SU1124451A1 - Device for suppressing noise in reproducing channel of video tape recorder - Google Patents

Abstract

1. A device for suppressing noise in a replay of a video recorder, which contains a generator of control pulses, the input of which is an input of a video signal, in order to increase the signal-to-noise ratio. the first and second delay lines connected in series, the first controlled adder, the buffer amplifier and the second controlled adder, and a third delay line, the input of which is connected to the second output of the buffer amplifier, and the output connected to the second input of the second controlled adder, and the second input of the first controlled adder is connected to the output of the first delay line, and the control inputs of the first and second controlled adders are connected to the output of the control pulse generator.

Description

2. The device according to claim 1, about tl and each one in that each controlled adder contains the first, second, and third inverters, the emitter follower, the key, the first and second current generators, and the inputs of the first inverter and the emitter follower are combined and The first input of the controlled adder, the input of the second and the first input of the third inverter are combined and are the second input of the controlled adder, the outputs of the first, second and third inverters are combined and are the output of the controlled adder, the output of the first current generator dklyuchen to the input power, emitter-follower, a second current generator connected to the control input of the third inverter between the output of the emitter follower and the second input of the third inverter is enabled key whose control input is a control input of the controllable adder

3, The device according to GG, 1, characterized by the fact that the generator of control of pulses contains a filter plug connected in series, a differentiation unit, an amplifier, a level shift block, a delay element, a peak detector, a first comparator, an OR element and a pulse shaper connected in series between the output of the peak detector and the second input of the OR element, the inverter and the second comparator, as well as the key connected between the output of the delay element and the common bus, the control input of the key connected to the output of the OR element, and a third level shift unit outputs are connected to second inputs of the first and second Koi mapaTopoB, filter-tube inlet is input generator control pulses, and the output of the pulse shaper - controlled oscillator output pulses constituents.

The invention relates to a technique of television and can be used in video recorders and when transmitting a video signal over a communication line.

A noise suppression device is known comprising first and second series-connected delay lines with a delay time equal to the period of the trace horizontal sync pulses, a first adder connected to the outputs of the first and second delay lines, a subtraction circuit connected to the output of the first delay line and to the output of the first adder , a diode limiter connected to the output of the subtractor, a second adder connected to the output of the first adder and to the output of the diode limiter; a limiting threshold adjustment circuit connected to a diode limiter, a low-pass filter and a delay circuit whose inputs are connected to the output of the second adder, and the outputs are connected to the input of the second subtraction device, the second diode limiter and the input

connected to the output of the second subtractive device., a second limiting threshold adjustment circuit connected to the second diode limiter, a third total / sp, whose inputs are connected to the output of the second diode limiter and to the output of the low-pass filter lj.

However, such a device requires two very high quality ultrasonic delay lines with a delay value equal to the period of the horizontal sync pulses. When processing a full color television signal in a diode limiter, nonlinear distortions of the color subcarrier | When working with a SECAM-encoded television signal, amplitude modulation of the color subcarrier frequency occurs at the output of the first adder. Output full color video signal is subject to distortion.

Closest to the proposed technical solution is a device for reproducing a VCR in the output channel, which contains a generator of control pulses whose input is a video signal input, a high-pass filter and a low-pass filter, a building block and a summatr, whose inputs are connected respectively to the filter output. low frequencies and with the output of the gating unit, the input of which is connected to the output of the control pulse generator 2,

In this device, in the presence of parts with constant luminance, only a low-pass filter is turned on, which eliminates the chrominance subcarrier in the output signal, i.e. the device is able to clear only the black and white television signal from noise. In addition, with multiple switches of the 1 band of the channel band within the active part of the line, the low-frequency components of the signal and luminance transmitted through the channel in the narrow band mode are shifted relative to their nominal position in the direction of delay, i.e. The device has a distortion type difference in delay.

The purpose of the invention is to increase the signal-to-noise ratio.

The goal is achieved by the fact that the device noise suppression in the playback channel; video recorder, containing the control pulse generator, whose input is the video signal input, the first and second delay lines connected in series, the first controlled adder, the buffer amplifier and the second controlled adder, as well as the third delay line which input is connected to the second output the buffer amplifier, and the output is connected to the second input of the second controlled adder, the second input of the first controlled sum of the torus is connected to the code of the first delays, and the control inputs of the first second and second controlled adders are connected to the generator output of the control for cich pulses.

In addition, each controlled adder contains a first, second and third inverters, an emitter follower key, a first and second current generators, and the inputs of the first inverter and the emitter follower are combined and are the first input of the controlled adder, the second input and the first input

The third inverters are combined and are the second input of the controlled adder, the outputs of the first, second and third inverters are combined and are the output of the controlled adder, the output of the first current generator is connected to the power input of the emitter follower, the output of the second current generator is connected to the control input of the third inverter The key is switched on between the emitter follower output and the second input of the third inverter, the control input of which is the control input yjv of the target adder.

The control pulse generator contains a filter plug connected in series, a differentiator amplifier, a level shift block, a delay element, a peak detector, a first comparator, an OR element, and a pulse shaper connected in series between the output of the peak detector and the second input of the OR element, the inverter, and the second comparator , as well as a key, switched on by the output of the delay element and the common bus, and the control input of the CLNA is connected to the output of the OR element, the second and third outputs of the level shift block are With the second inputs of the first and second comparators, respectively, the input of the filter plug is the input of the control pulse generator, and the output of the pulse shaper is the output of the control pulse generator.

The drawing shows a structural electrical circuit of a device for suppressing yum in the playback channel of a VCR.

The 1puma suppressor in the playback channel of the VCR contains the first 1 and 2 sec delay lines, the first controlled adder 3, the buffer amplifier 4, the third delay line 5, the second controlled adder 6, and the control pulse generator 7.

Each control adder contains the first 8, second 9, and third 10 inverters, an emitter follower, 11, a key 12, a first1, 13, and a second 14 current generators.

The control pulse generator contains a filter plug 15, a differentiation unit 16, an amplifier 17, a level shifting unit 18, a delayed element 19, a peak detector 20, a switch 21, an inverter 22, the first 23 and a second 24 comparators, an ILR element 25 and a driver 26 pulses. The noise suppression device in the playback channel of the video recorder operates as follows. A reproducible full color video signal is fed to the input of the first delay line 1 and to the input of the control pulse generator 7. In the first video delay line 1, the signal is delayed by a time slightly longer than the propagation delay time of the signal generator 7 of control pulses. The delayed video signal from the output of the first delay line 1 is fed to the second input of the first controlled adder 3 and to the input of the second delay line 2. The delay time of the second delay line 2 is TOR + Tav where Tgj is the frequency period of the color subcarrier in the red line; Tgg is the period of the quiescent frequency in the color sub-subsector on the blue line. The signals from the input and output of the second line 2 of the delay signals are the direct and delayed signals that arrive at the second and first inputs of the first controlled adder 3, respectively. In the first controlled sum of the matrix 3, the delayed signal arrives at the input of the first inverter 8 and the input of the emitter follower is 11, and the direct (non-delayed) signal is delivered to the inputs of the second 9 and third inverters. The modes of the constant emitter follower 11 and the third inverter 10 are set using the first 13 and second 14 current generators. With the open key 1 connected between the emulator 11 and the third inverter 10, the transmission factor of the third inverter 10 is much less than 1) , since the B emitter circuit of the transistor, which surrounds its inverter, includes a second current generator 14, greater output resistance, Also m gde less than one and the transmission coefficient of the signal that is supplied through the emitter follower 11 ne first output equal adder 3, since there is a break in key 12 in the direct video signal transmission circuit. Therefore, when key 12 is open, the video signal is output to the output of the first controlled adder 3 via the first inverter 8 and the second inverter 9, and in this case the first control This adder 3 works as an adder of two signals. Since the input signals are shifted relative to each other in the second delay line 2, the output sum signal has a non-linear frequency response that corresponds to the output of U co5COS, and the delay time of the output signal relative to the input is half the delay time of the second delay line 2, i.e. In the case of a closed key 12, the emitter follower 11 ,, key 12, the third inverter 10 together with the first 13 and second 14 current generators form a differential amplifier circuit, in which the transmission coefficient of both the inverting and non-inverting inputs is equal to that of the first 8 and the second inverter 9- Thus, when the key 12 is closed, the output of the first controlled adder 3 subtracts the signals at its inputs. With the transfer coefficient of the emitter repeater 11 and the third inverter 10, which form the differential amplifier equal to the transfer ratio of the first 8 and second 9 inverters, the output of the first controlled adder 3 has a zero level coming to the first input and twice the signal coming at the second entrance. The resultant frequency response of the first-controlled adder 3 is linear. There is no output delay for the input signal. When the transmission coefficient of the first inverter 8, the second inverter 9 and the system forming the differential amplifier is 0.5, the transmission coefficient of the first controlled adder 3 is 1. At the same time, the transients associated with the switching of the key 12 are passed to the output of the block level - 6 dB (which is associated with video switching only in the channel, the differential amplifier, whose transmission coefficient is 0.5), i.e. provides additional suppression of transients superimposed on the video signal. Through the buffer yci 4, the signal goes to the first input of the second controlled adder 6 and to the input of the third delay line 5, which is similar to the second delay line 2. From the output of the third delay line 5, the signal arrives at the second input of the second controlled adder 6. Its operation is similar to the operation of the first controlled adder 3, Since the first input of the second controlled sum 6 of the matrix 6 receives a direct signal, and the second - delayed signal the third delay line 5, in the case of forming a linear frequency response, the output signal is delayed relative to the input signal for a time equal to the delay time of the signal in the third delay line 5, and in the nonlinear frequency response form of the output minutes otno 1sitelno input signal is delayed by a time equal to half the signal delay in the third delay line 5. Thus, when forming a linear frequency response using the first 3 and second 6 controlled adders, the output signal of the device has a delay determined by the delay time of the signal in the third delay line 5, and when generating a nonlinear frequency response, the delay of the signal is,, t. Since the dwell time of the second 2 and third 5 delay lines is the same. Thus, in both modes of operation of the device, there is no change in delay of the output signal, which ensures that there is no distortion of the signal of the clock type. Uco5 (ut | 2) tecs cot g 518 The second max-g frequency response falls on the value under the 1 frequency carrier of the chroma signal. The band pass characteristics ensures the passage of the lower and upper sideband of the color subcarrier. In order to provide the necessary linear frequency response in the deviac: and color subcarrier frequencies, the buffer amplifier 4 provides for frequency correction in the frequency deviation region of the color subcarrier. Since the signals at the inputs of each of the two frequency characteristic formation blocks are shifted by a time equal to the period of the subcarrier frequency, when switching the key included in each controlled adder, there is practically no phase shift of the subcarrier frequency, therefore, there is no distortion of the type and on a color video monitor at the signal switching point. The frequency band of the full color video signal, encoded by the SECAM system, is 6.5 MHz. The value of this frequency with a sufficiently high accuracy coincides with the second minimum of the frequency response of the device. At the same time, it turns out that the area bounded by the Nonlinear Frequency Characteristic is two times smaller than the area bounded by the linear frequency response in the 06.5 MHz band. In this case, the gain in the signal-to-noise ratio B of the output signal of the device will be 3 dB. When multiple re-recordings of a non-signal are carried out, a ft K on a video recorder, the multiplication of the ordinal, nat frequency characteristics from one rewriting process to another will occur. When playing subsequent copies of the resultant, the frequency response from one copy to another will be narrowed. Calculations show that when you play the first copy, the total gain will be 3 dB, and when you play the third copy - 4 dB. In generator 7 of control pulses, sections of the video signal with a signal slope above a certain value are made, determined by | the slope of the frequency response of the differentiation unit 16, the fixing of such sections is made taking into account the noise level in the input video signal.

The operation of the generator 7 control pulses is carried out in the following way, ..

The video input signal enters the filter plug 15 input, in which the frequency of the chrominance signal rises, the brightness component of the video signal, which is the output signal of the filter plug 15, is fed to the differentiation unit 16. Depending on the shape of the gradient. in the input full video signal, the output of differentiation unit 16 may be positive polarity, negative polarity, or may be polarized. Thus, for example, the sin T pulse at the output of differentiation unit 16 is converted into a opposite polarity. A differentiated signal is fed to the amplifier 17, the dynamic solution and the value of the transfer coefficient of which is determined by the value of the maximum noise level in the input video signal, i.e. the amplifier 17 should not have noise limitation when the video signal with the worst signal-to-noise ratio is fed to the device input. This noise level will be when playing for example, a third copy of the videogram. This noise level is recorded as onofiHoro voltage at the inputs of the first 23 and second 24 comparators using a peak detector 20 and an inverter 22. The signal generated by the amplifier 17 goes to the level shifter 18. All three outputs of this block have almost equal transfer coefficients for alternating components. The differences in output signals are in the presence of a constant component. At the first output connected to the input of the delay element 19, a signal is generated that is practically identical to the output signal of the amplifier 17 with the zero level of the constant component, at the second output connected to the second input of the first comparator 23, the same signal is generated, but with offset, i.e. has a constant constituting a certain sign. At the third output of the level shifting unit 18, the same signal is generated.

that at the first output, but having a constant component of opposite sign relative to the signal coming from the second output of the level shifting unit 18, the signal from the first output of the level shifting unit 18 is fed to the input of the delay element 19. The signal delay should not be less than the signal propagation delay time in both comparators 23 and 24, the OR element 25 n in the key 21. In the case of the VCR playback channel in the measurement mode or setting, the test signal from the television signal is supplied to its input. Therefore, the level of noise in the output signal of amplifier 17 can be neglected. At the same time, the output of the peak detector 20, which detects the peak value of the noise in the input video signal, sets a voltage close to zero. Consequently, at the second input of the first comparator 23, a bias voltage generated in the level shifting unit 18 with the differentiated signal imposed on it is established relative to the first input. I The magnitude of this bias voltage determines the sensitivity of the generator 7 control pulses and the entire device to the details of the image with low brightness. If there is a difference in the luminance signal in the input video signal at the output of the ush tel 17, a short pulse is generated, which, having received a constant voltage offset in the level shifting unit 18, arrives at the second input of the first comparator 23 and when it exceeds the zero control supplied to its first an input (in case of operation of the device from the sensor of a television test signal), a comparator produces a pulse whose duration is close to the pulse duration at the output of the amplifier 17, as well as the duration of the signal drop Luminance in the input video signal. Since the inputs of the second comparator 24 are turned on in reverse order with respect to the inputs of the first comparator 23 and, in addition, a differentiated signal is output from the output of the level shifter unit 18 with an offset having a reverse sign relative to the signal supplied to the second input of the first comparator 23, the second KONfflapaTop 24 is sensitive to the differences of the differentiated signal of reverse polarity relative to the signal arriving at the second input of the first comparator 23. The output signals of both comparators go to the two inputs of the element OR 25, in which they are combined into a sequence of pulses. The key 21 is switched by this series and fflys, connecting to the common bus the output of the delay element 19 for a time equal to the pulse duration, thereby translating the delay element 19 into a short-circuited mode on the output line. In the output signal of this delay line, all pulses corresponding to the signal drops in brightness in the input video signal are alternated; only the noise of the input signal remains. The presence of delay element 1, whose delay time is specified, ensures that the leading edge of the pulse, including key 21, is ahead of the pulse signal coming from the output of element 19, thereby effectively suppressing the front and most of the pulse signal at the output of delay element 19. If the delay time of the delay element 19 is shorter than the duration of the pulse including the switch 21, then in a short-circuit mm mm, also effectively suppresses the cutoff of the pulse, the post Payuschie the output of this element due to the propagation time mode short circuit, to the input of the delay line on the output side, and then after eye Chaney pulse effect in the opposite direction (from the input line to its output). Thus, at the output of the delay element 19 in the presence of a pgum in the input television signal, i.e. when the device is in playback mode, only one noise is provided, the level of which is linearly related to the noise level in the input video signal, with the signal cut to zero level in places where there are differences in the luminance signal in the input video signal. When: a hachi of such a signal at the input of the peak detector 20, a constant voltage is formed at its output, approximately equal to the peak value of the noise at its input. This voltage, coming as a reference to the first input of the first comparator 23, and inverted to the second input of the second comparator 24, makes it possible to record, in the form of output pulses of these KOM - J parators, much higher than the noise level of the differentiated signal of the input signal to the other inputs of the comparators, i.e. allows to fix availability. difference in luminance signal, if its value exceeds the noise level, i.e. if this density difference does not drown in noise The output syses of both KOfmapaTopoB, united in the element OR 25, also arrive at the input of the driver 26 pulses. In the former 26, the front of a pulse arriving at its input is practically not delayed. The axle pulse is stretched (it is only due to a delay in the cutoff of the pulse. For the duration of this pulse, key 12 is turned on in the first controlled adder 3 and a key similar to it in the second controlled adder 6, forming a linear frequency response of the device in the 0-6 band, 5 mHz. In the interval between the pulses, coming from the output ci of the generator 7 control pulses, the device transmits to the output a signal whose luminance spectrum is placed in a band approximately equal to 0-0.7 MHz, while providing a band for the chrominance signal Approximately equal to twice the value of the band for the luminance signal. Thus, the device is a fast-response frequency response linear (if there is a signal at the input, for which undistorted transmission requires a wide band) and non-linear with a band of 0.60, 8 MHz with a luminance signal and with a subcarrier band i of 0.5-0.7 mHz with a chroma signal sufficient for undistorted transmission of a signal whose spectrum is placed in this band, thereby providing an improvement in the signal-to-noise ratio in the output view osignale, improving image quality on plots with constant

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or slowly varying brightness. It does not have distortions in the color channel. At the same time, this device of the type of sensitivity and noise in places is switched to a different level of noise. The full color television input video signal has no original signal, which favorably distinguishes it

Causal type difference in delay, 5 from the prototype.

Claims (3)

1. DEVICE FOR NOISE SUPPRESSION IN THE VIDEO MAGNETOPHONE PLAYBACK CHARACTER, comprising a control pulse generator, the input of which is a video signal input, characterized in that, in order to increase the signal-to-noise ratio, the first and second delay lines are connected in series, the first controlled adder, buffer amplifier and the second controlled adder, and also introduced a third delay line, the input of which is connected to the second output of the buffer amplifier, and the output is connected to the second input of the second controlled adder, it second input of the first managed adder connected to the output of the first delay line and the control inputs of the first and second controllable adders are connected to the output of the generator of control pulses. SU "., 1124451 2. The device according to π. 1, wherein each controlled adder contains first, second, and third inverters, an emitter follower, a key, first and second current generators, the inputs of the first inverter and emitter follower combined and are the first input of the controlled adder, the input of the second and the first input of the third inverters are combined and are the second input of the controlled adder, the outputs of the first, second and third inverters are combined and are the output of the controlled adder, the output of the first current generator is connected to the power input I ^ mitternogo repeater second generator current output is connected to the control input of the third inverter between the output of the emitter follower and the second input of the third inverter is enabled key yn equals the input of which is managed control input of the adder. 3. The device according to π. 1, characterized in that the control pulse generator contains · series-connected filter plug, differentiation unit, amplifier. a level shifter, a delay element, a peak detector, a first comparator, an OR element, and a pulse shaper connected in series between the output of the peak detector and the second input of the OR element, an inverter and a second comparator, as well as a key connected between the output of the delay element and the common bus moreover, the control input of the key is connected to the output of the OR element, the second and third outputs of the level shift unit are connected to the second inputs of the first and second comparators, respectively, the input of the filter plug is the input of the control generator yayuschih pulses and an output pulse generator - the generator output. control pulses.