JP2770579B2 - Noise removal device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise removing device for removing a noise component of a video signal in a laser player, a video tape recorder or the like.

[0002]

2. Description of the Related Art A conventional noise removing apparatus will be described below.

FIG. 6 is a block diagram showing a conventional noise removing apparatus. In FIG. 6, first, an input video signal input to a video signal input terminal 609 is extracted by a band-pass filter (hereinafter, referred to as BPF) 601 only for a video signal in a predetermined frequency band. The output of the BPF 601 is limited to a predetermined value by a limiter 602, and the adder 603 adds the signal to an input video signal, thereby removing noise in a frequency band extracted from the input video signal by the BPF 601. This is a configuration when the phase of the video signal is inverted by the BPF 601. If the phase is not inverted, the output of the limiter 602 may be subtracted from the input video signal using a subtractor instead of the adder 603. In addition, BPF6
Since 01 is simply limited in frequency band, its output contains not only a noise component but also a video signal component. If the value limited by the limiter 602 is too large, adverse effects such as degradation in resolution of the video signal occur. Therefore, the value must be set to an appropriate value depending on the balance between the degree of noise component removal and the degree of deterioration of the video signal. BP
The portion configured by F601, limiter 602, and adder 603 is a noise removal circuit 607. Noise removal circuit 60
8 has exactly the same configuration. By changing the frequency band of the video signal extracted by the BPF 604 and the value limited by the limiter 605, a noise removing effect different from that of the noise removing circuit 607 can be obtained. Thus, the noise removal circuit 60
7, 608 are cascaded to output a video signal from which noise components in two frequency bands have been removed to a video signal output terminal 610. Of course, if the noise to be removed is only in the frequency band that can be realized by one BPF 601, only the noise removal circuit 607 may be used.

[0004]

However, the above conventional configuration has the following two problems.

[0005] First, if the noise to be removed is dispersed in L (L is a natural number) frequency bands, the BPF is connected in cascade with N (N is a natural number, where N ≦ L) noise removing circuits. Although N is required, the problem is that the circuit scale increases in proportion to N since the overall circuit scale is almost entirely dependent on the BPF circuit scale. The conventional example of FIG. 6 has a configuration of N = 2.

[0006] The second problem is as follows. FIG.
Is realized by a digital circuit when ± M (M
Is limited to a natural number), the entire value ± M must be determined, and a decoder composed of complicated gates is required. Further, if M is set to 2 ^m (m is a natural number), the limit can be limited to −M to + (M−1) with a simple gate.
That is, if the limiter is not sufficiently small, the circuit scale of the limiter is smaller than that of a gate implemented by a ROM (read only memory). However, the problem is that the circuit scale is still large even if it is embodied in ROM.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a noise eliminator in which the entire circuit scale is reduced.

[0008]

In order to achieve this object, a first object of the present invention is to provide a noise eliminator for filtering predetermined L (L is a natural number) frequency bands of an input video signal. , N (N is a natural number, where N ≦ L) signals, a band-pass filter that outputs N signals, and a limiter that outputs N signals by limiting the N outputs to predetermined values. A first adder for adding the outputs,
A second adder for adding the output and the input video signal.

According to a second aspect of the present invention, there is provided a noise removing apparatus comprising: a band-pass filter for filtering a predetermined frequency band of an input video signal; a limiter for limiting an output of the input video signal to a predetermined value; A gate circuit that calculates the output of the filter and outputs a binary signal whose level changes only when the value is equal to or more than a predetermined value or less, and an adder that adds the output of the filter, the input video signal, and the output of the limiter. It has.

[0010]

According to the present invention, the following effects can be achieved with respect to the first problem by the above-described structure. The BPF usually implements a required frequency characteristic by cascading a plurality of filters. For example, two BPFs required when N = 2
Among them, the filter units having similar frequency characteristics are shared. By cascade-connecting filters having different frequency characteristics to the shared filter unit, if the respective frequency characteristics are realized and input to the limiter, the circuit scale can be reduced by the amount of the shared filter unit.

The second problem has the following operation. As described above, when the limiter is limited to ± M, if M is set to 2 ^m , the limiter can be realized by a simple gate that limits to −M to + (M−1), and the output of the BPF is M in the gate circuit. If the above signal is output as a high level, otherwise it is output as a low level, and if the signal is input to the carry input of the least significant bit of the adder for adding the input video signal and the output of the limiter, the BPF When the output of M is equal to or more than M, 1 is added by the adder, which is equivalent to limiting to ± M by the limiter. This allows
The limiter, which has conventionally been embodied in a ROM, is replaced with a gate, and the circuit scale can be reduced. Only the gate circuit increases as a circuit, and there is no problem because its scale is very small as compared with the reduction by replacing with a gate.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the noise elimination device according to the present invention will be described below with reference to the drawings.

However, the same components as those of the conventional noise eliminator shown in FIG. 6 are denoted by the same reference numerals, and the description of the operation is omitted.

FIG. 1 is a diagram showing the noise in the first embodiment of the present invention.
FIG. 2 is a block diagram showing the configuration of a noise removal device, and FIG.
It is a wave number characteristic diagram. However, in the embodiment when N = 2,
You. The frequency characteristics of the BPF 101 shown in FIG.
The frequency characteristics of the PF 102 are shown in FIG.
FIG. 2D shows frequency characteristics. As shown in FIG.
In addition, the frequency characteristic of the BPF 101 is the frequency band f_xsmell
Frequency f₁Is the gain g ₁Is a BPF that passes through
You. In addition, as shown in FIG.
The numerical characteristic is the frequency band f_xAt frequency 0, f₁, F_x
Is the gain g₁Is a BPF that allows the light to pass through. This B
Circumference obtained by cascade connection of PF101 and BPF102
The wave number characteristic is, as shown in FIG._xTo
Frequency f₁Is the gain g₁And the frequency f_Two, F_ThreeGay
G_TwoTo pass through. Similarly, BPF 101
Frequency characteristics obtained by cascade connection of
As shown in FIG. 2 (e), the frequency band f_xFrequency at
Number f₁Is the gain g₁And the frequency f_Four, F_FiveIs the gain g_Fourso,
Frequency f₆, F₇Is the gain g₆With something that passes through
Become. The frequency characteristic of FIG. 2C corresponds to the BPF 60 of FIG.
2 is the same as the frequency characteristic of FIG.
6 is the same as the frequency characteristic of the BPF 604. That is,
The BPF 601 in FIG. 6 is the BPF 101 and the BPF 10 in FIG.
2 are connected in tandem, and the BPF 604 in FIG.
It is assumed that 101 and BPF103 are connected in cascade.
May be. Thus, the BPF 601 and the BPF 6 in FIG.
04, the common part of the BPFs
101 and shared. Limit output of BPF102
Input to the data 602 to limit it to a predetermined value. Similarly, B
Input the output of PF103 to limiter 605 and set it to a predetermined value
Limit. Consists of limiter 602 and limiter 605
The portion to be performed is referred to as a limiter 107. Exit of limiter 602
The power and the output of the limiter 605 are added by the adder 104, and
Further, the adder 105 adds the input video signal. This
Noise components extracted by BPF101 and BPF102.
And noise extracted by BPF101 and BPF103
The video signal from which the component has been removed is output to the video signal output terminal 610.
Power.

As described above, according to this embodiment, FIG.
By using a common configuration as the BPF 101 among the BPFs constituting the PF 601 and the BPF 604, the common portion can be reduced by the circuit size of the BPF 101.

FIG. 3 is a block diagram showing a configuration of a noise eliminator according to a second embodiment of the present invention, and FIG. 4 shows a specific circuit example of a limiter and a gate circuit according to the second embodiment of the present invention. . In the second embodiment, the BPF 601 and the limiter 60 in the conventional noise elimination device shown in FIG.
2. It is assumed that digital signal processing is performed on the portion constituted by the adder 603. An analog-to-digital converted video signal is input to a video signal input terminal 305, and a BPF 301
Extracts only video signals in a predetermined frequency band. Here, for example, the output of the BPF 301 is an 8-bit digital signal like the BPF output signal 403 shown in FIG. BP
The F output signal 403 has the most significant bit as the most significant bit and the least significant bit as the least significant bit. The bits are arranged in order, have a dynamic range of -128 to +127, and are represented by offset binary. And The BPF output signal 403 is input to the limiter 302,
Suppose that it is limited to 4 bits of +7. For this purpose, first, the upper 5 bits are input to the flow detection circuit 401, and the BP
The F output signal 403 outputs a low level signal when -128 to -9, ie, underflow, or +8 to +127, ie, overflow, and outputs a high level signal otherwise, ie, -8 to +7. This signal and the sign bit and the lower 3 bits of the BPF output signal 403 are input to the gate 402, and the sign bit is output when the output of the flow detection circuit 401 is at a high level, and the lower 3 bits signal is output when the output of the flow detection circuit 401 is at a low level. Output. As a result, the limiter 302 outputs a 4-bit limiter output signal 404 that limits the BFP output signal 403 to -8 to +7. On the other hand, the upper 5 bits of the BPF output signal 403 are input to the gate circuit 303, and the BPF output signal 403
The gate circuit output signal 405 is set to a high level when the value is 8 or more, and to a low level otherwise. Then, the output of the limiter 302, that is, the limiter output signal 4
When the adder 304 and the input video signal are added by the adder 304, if the output of the gate circuit 303, that is, the gate circuit output signal 405 is input to the carry input of the least significant bit, B
When the PF output signal 403 is greater than or equal to +8, only one is added, which is equivalent to limiting the limiter 202 to ± 8. As described above, the adder 304 adds the input video signal, the output of the limiter 302, and the output of the gate circuit 303, and outputs a signal from which only the noise component extracted by the BPF 301 has been removed to the video signal output terminal 306.

FIG. 5 is a block diagram showing a configuration of a noise removing device according to a third embodiment of the present invention. This third embodiment is constructed by combining the first embodiment of FIG. 1 and the second embodiment of FIG. 3, and performs digital signal processing on the first embodiment. The operation is exactly the same as that of FIG. , Have the effects of the first embodiment and the second embodiment. Note that the output of the gate circuit 506 may be input to the adder 508, and the output of the gate circuit 507 may be input to the adder 509.

[0018]

As described above, the present invention provides a band-pass filter 106 for filtering predetermined L frequency bands of an input video signal and outputting N signals, and outputting the N outputs to a predetermined number. A limiter 107 for limiting the output to N values and outputting N signals; a first adder 104 for adding the N outputs; and a second adder 104 for adding the output and the input video signal.
, The circuit scale can be reduced.

Also, the present invention provides a band pass filter 301 for filtering a predetermined frequency band of an input video signal, a limiter 302 for limiting the output of the input video signal to a predetermined value, and an output of the band pass filter 301 for calculating a predetermined value. The circuit includes a gate circuit 303 that outputs a binary signal whose level changes only at the time of or above or below, and an adder 304 that adds the output thereof, the input video signal, and the output of the limiter 302. The scale can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a noise removing device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an example of a frequency characteristic of a BPF in the noise elimination device of the present invention.

FIG. 3 is a block diagram illustrating a configuration of a noise removing device according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram showing a specific circuit example of a limiter and a gate circuit in a second embodiment.

FIG. 5 is a block diagram showing a configuration of a noise removing device according to a third embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a conventional noise removing device.

[Explanation of symbols]

101 to 103, 106, 301, 501 to 503 B
PF 107, 302, 504, 505, 511, 602, 6
05 Limiter 104, 105, 304, 508, 509 Adder 303, 506, 507 Gate circuit 401 Flow detection circuit 402 Gate 305, 609 Video signal input terminal 306, 610 Video signal output terminal

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Inoue 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-63-99608 (JP, A) JP-A-60-169292 (JP, A) JP-A-63-20969 (JP, A) JP-A-63-164678 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 5/93 H04N 5/21

Claims (4)

(57) [Claims] A band-pass filter for filtering a predetermined frequency band of an input video signal; a limiter for limiting an output of the band-pass filter to a predetermined value; and a predetermined value for calculating an output of the band-pass filter. A gate circuit that outputs a binary signal whose level changes only at the time of or above or below, an adder that adds the output of the gate circuit, the input video signal, and the output of the limiter Noise removal device. 2. A predetermined L number of input video signals (L is a natural number)
, Each of which filters N frequency bands and outputs N (N is a natural number, where N ≦ L) signals; and N outputs of the band-pass filter are limited to predetermined values, respectively. A first adder that adds the N outputs of the limiter, and a second adder that adds the output of the first adder and the input video signal. provided, N is the set to 2, and the band-pass filter, the input
First band pass for filtering a predetermined frequency band of a video signal
A filter and a predetermined output of the first bandpass filter.
A second bandpass filter for filtering the frequency band of
The predetermined frequency band of the output of the first band-pass filter is
And a third band-pass filter for filtering.
The output of the band-pass filter of FIG.
Of the third band-pass filter
The output of the filter as the second output of the bandpass filter.
That noise removal device. 3. A predetermined L number of input video signals (L is a natural number)
, Each of which filters N frequency bands and outputs N (N is a natural number, where N ≦ L) signals; and N outputs of the band-pass filter are limited to predetermined values, respectively. And a limiter that outputs the signal of
N number of gate circuits that output N binary signals whose level changes only when the level is equal to or more than or equal to or less than a predetermined value; A first adder for adding the output and the N outputs of the limiter; and adding the output of the first adder and the output of the N gate circuits in the first adder. A noise removing device comprising: one output that has not been output; and a second adder that adds the input video signal. 4. A first band-pass filter for filtering a predetermined frequency band of an input video signal, and a band-pass filter for filtering a predetermined frequency band of an output of the first band-pass filter. A second band-pass filter, and a third band-pass filter for filtering a predetermined frequency band of the output of the first band-pass filter. The output of the second band-pass filter is band-passed. 4. The noise eliminator according to claim 3, wherein a first output of the two outputs of the filter is a first output, and an output of the third band-pass filter is a second output of the band-pass filter.