JPH02220568A - Video signal processing device - Google Patents

Abstract

PURPOSE:To obtain a feedback type noise reducer with small circuit constitution and less adjustment positions by applying amplitude limit to a difference component between an input signal and a 1H delay signal properly, attenuating the amplitude properly and feeding back the result to a common input signal. CONSTITUTION:A luminance signal 9 in a color video signal is applied to an input terminal 1. The signal 9 is outputted from a noise feedback circuit 2 as a signal 10 whose S/N is improved. On the other hand, the signal 11 is a signal before 1H subject to similar processing. The two signals are subtracted together by a subtractor 3 to extract a signal 12 having a frequency near (n+1/2) fH in which a color signal exists substantially. Then the signal 12 is inputted to a BPF 4, from which a signal 13 whose hand is limited to the color signal band is obtained. The signal 13 is given to a limiter 5, in which the amplitude is limited and from which the signal 14 is obtained. Succeedingly, a signal 15 resulting from the signal 14 attenuated by a 1/2 divider 6 is subtracted from the signal 11 by a subtractor 7 and a final output signal 16 is obtained from an output terminal 8. Thus, a residual color signal and a mixed color signal whose level is inverted for each line are eliminated. The effect is realized by one delay device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video signal processing device, and particularly relates to a suitable video signal processing device for reducing noise in a luminance signal. 3. [Prior Art] A conventional device includes: As described in pages 140 to 146 of Broadcasting Technology, January issue of Showabe, S/N improvement using a noise reducer and removal of residual and mixed color signals in luminance signals using a comb filter are each performed using separate circuits. It was done.

[Problem that the invention seeks to solve]

In the above-mentioned conventional technology, a plurality of delay means are required, which increases the circuit scale, and there are problems in terms of cost and productivity, such as an increase in the number of adjustment points for adjusting the delay time.

Further, there is a problem in that no consideration is given to the frequency band, amplitude level, etc. that are affected by the comb filter processing, which leads to deterioration of the resolution in the vertical direction of the screen.

An object of the present invention is to provide S
/N improvement, removal of residual and mixed color signals in the high frequency region, and removal of contour noise, which is noise in the high frequency region, without causing vertical resolution deterioration.
The object of the present invention is to provide a feedback type noise reducer that processes simultaneously using one delay device, has a small circuit configuration, and has fewer adjustment points.

[Means for solving problems]

The above object can be achieved by constructing a 1H4 feedback type 0 noise reducer as described below.

That is, the amplitude of the difference component between the human input signal and the 1H delayed signal is appropriately limited, and after being further reduced as appropriate, it is fed back to the common input signal. The input signal subjected to feedback is input to a 1H delay device and used to generate a feedback signal for the next line. here,
The difference between the input and output signals of this 1H delay device is determined, and the difference signal is limited to the band of the color signal from the BPFJ. Furthermore, after limiting the amplitude of the BPF output signal, 1H
The signal obtained by addition or subtraction with the input or output signal of the delay device is defined as an output signal.

[Effect]

According to the above means 1, if the attenuation amount of the feedback signal of the feedback circuit in the first half is k (0≦≦1), then the gain is nfH (n is a non-negative integer, fB is the frequency of the horizontal synchronizing signal) 1 is 0 (dBl, gain at (n + −) fz is 10
It exhibits a frequency characteristic of log(1-k)/(1+k)) (dB) and attenuates noise components existing around (n+-)fH. Also, this feedback signal is amplitude limited by an appropriate amount, so if there is no correlation between lines,
In other words, when the difference component between the input signal and the 1H delayed signal has a large amplitude, the amount of feedback is limited and no deterioration of vertical resolution occurs.

On the other hand, if we take the difference between the input and output of the 1H delay device, we get (n
+-) It exhibits a frequency characteristic in which the gain is OdB at the frequency of fII and the gain is infinitesimal at the frequency of nfH, and after limiting the signal to the color signal band with a BPF, it is added or added from the input or output of the 1H delay device. Since it is subtracted, only the gain of the color signal band (n + 2) fl is infinitesimal and nfH is 0
(dB). Also, in this case, the amplitude of the BPF output signal is limited, so if there is no correlation between lines, that is, if the difference signal has a large loss width, the frequency characteristics described above will not occur, and the frequency characteristics will be flat. , and no vertical resolution deterioration occurs.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. First, the configuration and operation of this embodiment will be explained.

The luminance signal in the color video signal is applied to the input terminal l# as the input signal 9. The signal 9 is set to S by the noise hot water speed circuit 2.
/N is output as an improved signal 10. On the other hand, signal 11 is a signal 1H ago that has undergone similar processing. This 2
The two signals are subtracted by the subtractor 3 to extract the signal of the (n''2) tH leg peripheral frequency where the color signal originally exists.Next, the output signal 12 is filtered by the BPF 41, and the color (
A signal 13 is obtained which is limited to i upper bands. The amplitude of the signal 13 is further limited by a limiter 5 to obtain a signal 14. Then, in order to adjust the gain of the signal 14, the signal 15 attenuated by the 1/2 multiplier 6 and the signal 11 are subtracted.
The final output 48 No. 16 is obtained at the output terminal 8. This makes it possible to remove residual color signals that are inverted line by line and mixed color signals. Here, since the 172 multiplier 6 for gain adjustment may be included when configuring the BPF 4 and the limiter 5, it is not necessarily necessary. Also, subtractor 3
If the polarity of is reversed, the same processing will be performed if the processing in the subtracter 7 is addition.

Next, the processing of the noise feedback circuit 2 will be explained in more detail with reference to FIG. Since there is not necessarily one type of configuration of a noise feedback type circuit, an example of the configuration is (al,
(b) Explain in two ways. (In al, the subtracter 20 calculates the difference 1/22 between the input signal 1 and the signal 11 obtained by delaying the output signal 10 by 1H:M delaying device 21 by 1H. This signal 22 is limited in width by the limiter 19. In other words, the signal that has not been subjected to the noise restriction by this limiter is regarded as noise.Furthermore, the signal n is attenuated by the multiplier 18 (o≦≦1) to obtain the signal 24.
This signal is fed back to the input signal l by an adder 17 to obtain an output signal 10. Also, in (bl), a signal part is obtained by attenuating the input signal 1 by the (1-k) multiplier 25. On the other hand, a signal 29 is obtained by attenuating the signal 11 whose output is delayed by 1H by the multiplier 18. The feedback output signal 10 is obtained by adding the two signal parts and 4. However, in the case of
-k) and a correlation detector 26 for determining the magnitude of the amplitude of the difference signal 22 in order to obtain a signal 27 for controlling the multiplier k. The limiter in (a) substitutes the dynamic characteristics of this correlation detector.

Next, a specific example of the characteristics of the limiter 19 will be shown using FIG. In general, limiter characteristics used in analog signal processing have input/output characteristics as shown in FIG.

In this way, by linearly passing only input signals with small signal amplitudes, it has the characteristic of passing only small differences between lines. However, since a fixed value is output for a large difference, the output signal 10 will be slightly degraded, but the vertical resolution degradation can be prevented to a sufficient degree visually. On the other hand, in analog signal processing, it is said to be relatively far apart, but in digital signal processing, it can be easily configured (bl, !01 characteristic, the output signal amplitude starts to attenuate from a specific input amplitude value of 30,
At a specific input amplitude value of 2 or more, it has an infinite amount of attenuation, that is, a cutoff characteristic. This makes it possible to completely suppress vertical resolution blur. The same can be said of the limiter 19 as well. Moreover, FIG. IA7 is another configuration diagram of this embodiment. In this configuration, the subtracter 3 shown in FIG. 1 and the subtracter 20 shown in FIG. 2 are used in common. Furthermore, a multiplier is added after the BPF 4° limiter 5, but this is to control the amount of S/N improvement in the high frequency range, and it can also be adopted in the embodiment shown in Figure 1. be. In other words, the more the output signal of the limiter 5 is attenuated by the multiplier, the less the component of the signal averaged between the lines is included in the output signal.

The effects of this example will be summarized below. First, it is possible to construct a feedback noise reducer that can make the gain infinitely small only in the color signal band at the frequency of (n+7)fz. As described above, the S/N improvement effect of the luminance signal and the removal of residual components of the chrominance signal can be simultaneously achieved with one delay device. Second, although any of the above-mentioned characteristics of the limiter can be used to achieve sufficient effects, by using a limiter that has the characteristic of blocking the large intestine import force, the deterioration of vertical resolution can be completely prevented. can be suppressed.

Third, by setting the limiter level 81 of the limiter 19 higher than the limiter level 81 of the limiter 5, it is possible to configure the noise reducer 8 with emphasis on the S/N improvement effect in the low frequency region. can. Conversely, by setting the limiter level 81 of the limiter 19 lower than the limiter level 81 of the limiter 5, the cross color reduction when adding luminance color signals by the comb filter can be reduced.
It is possible to have a configuration in which the

Next, a second embodiment of the present invention will be described with reference to FIG.

This embodiment basically has the configuration shown in FIG. 1, and the configuration shown in FIG.
Al, and switches are provided to realize various other modes. The configuration and operation will be described below in order.

The input signal 9 applied to the input terminal 9 is processed by the noise feedback circuit 2 to obtain the output signal 10 as described above. Signal 10 and signal 9 are selected by switch 32 and output as signal 39. Switch 32 is controlled by an external control signal, and when it is desired to cancel the processing of the noise feedback circuit, signal 9 is selected. .Signal 39
is input to a subtracter 3 for realizing enhanced noise removal in the color signal band.

Further, the signal 39 and the delayed signal 11 are selected by the switch 33 and outputted as the signal 76. Signal 76 is 1H
The signal is input to the delay device 21. Switch 2 receives control signal 42
It is controlled by This is to select signal 11 when cycling through and compensating for delayed signals when the input signal is destroyed or missing. The processing until the output signal 12 of subtraction g-3 reaches the subtracter 7 is the same as that of the first embodiment described above.
is the same as As the other signal input to the subtracter 7, the delayed signal 11 and the signal 39 are selected by the switch 35 and input as the output signal I. This switch is controlled by the control signal 41, but if the input signal is missing or destroyed, the above-mentioned interpolation mode takes priority, so the control fixed circuit 34 changes the control signal to the control signal 42. It is controlled by a dependent signal 43. That is, if input signal 9 is invalid, switch 36 selects signal 11, otherwise signal 39 is valid. For the signal material, select signal 11 if you want the delay time of the output luminance signal to be a signal delayed from 1H, and select signal 39 if you want to use it as the current signal.

The signal material is input to the subtracter 7, and only the color signal band is S/N
A signal 16 with an enhanced improvement effect is output. Furthermore, signal 1
6 and the signal material are selected by switch 36. This means that when it is desired to cancel the S/N improvement enhancement of the color signal band using the control signal 40, the signal I is selected. However, when the input signal is invalid, the interpolation mode takes priority and the signal 40 is fixed to the selected state of the signal I by the control fixing circuit 37. As described above, the final output signal 46
is output to terminal 8.

Next, we will summarize the characteristic effects of this embodiment.

First, controlling switch 32 and switch 36
From this, there is a feedback noise reducer mode that enhances the amount of S/N improvement in the color signal band, a feedback noise reducer mode that has the same S/N improvement effect in all bands, and a mode signal that operates as a <C type filter. It is possible to configure four modes, including a mode in which no processing is performed. This allows selection of optimal processing for various input signal numbers. That is, when this embodiment is applied to a magnetic recording/reproducing apparatus as described later, noise feedback for improving the low-frequency S/N is unnecessary in a recording/reproducing mode with a good low-frequency S/N.

In addition, in the case of a method that records and reproduces only the band from 0 to 3.2 MHz, in the case of a black and white signal, or in a method that outputs luminance and color separation, the S/N in the color signal band is
Improvement and reinforcement may be ineffective or unnecessary.

As described above, the S/N improvement mode is designed to accommodate various types of crowds. Second, if there is a drop in the input signal, it can be compensated for by using the 1H delay device of this embodiment. Thirdly, the 1H delay mode and non-delay mode of the luminance signal can now be selected. This makes it possible to apply the present embodiment to a magnetic recording/reproducing apparatus as described later and correct the center of gravity shift between the luminance signal and the color signal when dubbing editing is performed using the present embodiment.

Finally, an embodiment in which the present invention is applied to a magnetic recording/reproducing device will be described with reference to FIG.

FIG. 6 is a diagram showing a case where the above-mentioned second embodiment is applied to a reproducing system of a magnetic recording/reproducing apparatus. Its configuration and operation will be explained below.

A signal B is obtained by reading the signal recorded on the magnetic tape 47 by converting it into a magnetic head for reproduction. The signal ω is amplified by a reproducing amplifier 49 to obtain a signal B. Signal 6 is FM in the high range
Since it is a mixed signal of a modulated luminance signal and a color signal that has been converted into a low frequency signal, a high frequency TA wave circuit (hereinafter referred to as HPF) 50 and a low frequency leakage circuit (hereinafter referred to as LPF) 51 generate a signal 6, respectively.
5 and signal 70. The signal 65 is amplified by a limiter amplifier for correcting output changes in the amplitude direction by an FM signal limiter. Between the output signals is an FM demodulator 8
is input to. The output signal 67 is processed by an LPF 55 to remove carrier signals left in the high frequency range to obtain a signal part. This signal portion is digitized by an analog-to-digital converter 56 and is input into the system 57 of the second embodiment described above. At this time, D.O.C.
The system 57 output signal 46 is converted into an analog signal 69 again by a digital-to-analog converter. The color signal is restored to the original frequency and added to the color signal in the adder 61.The color signal is frequency-converted in the color signal processing circuit 59 because the signal 70 remains low-frequency converted. The color signal is processed by BPF6 to remove signals outside the band.
The output signal 73 of the adder 61, which is processed at 0 and then added to the luminance signal as a signal 72, is amplified by an output amplifier and then outputted to a terminal 75 as a signal 74.

The characteristic effects of this embodiment will be described below.

@1 According to the present invention, dropout compensation is possible without having an additional 1H delay device.

No. 2, we aim to reduce reproduction noise in the low frequency range, which is unique to magnetic recording and reproducing devices as shown in Fig. 4, and to reduce contour noise, which is noise in the high frequency range, and in particular,
It is possible to effectively remove residual color signals in a recording device after separating color signals and mixed color signals during reproduction. Thirdly, the present invention itself does not necessarily need to be applied to a magnetic recording/reproducing device after being digitized. However, delays using glass delay lines and COD, which have been conventionally used for analog signal processing, have insufficient bandwidth and temperature characteristics, and when realizing the shared use of delay lines as described above, it is difficult to match the delay times. There is a need to do. These problems require a large number of adjustment points when configuring the system, which can be said to be an inconvenience to productivity and a large burden in terms of cost. On the other hand, with digital signal processing, there is almost no need to adjust the band, temperature f: characteristics, and delay time adjustment is also easy. In particular, with the advent of 5-VH8 and the like, there is a need to be able to set various modes in the reproduction system in a situation where various types of comb filter processing are performed in the recording system.

Furthermore, in order to construct such a system at a low cost, it is impossible to use a dual-purpose delay device. As described above, this example has the effect of being able to cope with diversified luminance signal and chrominance signal separation methods without increasing the circuit scale and without increasing the number of adjustment items.

〔Effect of the invention〕

According to the present invention, the gain is 0 (dB) (n
+2) At a frequency of 1Jr, the gain is 10 log((
1-k)/(1+k)) (dB), while the gain can be increased infinitely by (n + 2) III, especially in a band where color signals coexist. As a result of the above, S/N improvement in low frequency areas such as horizontal noise, reduction of cross colors that occur when adding luminance signals and color signals from residual and mixed color signals, and contour lines that appear vertically on the screen can be improved. This has the effect of improving the S/N in the high frequency region, which appears to be in a jagged state.

Furthermore, in the present invention, since the above-mentioned improvement effect is limited to only the portion where the inter-line correlation is strong, there is no fear of vertical resolution deterioration.

Furthermore, the present invention has the effect that the above effects can be realized simultaneously by one delay device, and the circuit scale can be made smaller than that of the conventional one.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first MfA example of the present invention,
Figure 2 is a block diagram showing an example of the configuration of a noise feedback circuit, I
@Figure 3 is a diagram showing an example of the characteristics of limiters 2 and 1, Figure 4 is a diagram showing the noise distribution in the reproduced luminance signal of the magnetic recording and reproducing device, and Figure 5 is a block diagram showing the second embodiment of the present invention. figure,
FIG. 6 is a block diagram showing an embodiment in which the second embodiment is further applied to a reproducing system of a magnetic recording/reproducing apparatus, and FIG. 7 is a block diagram showing another configuration of FIG. 1. 2...Noise feedback circuit 3...Subtractor 4...Band bus filter (BPF) 5...Limiter
7...Subtractor 18...k multiplier 1
9...Limiter 21...1H delay device 32.
...Switch...Switch 34...Control fixed circuit A...Switch 36...Switch 37...Control fixed circuit 8...FM signal demodulator 56...Analog-digital converter 57・・・
・Return noise reducer enclosure...Digital-to-analog converter 61...Luminance color signal adder Kabuto 1 diagram (good) (C) Closed 4 diagrams Kabuto r7 Suihe I person noise +i5 mej- Noise d

Claims (1)

[Scope of Claims] 1. A means for inputting a luminance signal in a video signal as a first signal and outputting it as a third signal, the means comprising: When the difference component is minute, the mixing ratio of the third signal to the first signal becomes larger, and the first signal and the third signal are added to obtain a second signal, and the second signal is scanned one horizontal scan. a first means for obtaining a third signal by delaying a period (hereinafter 1H); a second means for obtaining a fourth signal which is a difference component between the second signal and the third signal; a third means for obtaining a fifth signal band-limited by a wave circuit (hereinafter referred to as BPF); a fourth means for obtaining a sixth signal with the amplitude of the fifth signal limited; When the second signal is subtracted from the third signal, the sixth signal is subtracted from the third signal, or when the polarity of the subtraction in the second means is reversed, the third signal and the sixth signal are added. A video signal processing device comprising: fifth means for obtaining a seventh signal as an output. 2. A sixth means for obtaining a final output eighth signal by switching the output second signal and the output seventh signal of the first means, and switching the input second signal and first signal to the second means; a seventh means for obtaining a new input ninth signal to the second means;
2. The video signal processing device according to claim 1, wherein the video signal processing device is controllable by a signal. 3. Eighth means for switching the delayed output third signal of the first means with the seventh signal to obtain a new final output, the twelfth signal; 2. The apparatus according to claim 1, further comprising a ninth means for switching with a second signal as an input signal of the means, the eighth means and the ninth means being controllable by a thirteenth signal from outside. Video signal processing device. 4. In place of the fifth means, a tenth means for processing the sixth signal and the second signal by an operation inverse to that of the fifth means is provided, or a fourteenth means which is the output of the tenth means is provided. 2. The video signal processing apparatus according to claim 1, further comprising eleventh means for outputting the signal by switching it with the seventh signal. 5. The fourth means is that the attenuation amount of the amplitude limit is the first of the input amplitudes.
2. The video signal processing device according to claim 1, wherein the video signal processing device has a characteristic that becomes further larger from a specific value or more, and becomes infinite, that is, a cutoff characteristic when the second specific value or more exceeds the second specific value. 6. F in a luminance signal reproducing system of a magnetic recording and reproducing device performing low gamut color conversion processing in the video signal processing device of claim 1;
A video signal processing device characterized in that it is arranged after an M demodulator and before an adder for adding reproduced color signals. 7. It is characterized by comprising a twelfth means for digitizing the input first signal and a thirteenth means for analogizing the output seventh signal, and using a digital memory as the 1H delay means in the first means. The video signal processing device according to claim 7.