JPS6116068A - Video signal processor - Google Patents

Abstract

PURPOSE:To reduce the noise level and also to correct the frequency with no deterioration in signals together with the full semiconductor, formation by pressing or emphasizing the normal band component of a filter which transmits a digital luminance signal in response to the amplitude of the input signal of a following nonlinear processing circuit. CONSTITUTION:A digital luminance signal is supplied to an input terminal 17 and then to an adder circuit 23 as well as a filter 18. This filter 18 is equal to an HPF consisting of a delay circuit 19 having delay time D, a subtractor circuit 20 and a coefficient unit 21. The component passed through the filter 18 is supplied to a nonlinear processing circuit 22. The circuit 22 presses or emphasizes the pass band component of the filter 18 according to the amplitude of the input signal. The output of the circuit 22 is supplied to the circuit 23, and the processed signal is outputted to an output terminal 24. Thus a circuit is produced through the full semiconductor formation. This can reduce the noise level and correct the frequency with no deterioration in signals.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention is a videotape recorder [hereinafter referred to as +IV1-R]
6, which relates to a video signal processing device that can be used for applications such as the following.

Conventional configurations and their problems In recent years, civil a that has been widely used: JI V T
In 'R, the luminance signal is FM modulated and recorded on a 10K tape. This brightness (iE is re-[
system, and the original luminance signal is reproduced. However, since the frequency characteristics and S/N ratio of the tape head system are not necessarily sufficient, the reproduced luminance signal is a noisy signal with degraded midrange to high range. Therefore, a frequency correction circuit that corrects the frequency characteristics of the reproduced signal, a noise canceller that suppresses noise, and the like are used.

A conventional frequency correction circuit and noise chiton cellar will be explained below.

Figure 1A is a circuit diagram of a conventional frequency correction circuit, where 1 is an input terminal for the reproduced and demodulated luminance signal, 2 is a transistor for No. 48 amplification, 3 is a resistor with a resistance value R, and 4 is a passive element. In the configured impedance, the impedance value of this impedance 4 is Z. 5 is an output terminal for a frequency-corrected signal. Here, an example of the configuration of the impedance 4 is not shown in FIG. 1B. 6, 7.9 is resistance, 8.1
0 is a capacitor, and 11 is a coil.

Next, the operation will be explained. The circuit shown in FIG. 1A is a J-mitter grounded amplifier circuit, and the transfer function of a signal from input terminal 1 to output terminal 5 is approximately expressed by R/Z.

Therefore, by appropriately selecting the values of the passive elements 6 to 11 shown in FIG. 1B, the frequency characteristic f1 of the transfer function as shown in FIG. 1C can be obtained. by the way. Assuming that the spectrum of the luminance signal recorded on a VTR is as shown in FIG. 2a, the yli signal after being reproduced and demodulated becomes a signal with degraded high frequencies as shown in FIG. Also here, 13
What is indicated by one line is the noise component mixed in from recording to reproduction and demodulation. By inputting the signal whose high frequency region has been degraded in this way to a frequency correction circuit having the frequency characteristics shown in FIG. 1C, it is possible to improve the frequency characteristics shown in FIG. 2C.

However, in the above configuration, as shown by diagonal lines in FIG. 2C, noise components mixed into the signal are also emphasized at the same time, resulting in an image with a lot of noise.

Conventionally, therefore, devices called noise chiton cellers have been used to reduce noise. A conventional noise canceller will be explained below. FIG. 3A is a circuit block diagram of a conventional noise canceller, where 12 is an input terminal of an analog luminance signal J, 13 is a Hanoi filter,
As this filter 13, a bypass filter is generally used. A limiter 14 limits the amplitude of the output signal from the filter 13.

15 is an arithmetic unit that subtracts the output signal of the limiter 14 from the input signal from the input terminal 12; 16 is an output terminal for a signal with suppressed noise.

Next, the operation will be explained. When a luminance signal with a spectrum as shown in FIG. 2C is input to the input terminal 12, the filter 1
A high frequency signal mixed with noise appears at the output of the filter 13. The output signal of the filter 13 is then supplied to a limiter 14. The limiter 14 has input/output characteristics as shown in FIG.
By subtracting the luminance signal from the original input signal at the output terminal 16, a noise-reduced luminance signal can be obtained.

However, the conventional frequency correction circuit and noise canceller described above have several drawbacks.

First of all, in the frequency correction circuit, together with the signal:
It would be unreasonable to emphasize the noise and subsequently suppress the emphasized noise using a noise canceller, which would require a large number of circuit parts and complicate the configuration of the VTR. Second, in the frequency correction circuit, the delay time of the signal from input to output changes depending on the frequency, resulting in an unnatural image. Thirdly, since the limiter in the noise canceller is constructed using semiconductor nonlinear elements such as DA and IMADE, the third
The input/output characteristics must be as shown in Figure B! ? First, even when the input signal is large, the output signal does not become O, and the resolution of the image inevitably deteriorates. , Furthermore, in the filter 13 of the noise canceller (11y delay occurs in the t1 signal, the delay time of the Gl+ signal output from the output terminal 1G changes depending on the level of the signal 3 passing through the limiter 14,
It has many problems, such as deterioration of image quality.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned drawbacks of the conventional technology, thereby making it possible to simplify and reduce costs by using all semiconductors, as well as exhibiting the effect of eliminating chords that cause signal deterioration and r<lfi. Another object of the present invention is to provide a video signal processing device that can correct the frequency characteristics of a signal without emphasizing noise.

Structure of the Invention In order to achieve the above object, the video signal processing device of the present invention includes a filter that passes a specific frequency band of an input luminance signal obtained by digitizing the luminance signal, and a nonlinear processing that nonlinearly processes the signal that has passed through this filter. and an arithmetic circuit that mixes the input luminance signal or a signal obtained by delaying the input luminance signal by a predetermined period and the output signal of the nonlinear processing circuit, the signal passing through the filter depending on the amplitude of the input signal of the nonlinear processing circuit. This configuration is such that band components are suppressed or emphasized.

According to this configuration, by performing processing in the form of a digital signal, it is possible to exhibit an excellent noise removal effect without degrading the signal, and at the same time, to perform frequency correction of the signal without emphasizing the noise.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below based on the drawings.

FIG. 4 is a circuit block diagram of a 113-channel image processing device according to the first embodiment of the present invention, in which 17 is an input terminal for a digitized luminance signal, and 18 is a filter.

This filter 18 includes a delay circuit 19 with one delay time,
It consists of a dedicated circuit 20 and a coefficient unit 21.

22 performs nonlinear processing on the output signal of the filter 18! 23 is a summation circuit that subtracts the output transmission of the nonlinear processing circuit 22 and the human input luminance signal, and 24 is an output terminal that outputs the processed signal (1).

Next, the operation will be explained. First, the basic operation of this embodiment will be explained. The frequency characteristics of the filter 18 are, for example, a delay time of 140 nsec, a fifth
As shown in the figure, it has a high-pass type characteristic, and the input terminal 11
The high-frequency components of the luminance signal inputted to the luminance signal are passed through and supplied to the nonlinear processing circuit 22. Now, if the input/output characteristics of the nonlinear processing circuit 22 are as shown by the solid line in FIG. 6a, then
The signal input to the input terminal 17 appears as it is at the output terminal 24 in FIG. 4, and the frequency characteristic of the system from the input terminal 17 to the output terminal 24 is as shown by the solid line H in FIG. On the other hand, the input/output characteristics of the nonlinear processing circuit 22 are shown in FIG.
When the frequency characteristic of the system is as shown by the solid line -r in FIG. Conversely, when the input/output characteristics of the nonlinear processing circuit 22 are as shown by the solid line E in FIG. 6A, the frequency characteristics of the system are such as to emphasize high frequencies, as shown by the solid line N in FIG. 6A. Similarly, if the input/output characteristics are as shown by the solid line in Figure 6a,
The frequency characteristics of the system are as shown by the solid lines T and R in Figure 6, respectively.

The following is the basic operation of this embodiment.

Now, suppose that a reproduced luminance signal containing degraded noise in the high frequency range is input to the input terminal 17 as shown in FIG. be done. Here, since a luminance signal generally has many low-frequency signal components, when the amplitude of the extracted high-frequency component is small, it can be regarded as almost noise.

Therefore, if the input/output characteristics of the nonlinear processing circuit 22 are shifted as shown in FIG. 7a, if the high frequency component obtained by the filter 18 in FIG. The characteristics are as shown by the solid line in Figure 6, and high-frequency noise can be suppressed, and if the high-frequency component obtained by the filter 18 is large and is regarded as a signal, the frequency of the device will change. The characteristics are as shown by the solid line H in Figure 6, and the signal does not deteriorate. but,
In the nonlinear characteristic shown in FIG. 7a, the output does not become O even if the input is sufficiently large, so the resolution deteriorates to some extent. Therefore, it is also possible to make the nonlinear characteristics as shown in FIG. This does not degrade the resolution of -U fj. However, since this characteristic is discontinuous at the threshold portion, unnatural disturbances may occur at this discontinuous portion due to the sensitivity of small values.

In this case, it can be improved by adopting a characteristic without discontinuities as shown in FIG. 7C. As described above, by appropriately setting the nonlinear characteristics, noise can be suppressed without deteriorating the (a).On the other hand, it is also possible to set the nonlinear input/output characteristics as shown in Figure 7d. It is.

In this case, when the amplitude of the signal passing through the filter 18 is large and can be regarded as a signal, the frequency characteristic of the device becomes a characteristic that emphasizes the high frequency range, as shown by the solid line N in FIG.

Further, when the amplitude of the signal passing through the filter 18 is small and can be considered as noise, the frequency characteristic of the device becomes as shown by the solid line H in FIG. 6, and the noise is not emphasized. Therefore, for a signal with degraded high frequencies as shown in FIG. 2, the frequency characteristics can be corrected only for the signal components without emphasizing the noise. Note that by using the nonlinear characteristic shown in FIG. 7e, the effect of frequency correction can be further increased for signals with relatively small signal amplitudes.
Moreover, if the characteristic is shifted to the characteristic shown in FIG. 7f, the adverse effects caused by discontinuity can be eliminated. Furthermore, it is also possible to make the nonlinear characteristics as shown in FIG. 7g. In this case, as can be inferred from the previous explanation, the noise can be reduced to 1 in Figure 6.
This is suppressed by the frequency characteristic indicated by the solid line shown in FIG.

By the way, the configuration of the nonlinear processing circuit 22 having 41 different linear input/output characteristics as shown in FIG. 7 can be made into many configurations by suitably combining logic circuits according to the respective characteristics. Read-only memory (hereinafter referred to as rR)
By using OMJ (also known as 1J), various nonlinear characteristics can be realized in the cabinet 11. In other words, the input signal of the nonlinear processing circuit 22 is used as an address, and the memory content corresponding to the address is used as an output signal.

This makes it possible to easily realize arbitrary input/output characteristics.

As described above, according to this embodiment, since processing is performed in the form of a digital signal, the input/output characteristics of the nonlinear processing circuit 22 can be set arbitrarily, and this can be easily realized especially by using a ROM. This suppresses noise without degrading the signal (1): characteristics that correct the frequency characteristics of the signal without emphasizing the dI sound, and further suppress noise and improve the frequency characteristics of the signal. It is possible to easily realize even the characteristic of correcting the noise, and it is possible to simultaneously realize the conventional frequency correction circuit and the noise correction circuit with one configuration. In addition, since the rebate processing is performed in the form of a digital signal, 1
Since it can be configured on a deep semiconductor and does not require external components, it is possible to miniaturize the device and reduce costs.
It has the following advantages.

In the above embodiment, the nonlinear processing circuit 22 has one nonlinear input/output characteristic, but it is also possible to have a plurality of nonlinear input/output characteristics, and to select and use one of them as appropriate. This will be explained using FIG. 2
9 is a nonlinear processing circuit, and 27 and 28 are an input terminal and an output terminal of the nonlinear processing circuit 29, respectively. The very linear processing circuit 29 also includes nonlinear input/output circuits 30a to 3On, each having different nonlinear input/output characteristics, and switches 31a to 3On for selecting these nonlinear input/output circuits 30a to 300.
31b, and the switches 31a and 31b are controlled by the control 1 signal. This nonlinear processing circuit 29
This can be easily realized, for example, by storing a plurality of types of input/output characteristic tables in a ROM and selecting one of them. By using such a non-linear processing circuit 29, it becomes possible to adjust the frequency correction amount, noise reduction Mftt, etc. as appropriate depending on the type of image, the SN ratio, or the user's preference.

FIG. 9 shows the second embodiment of the present invention (Lj (Jru image (
, l; 8 processing device circuit block diagram, 33G is a]r filter, and this filter 33 has a delay fKli 1fi
l D delay circuits 34a and 34b, each with a coefficient of 1
/4. It is composed of -1/2°1/4 coefficient multipliers 35a to 35C and an adder circuit 36. 37 is a delay circuit that delays the input luminance signal by Dl and supplies it to the adder circuit 23.

This second example of actual flow differs from the first example shown in FIG.
This is the insertion of In the frequency domain, the frequency characteristics of the filter 33 are the same as those of the filter 18 in FIG. 4 whose characteristics are shown in FIG.
are almost the same, and the relationship between the characteristics of the nonlinear processing circuit 22 and the system from the input terminal 17 to the output terminal 24 is also shown in FIG.
This is almost the same as the case of the first embodiment described using b. However, in the first embodiment shown in FIG. 4, the delay time from the input to the output of the filter 18 is J times greater than the frequency, and as a result, the delay time of the signal from the input terminal 17 to the output terminal 24 is This also varies depending on the frequency of the input signal and the characteristics of the nonlinear processing circuit 22, and may unnaturally deteriorate the image quality. In contrast, in this embodiment, the delay time between the input and output of the filter 33 is constant at D regardless of the signal frequency, and the delay time of the signal from the input terminal 11 to the output terminal 24 is also reduced by inserting the delay circuit 37. Since it is always D regardless of frequency or nonlinear characteristics, it has the characteristic of not deteriorating the signal. The delay circuit 37 in this embodiment can also be used as the delay circuit 34a, thereby reducing the circuit scale.

FIG. 10 is a circuit block diagram of a signal processing device according to a third embodiment of the present invention. The difference between this embodiment and the second embodiment shown in FIG. 9 is the configuration of the filter and its It's in the frequency characteristics. 38 is a filter, and this filter 38 includes delay circuits 39a to 39c with delay times of 3D, 2[), and D(7), n circuits 40a to 40c, and a coefficient unit 41 with a coefficient of 1/8. It is made up of.

The J5 delay circuit 39a also functions to delay the signal led to the adder circuit 23 by 3D without reducing the filter 38.The frequency characteristic of this filter 38 is such that the delay time is, for example, 140nsC before the delay time. When I made Shun, the 11th
As shown in the figure, it has band-pass characteristics. The characteristics of the turnout of the nonlinear processing circuit 22 are shown in FIG.
7, the frequency characteristics of the circuit from the input terminal 17 to the output terminal 24 in FIG. 10 will be as shown by the solid line Luhe-El in FIG. 12, respectively. Also at this time,
The delay time of the signal from the input to the output is always constant in 3D, regardless of the second frequency or the input/output characteristics of the nonlinear processing circuit 22. Now, if the input/output characteristics of the nonlinear processing circuit 22 are expressed as shown in FIGS. ~2M) It is possible to enhance the noise low range or the signal in the middle range around -12. In this embodiment, by making the filter a band-pass type, it is possible to reduce mid-range noise that is visually more disturbing than band noise. , j: input V 'T'
The amplitude of the reproduced luminance signal of R is generally as shown in Figure 2, and in the high range around aMHz, the amplitude is j:
Because it is difficult to distinguish between noise and noise, if a high-pass filter is used, depending on the nonlinear input/output characteristics, it may emphasize the noise or suppress the signal, resulting in deterioration of image quality. In the middle range of 1 to 2 MHz, it is easy to distinguish between a signal and noise based on amplitude, and it is possible to reduce noise or enhance a striped signal without deteriorating image quality.

DETAILED DESCRIPTION OF THE INVENTION [As mentioned above, according to the present invention, since the video signal is processed in the form of a digital signal, the entire device can be made into a semiconductor, and it is possible to make it into a single chip. , it is possible to simplify the device and reduce costs. Further, it is easy to make the signal delay time from input to output constant regardless of the signal frequency, and image quality is not degraded. Furthermore, the nonlinear input/output characteristics of the nonlinear processing circuit can be set arbitrarily, and this characteristic can be used to suppress the frequency components of the input luminance signal that pass through the filter in a range where the input signal amplitude of the full linear processing circuit is small. By adjusting the characteristics, it is possible to reduce noise without deteriorating the information (3).

In addition, by changing the nonlinear input/output characteristic to a characteristic that emphasizes the frequency component that has passed through the filter in a range where the input signal amplitude of the nonlinear processing circuit is larger than a predetermined level,
Signal frequency correction can be performed without emphasizing human noise. Furthermore, the non-linear input/output characteristics are set to suppress the frequency components that have passed through the filter in a range where the input signal is lower than a predetermined level, and to emphasize them in other ranges where the input signal amplitude is lower than a predetermined level. It is possible to suppress noise and correct the frequency of the signal. These nonlinear processing circuits can easily realize arbitrary nonlinear input/output characteristics by using +−<OM.

In addition, the nonlinear processing circuit can be easily configured to be able to select one of multiple types of input/output characteristics as appropriate. It becomes possible to adjust the amount of noise reduction and the amount of frequency correction as appropriate. Furthermore, by covering the filter with a band-pass type filter, it is possible to remove mid-range noise, which tends to visually interfere, without degrading high-frequency signals, which are difficult to distinguish based on the amplitude of noise and signals. .

[Brief explanation of the drawing]

FIG. 1A is a circuit diagram of a conventional frequency correction circuit, FIG. FIG. 3A is a circuit block diagram of a conventional noise canceller, FIG. 8 is an explanatory diagram of input/output characteristics of the same noise canceller, and FIG. 4 is a diagram of the first embodiment of the present invention. 5 is an explanatory diagram of the frequency characteristics of the filter in the video signal processing device, FIG. 6 is an explanatory diagram of the input/output characteristics of the video signal processing device, and FIG. 7 is an explanatory diagram of the input/output characteristics of the video signal processing device. An explanatory diagram of input/output characteristics of a nonlinear processing circuit in a video signal processing device, FIG. 8 is a configuration diagram of a nonlinear processing circuit having a plurality of nonlinear input/output characteristics, and FIG. 9 is a diagram showing a second embodiment of the present invention. FIG. 10 is a circuit block diagram of a video signal processing device according to the third embodiment of the present invention. FIG. 11 is a circuit block diagram of a video signal processing device according to the third embodiment of the present invention. FIG. 12 is an explanatory diagram of the frequency characteristics of the video signal processing device. 18, 33.38... Filter, 22.29... Nonlinear processing circuit, 23... Addition Practical circuit agent Hiroshi Morimoto Figure 1 Same as 10: i Figure 2 Frequency f Frequency circle i Figure 3 Figure 5 Figure 6 Same wave number Figure 7 (cl) Cb) (C) ( d)
(e＞
cln (/) Figure 8 q I

Claims (1)

[Claims] 1. A filter that passes a specific frequency band of an input luminance signal obtained by digitizing the luminance signal, a nonlinear processing circuit that nonlinearly processes the signal that has passed through this filter, and the input luminance signal or the input luminance. an arithmetic circuit that mixes a signal delayed by a predetermined period with an output signal of the nonlinear processing circuit, and a configuration in which a passband component of the filter is suppressed or emphasized according to an input signal amplitude of the nonlinear processing circuit; video signal processing equipment. 2. Claim 1, wherein the nonlinear processing circuit has an input/output characteristic that suppresses the passband components of the filter in a range where the input signal amplitude is smaller than a predetermined level.
The video signal processing device described in Section 1. 3. Claim 1, wherein the nonlinear processing circuit has an input/output characteristic that emphasizes the passband components of the filter in a range where the input signal amplitude is larger than a predetermined level.
3. The video signal processing device according to item 1 or 2. 4. The nonlinear processing circuit has an input/output characteristic that suppresses the passband components of the filter in a range where the input signal amplitude is smaller than a predetermined level, and emphasizes the passband components of the filter in other ranges of the input signal amplitude. A video signal processing device according to claim 1, wherein the video signal processing device is configured as follows. 5. Claims 1 to 5, wherein the nonlinear processing circuit is constituted by a read-only memory in which an input/output characteristic table is stored in advance, in which an input signal is an address and the stored content written to that address is an output signal. The video signal processing device according to any one of Item 4. 6. The nonlinear processing circuit is configured to include a plurality of input/output circuits each realizing different input/output characteristics, and selection means for selecting one of them. The video signal processing device according to any one of the above. 7. The video signal processing device according to any one of claims 1 to 6, wherein the filter is a high-pass filter. 8. The video signal processing device according to any one of claims 1 to 6, wherein the filter is a band-pass type filter.