JPH0423681A - Ghost elimination device for television signal - Google Patents

Abstract

PURPOSE:To prevent malfunction of ghost elimination by providing a band limit means and giving a low pass filter coefficient eliminating an undesired high frequency component to a coefficient data set to a transversal filter corresponding to the effect due to a component of a reference signal at the outside of a frequency band. CONSTITUTION:An output of a coefficient setting circuit 2 is fed to a counter 7. The counter 7 counts number of times when the coefficient setting circuit 2 generates a coefficient data till the ghost elimination state is converged. Then when number of times reaches a prescribed number of times or over, a band limit circuit 8 is activated. The band limit circuit 8 gives a low pass filter coefficient having a predetermined frequency characteristic to a transversal filter 1. Thus, an undesired high frequency component other than the frequency band component possessed by a reference signal is not outputted to the output of the transversal filter 1 and the loop is quickly converged to the correct converging state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ghost removal device for a television signal used in a television receiver or a video set that handles television No. 13.

[Prior Art 1 An example of a conventional ghost removal device will be described with reference to FIG. 3.

1- is a transversal filter that receives a television signal as input, corrects waveform distortion, and removes ghost components; in this example, it is composed of a digital filter with variable filter coefficients. , such a transversal filter can be used, for example, by setting filter coefficients that are in opposite phase to the ghost component contained in the input signal.
It becomes possible to remove ghost power. The output of the transversal filter 1 becomes an output video signal and is also supplied to the waveform extraction circuit 3. The waveform extraction circuit 3 extracts a predetermined period including a specific pattern signal from a television signal, performs predetermined waveform conversion such as differentiation as necessary, and outputs the extracted period. This specific pattern signal is a pattern by which the reference timing in one horizontal scanning line period can be detected, and an example of a typical specific pattern signal is shown in FIG.

4(a) and 4(b) each show a step-like signal superimposed on a part of one horizontal scanning period, and in the case of FIG. 4(a), for example, the rising edge of the step-like signal In the case of FIG. 11(b), for example, the falling edge of the step signal can be used as the reference timing. For example, by differentiating the falling-edge portion of the step-like signal shown in FIG. 4(b), a pulse-like signal as shown in FIG. 4(c) is obtained. Figure 4 (d
) is a narrow step-like signal superimposed on the vertical synchronization signal, and in this case as well, the rising or falling edge can be used as the reference timing.

The specific pattern signal extracted by the waveform extraction circuit 3 is subjected to waveform conversion processing such as differentiation, and is compared with a reference signal generated from the reference waveform generation circuit 5 by a discarder 4 serving as comparison means. The output of the smearer 4 is supplied to the magnification setting circuit 6 as an error signal. The magnification setting circuit 6 determines a magnification for determining the filter coefficient to be set in the transversal filter 1, and based on the magnification set here, the coefficient setting circuit 2
Generate a coefficient take for setting the filter coefficients of .

As described above, a ghost removal circuit is formed by the closed loop formed by the transversal filter 1, the waveform extraction circuit 3, the 'g'H unit 4, the reference signal generation circuit 5, the magnification setting circuit 6, and the coefficient setting circuit 2. . That is, the reference timing is obtained from a specific pattern of words in the input television signal, and the filter coefficients of the transversal filter 1 are successively varied in accordance with the error signal obtained from this reference timing and the reference signal, thereby removing the ghost component. closed-loop control is used to eliminate the

E Problems to be Solved by the Invention] However, since the coefficient data set by the coefficient setting circuit 2 is not band limited, the frequency band components of the coefficient data are components other than the frequency band components of the reference signal (high frequency band components). The transversal filter 1 may perform an incorrect filtering action due to the out-of-band components. In such a case, there is a drawback that the convergence to an erroneous ghost state or the convergence to the ghost removal device is delayed.

The present invention has been made in order to overcome the drawbacks of the prior art as described above, and when generating a coefficient take to be set in a transversal filter, the frequency band of the reference waveform is determined for the coefficient data. A low-pass filter coefficient having a characteristic of passing only the frequency component and blocking other frequency components (high-frequency components) is given to the coefficient data set in the transversal filter to prevent malfunction of the ghost removal function. It is an object of the present invention to provide an apparatus for removing ghosts from television signals.

[Means for Solving the Problems 1] In order to achieve the above object, the present invention includes a transversal filter provided in the input television (ej) path, and detects a specific pattern No. 48 for ghost detection from the television signal. By extracting a signal of a predetermined period including the specified pattern signal, comparing the reference timing in the specific pattern signal with the reference signal, setting coefficient data according to the detected error signal, and varying the filter coefficient of the transversal filter. A ghost removal device that removes ghosts from television signals, in which a transversal filter is set with a low-pass filter coefficient that removes unnecessary high-frequency components of coefficient data in response to the influence of components outside the frequency band of the reference signal. The present invention is characterized in that it has a band limiting means for applying coefficient data to be processed.

[Action 1 of the Invention] According to the television signal ghost removal device having the above configuration, the coefficient data for setting the filter coefficients of the transversal filter can be made free of unnecessary band components. As a result, it is possible to reduce the adverse influence of the out-of-frequency band components of the reference waveform, prevent malfunction of the ghost removal effect, and quickly converge to the ghost removal state.

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2. ) Note that the same parts as those described in the description of the prior art are given the same reference numerals, and the description thereof will be omitted as appropriate.

FIG. 1 is a block diagram showing the configuration of an embodiment of a television signal ghost removal apparatus according to the present invention.

In the figure, the ghost removal device is constructed by closed-loop control by an I.Rance versal filter 1, a waveform extraction circuit 3, an annihilator 4, a reference signal generation circuit 5, a magnification setting circuit 6, and a coefficient setting circuit 2. This is the same as the case of the prior art shown in .

In this example, the output of the coefficient setting circuit 2 is roughly supplied to the counter 7 (detection means). The counter 7 has a coefficient setting circuit 2
The number of times coefficient data is generated is counted, and when the number of times exceeds a predetermined number, the band limiting circuit 8 (band limiting means) is activated. The band-limiting circuit 8 provides the transversal filter l with a low-pass filter coefficient having a predefined frequency characteristic shown in FIG. 2.

Next, the operation of the above embodiment will be explained.

The filter coefficients of the transversal filter 1 are made variable based on the coefficient data generated by the coefficient setting circuit 2, and the ghost removal effect is performed as is conventional (・1
．． The same is true for i. If the coefficient data contains unnecessary high-frequency components outside the frequency band of the base signal, the ghost cannot be completely removed in one minute. In this embodiment, the closed loop control is repeated until the ghost is sufficiently suppressed, and each time new coefficient data is generated by the coefficient setting circuit 2. The first coefficient data always contains unnecessary high-frequency components.
It is desirable to apply an unnecessary high-frequency component removal filter every time coefficient data is calculated. However, then
Since the processing time becomes long, the number of calculations is counted by a counter 7, and each time the count value reaches a predetermined value, unnecessary high frequency component removal processing is performed. At this time, the counter 7 activates the band-limiting circuit 8, so that unnecessary high-frequency components other than the frequency band components included in the reference signal are no longer output from the output of the transversal filter 1, and the loop quickly converges to the correct convergence state. It turns out.

[Effect of the invention 1 As described above, according to the present invention, unnecessary high-frequency components outside the frequency band of the reference signal are removed in response to the influence of components outside the frequency band of the reference signal. ,
Malfunctions of the loop for ghost removal and delays in convergence can be prevented.

[Brief explanation of the drawing]

FIG. 1 does not show the configuration of an embodiment of the television signal ghost removal device of the present invention)l2! Tsuku diagram, Figure 2 is the 1st
Figure 3 is a block diagram showing the configuration of an example of a conventional television signal ghost removal device, and Figures 4 (a) to (d) are This is a waveform diagram showing an example of the waveform of the specific Bakun atonement included, and a waveform obtained by differentially processing the waveform. 1. Transbar-Nor filter, 2. Coefficient setting circuit, 3. Waveform extraction circuit, 4. Subtractor, 5. Reference signal generator, 6. Magnification setting circuit, 7. Counter (detection means), 8.
- Bandwidth limiting circuit (bandwidth limiting means). Mochi'F Applicant Agent of Victor Company of Japan Patent Attorney fiii *Yoshio 2nd cause

Claims (1)

[Scope of Claims] A transversal filter is provided in an input television signal path, and a signal of a predetermined period including a specific pattern signal for ghost detection is extracted from the television signal, and a reference signal in the specific pattern signal is A ghost removal device that removes a ghost from a television signal by setting coefficient data according to an error signal obtained by comparing timing and a reference signal and varying a filter coefficient of the transversal filter, the ghost removal device comprising: The method further includes band limiting means for applying a low-pass filter coefficient to the coefficient data set in the transversal filter for removing unnecessary high-frequency components of the coefficient data in response to the influence of components outside the frequency band of the reference signal. Features: Television signal ghost removal device.