JPH0355973A - Noise suppression device for television signal - Google Patents

Abstract

PURPOSE:To reduce quantization noise and random noise by improving the resolution of input and output television signals and revising an output level of an arithmetic means depending on the amplitude of the input television signal. CONSTITUTION:The resolution of an input television signal A inputted from an input terminal 1 is increased to 8-bit from a conventional 6-bit. A high-order 6-bit signal An of the input television signal A and an output signal Bn (6-bit) of a delay device 2 are inputted to a subtraction circuit 3 and a difference signal Cn is inputted to an arithmetic unit 4. Thus, when the level of the input television signal is small, quantization noise being a problem is reduced and a correction value Dn being an output of the arithmetic unit 4 is decreased when the level of the input signal An is small to suppress production of quantization noise due to the arithmetic error and when the level is large, sufficient random noise is suppressed with a conventional correction value.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a noise suppression device for television signals. [Prior Art] In general, in TV playback images, if the image is moving, deterioration in image quality due to noise is not a visual problem, but if the image has little movement or is a still image, deterioration in image quality due to noise may occur. The deterioration in image quality becomes difficult to ignore.
In order to prevent image quality deterioration due to such noise, a device shown in Fig. 2 has been used in the past. That is, input terminal l
The television signal A added from the input signal A and the output B of the delay device 2 (the television signal before the L field) are added to the subtraction circuit 3 to obtain a difference signal C (C=A-B), and this difference signal C is It is given to the coefficient unit 7 as an address signal, and the value corresponding to that address is obtained as the output D. The output D is applied to the difference bow C in response to the difference signal C by a variable coefficient 1K (0≦K≦1
), which is D--K (A-B). This output D is added to the input television signal A by an adder circuit 5 to obtain a television signal Y with noise suppressed. 6 is the output terminal. Therefore, Y=A-K (A-B). When the difference signal C has a value close to zero, that is, in a part that is considered to be a stationary part of copying, when the difference signal C is positive (A>B), a negative value is read out from the coefficient unit 7, and the difference signal C is negative(
When A<B), a positive value is read from the coefficient unit 7. or,
When the absolute value of the difference signal C is larger than a certain value, that is, in a moving image part, zero is read out from the coefficient unit 7. Here, a brief explanation of the noise suppression operation is as follows. In the case of a still image, if n field images are added one after another and the average is calculated, the correlated image signal remains unchanged, while the uncorrelated mixed noise has an average amplitude of 1/J7. , noise reduction becomes possible. However, if this operation is performed simply, problems such as blurring of the image or tails may occur in video parts where field correlation is low, so the above-mentioned measures have been taken. [Problems to be Solved by the Invention] In the above-mentioned conventional television signal noise boosting device, the resolution is generally 6 bits. Errors can no longer be ignored. That is, in addition to random noise, quantization noise occurs due to calculation errors, and there is a problem in that the signal-to-noise ratio deteriorates significantly, especially for signals with small amplitudes. Another problem was that simply increasing the resolution would increase the memory capacity and increase costs. This invention was developed to solve the above-mentioned problems, and provides an inexpensive television that can suppress random noise of large amplitude signals without deteriorating the S/N ratio of small amplitude signals. The purpose of the present invention is to obtain a noise suppression device for John signals.

(Means for Solving the Problems) A television signal noise suppression device according to the present invention includes a signal delaying means that delays an output television signal and has a resolution of n bits, and a human power having a resolution of m bits where m>n. a subtraction means for outputting a difference signal between the television signal and the signal delay means; a calculation means for outputting a correction value signal having a level corresponding to the difference signal and corresponding to the level of the human-powered television signal; This system is equipped with an adding means for adding the input television digital signals and outputting an output television signal with m-bit resolution. [Function] In this invention, the resolution of the human-powered television signal and the output television signal is increased, and the output level of the calculation means is changed depending on the amplitude of the input television signal, thereby reducing signal deterioration due to quantization. In particular, noise caused by calculation errors in small-amplitude signals is suppressed, and random noise in large-amplitude signals is also suppressed.
[Examples] Examples of the present invention will be described below with reference to the drawings. 1st
The figure shows the arrangement of the television signal noise suppression device according to this embodiment, where 1 is the input terminal for the television signal, 2 is the delay device, 3 is the subtraction circuit, 4 is the arithmetic device, 5 is the addition circuit, and 6 is the These are output terminals, A, An, Bn, Cn, Dn,
Both Y and Yn represent signals. In the above structure, the resolution of the human-powered television signal A input from the input terminal l is increased from the conventional 6 bits to 8 bits.
Let it be a bit. The signal An of the upper 6 bits of this human-powered television signal 8 and the output signal Bn (6 bits) of the delay device 2 are manually input to the subtraction circuit 3. The difference signal Cn, which is the output of the subtraction circuit 3, is input to the arithmetic unit 4, which outputs a correction value Dn corresponding to the difference signal Cn.
n is added to the upper 6 bits of the human-powered television signal A to obtain an output television signal Y with 8-bit resolution and noise suppressed. Further, the signal Yn of the upper 6 bits of the output television signal Y is inputted to the delay device 2.

In the operation of the arithmetic unit 4', when the difference signal Cn, which is considered to be a static part of the image, has a value close to zero, the difference signal Cn is positive (A
n > B r+ ), a negative value is output, and when the connecting bow Cn is negative (An<Bn), a positive value is output.

On the other hand, if the absolute value of the difference signal Cn, which is considered to be a moving image part, is a certain value or more, a zero is generated. This is similar to the coefficient unit 7 of the conventional device, but differs from the conventional device in that the arithmetic unit W4 changes its output level depending on the level of the input signal An. For example, when the level of the input signal A is high, that is, when the brightness and color saturation are high, the quantization noise is inconspicuous and the random noise suppression effect is large, so the correction value Dn similar to the conventional one is output. When the level of the input signal A is low, that is, when the brightness and color saturation are low, the generation of quantization noise due to calculation errors is more noticeable than the effect of suppressing random noise, so a smaller correction {i D n is output than before. death,
It has the effect of suppressing quantization noise caused by calculation errors and large random noise. As described above, in this embodiment, by increasing the resolution of the input signal A and output signal Y from the conventional 6 bits to 8 bits, the quantization noise that becomes a problem when the level of the human-powered television signal is small is reduced, and the calculation When the level of the input signal An is low, the correction value Dn, which is the output of the device W4, is made small to suppress the occurrence of quantization noise due to calculation errors. When the level of the input television signal is high, the quantization noise is not noticeable, so the conventional correction value can provide sufficient random noise suppression. [Effects of the Invention] As described above, according to the present invention, quantization noise is reduced by human effort and by increasing the resolution of the output television signal, and the output level of the calculation means is changed depending on the amplitude of the input television signal. By doing so, it is possible to reduce quantization noise in the case of a small amplitude signal, and to reduce random noise in the case of a large amplitude signal. Furthermore, since there is no need to increase the resolution of the calculation means, etc., there is no need to increase the memory capacity, and the device can be made inexpensive.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the inventive device, and FIG. 2 is a block diagram of a conventional device. 2...Delay device, 3...Subtraction circuit, 4...Arithmetic device, 5...Addition circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] a signal delay means for delaying an output television signal and having n-bit resolution; and a subtraction means for outputting a difference signal between an input television signal having an m-bit resolution where m>n and the output of the signal delay means; a calculation means that receives a difference signal and an input television signal and outputs a correction value signal corresponding to the difference signal, the correction value signal having a level corresponding to the level of the input television signal; 1. An apparatus for suppressing noise in a television signal, comprising an adding means for adding together an input television signal and outputting an output television signal with m-bit resolution.