of lines in the frame, and this offset cannot be compensated by the delay of the brightness signal, since the required delay would be half period

lines and its introduction would lead to an unacceptable shift of the luminance component by half the horizontal width of the frame.

The aim of the invention is to increase the degree of suppression of distortion.

This goal is achieved in that in the decoding device of the SECAM system. comprising a luminance channel, a color channel, and a matrix converter, the luminance channel input and the color channel input of which are combined and are the input of the full color television signal, and the first, second, and third outputs of the matrix converter are the output signals of red, green, and blue, three delay lines per line and two adders are introduced, while the output of the brightness channel through the first delay line is connected to the output of the brightness signal of the matrix converter, and the first output of the color channel connected to the input of the color-difference signal RY of the matrix converter through a second delay line and a first adder connected in series, to the second input of which a first output of the color channel is connected, and the second output of the color channel is connected to the output of the color-difference signal BY of the matrix converter through the third delay line connected in series and the second adder, to the second input of which the second output of the color channel is connected.

Smoothing vertical discrete filters are introduced into the color-difference signal chain, due to which the color-difference signals missed during transmission are formed as the average values of adjacent transmitted lines (Fig. 2c), which leads to a significant weakening of color line-to-line scintillations. At the same time, the action of these filters leads to a shift of the color difference components vertically by another line of the full frame. In this case, the total displacement is now two lines of a full frame, and it is electrically completely compensated by the delay line for one period of lines introduced into the luminance signal circuit.

In FIG. 1 shows a vertical-temporal section of strings of transmitted color difference signals; in FIG. 2 is a vertical-time diagram for rows of a single floor; FIG. 3 is a structural diagram of the proposed decoder.

The proposed decoder has an input to which the luminance channel 1 and the color channel 2 are connected. The output of the luminance channel 1

through the delay line 3 to the line is connected to the input of the brightness signal of the matrix converter 4. One output of the color channel 2 through the delay line 5 to the line and the adder 6 is connected to the input of the color-difference signal RY of the converter 4. The second input of the adder 6 is connected to the input of the delay line 5 The second output of the color channel 2 through the delay line 7 and to the adder 8 is connected to the input of the color difference signal BY of the converter 4. The second input of the adder 8 is connected to the input of the delay line 7. The outputs of the converter 4 serve as the outputs of the decoder.

The decoder works as follows.

The full color television signal via the SECAM system enters the luminance channel 1 and the color channel 2. In the luminance channel 1, color components are suppressed in this signal, and a luminance signal is generated at its output. In color channel 2, luminance components are suppressed. The color difference signals missed by the transmission line are restored by repeating using the delay line per line and the toggle switch, which are included in the color channel 2 (not shown in Fig. 3).

Thus, two continuous sequences of strings of color difference signals R-Y and B-Y are formed at the output of chrominance channel 2. These sequences from the outputs of chrominance channel 2 go directly to one of the inputs of adders 6 and 8, and to their other inputs respectively through delay lines to lines 5 and 7. As a result of the action of vertical filters formed by adders 6, 8 and delay lines 5 and 7 that are missed during transmission of a color-difference signal string are restored as the average values of transmitted adjacent rows. From the outputs of adders 6 and 8, the color difference signals R-Y and B-Y are fed to the matrix converter 4, which also receives the brightness signal Y from the output of the delay line 3. The matrix converter converts the signals Y. R-Y and B-Y into the required signals of the primary colors R, G, B.

Various implementation schemes of the proposed decoder are possible. A preferred embodiment is a circuit based on the use of CCD delay lines. These delay lines are designed to delay video signals and are integrated circuits in design. A total of 4 such lines will be required: one in the color channel and three in the input according to the proposed solution. Adders can be implemented

using a resistor circuit for adding currents.

A fully or partially digital implementation of the proposed decoder is also possible. In this case, delay lines 3, 5, 7 are implemented using random access digital storage devices, and arithmetic integrated circuits included in standard series of logical integrated circuits are used as adders b and 8. Conventional integrated circuits for analog-to-digital and digital-to-analog converters are used to transition from an analog signal to a digital signal and vice versa.

In any embodiment, the proposed improvement of the decoding device causes a relatively small complication, justified by the improvement in image quality in VCRs and televisions.

In the proposed decoder, thanks to the input links m of the vertical filter

Claims (1)

The claims A SECAM SYSTEM DECODING DEVICE comprising a luminance channel, a color channel and a matrix converter, the inputs of the luminance and color channels of which are combined and are the input of the full color signal of the television, and the first, second and third outputs of the matrix converter are respectively the output of red signals , green and blue colors, characterized in that, in order to increase the degree of suppression of distortion, three delay lines per line and two adders are introduced, while the output of the brightness channel through the first delay line LCD connected to signal input0 5 0 The restoration of the missing lines is not done by repeating, as is done in the known decoders, but by interpolating the transmitted adjacent lines, whereby the original sequence of color-difference signal lines is more accurately restored and a higher degree of distortion suppression is provided. Since with such filtering the total delay of color difference signals corresponds to exactly one period of lines (in the prototype, half of the period of lines), it can be compensated by the delay line introduced between the brightness channel and the matrix converter and thereby eliminate the distortions caused by the vertical combination of brightness and color difference component images. (56) Khokhlov B.N. Decoding devices for color televisions. -M.: Radio and Communications, 1987. French Patent No. 213794, cl. H 04 N 9/00, published. 12/29/72. the brightness of the matrix converter, the first output of the color channel is connected to the input of the color-difference signal R - Y of the matrix converter through a second delay line and a first adder connected in series to the second input of which the first output of the color channel is connected, and the second output of the color channel is connected to the input of the color-difference signal B - Y matrix converter through sequentially connected the third delay line and the second adder, to the second input of which the second output of the color channel is connected. a / i at -H FIG. 2 ce # 0s pg / e.Z