JP2535244B2 - Television signal ghost removal device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ghost elimination device for a television signal used for a television receiver, a video device handling a television signal, and the like.

[Description of Prior Art] An example of a conventional ghost removing device will be described with reference to FIG.

Note that the processing in this example is all performed digitally.

Reference numeral 1 denotes a transversal filter which receives a television signal and corrects waveform distortion to remove a ghost component. In this embodiment, the transversal filter is constituted by a digital filter which varies a filter coefficient. In such a transversal filter, for example, the ghost component is removed by setting a filter coefficient having a phase opposite to that of the ghost component included in the input signal. Transversal filter 1
The output of is an output video signal and is also supplied to the waveform extraction circuit 2. The waveform extracting circuit 2 extracts a predetermined period including the reference signal in the television signal. This reference signal is a pattern capable of detecting the reference timing in one horizontal scanning period, and an example of a typical reference signal is the third example.
Shown in the figure.

3 (a) and 3 (b) each show a step-like signal superimposed on a part of one horizontal scanning period. In the case of FIG. 3 (a), for example, the rising edge of the step-like signal. In the case of FIG. 3B, the edge, for example, the falling edge of the step signal can be used as the reference timing.

FIG. 3 (c) shows a pulse-like signal superimposed on the vertical synchronizing signal, and in this case as well, the rising or falling edge can be used as a reference.

In the so-called 8-field sequence method, the reference signal (data) described above is obtained by subtracting the data of the predetermined other field from the data of the predetermined field from the data of the predetermined field.

A signal for a predetermined period including the specific pattern signal extracted by the waveform extracting circuit 2 is supplied to the averaging circuit 3, and the averaging circuit 3 averages noise components randomly generated in the output of the waveform extracting circuit 2. . A circuit example of the waveform extracting circuit 2 and the averaging circuit 3 is shown in FIG.

In FIG. 4, the waveform extracting circuit 2 has a gate circuit 21 that passes an input signal including a reference signal for a predetermined period, and the gate circuit 21 is controlled by a control signal from a controller (not shown). Controlled on and off. The signal of a predetermined period that has passed through the gate circuit 21 is supplied to the memory 32 via the adder 31 of the averaging circuit 3, and the output of the memory 32 is fed back to the adder 31. That is, the adder 31 supplies the result of adding the supplied input signal and the signal already written in the memory 31 and delayed by the predetermined time to the memory 32.
The output of is a noise component that is randomly present in the time axis direction and is averaged.

After performing this arithmetic averaging process a plurality of times, the gate circuit 33 is opened in response to the arithmetic average result acquisition pulse from the controller, and the arithmetic averaged signal is taken out.

Returning to FIG. 2 again, the output of the averaging circuit 3 is differentiated by the differentiating circuit 4 from the reference waveform signal (that is, the rising edge of the averaging-processed reference signal is used as the reference timing to perform the differentiation process. The obtained reference waveform signal) is obtained, and this reference waveform signal is compared with the ideal reference waveform signal generated from the reference waveform generation circuit 5 by the subtracter 6 as the comparison means. The output of the subtractor 6 is supplied to the magnification setting circuit 7 as an error signal. Magnification setting circuit 7
Defines the loop magnification, and the coefficient setting circuit 8 generates coefficient data for setting the filter coefficient of the transversal filter 1 based on the magnification set here.

As described above, the ghost is generated by the closed loop formed by the transversal filter 1, the waveform extraction circuit 2, the averaging circuit 3, the differentiation circuit 4, the subtractor 6, the reference waveform generation circuit 5, the magnification setting circuit 7, and the coefficient setting circuit 8. A removal circuit is constructed. That is, the closed loop control is performed so that the ghost component is removed by sequentially varying the filter coefficient of the transversal filter 1 according to the reference signal in the input television signal and the error signal obtained from the reference signal.

Although one example of the above-mentioned conventional technique is configured by a feedback loop, there is a ghost elimination circuit by a feedforward loop in which the waveform extraction circuit 2 is arranged on the input side of the transversal filter 1.

[Problems to be Solved by the Invention] However, when the S / N ratio of the input television signal is good as shown in FIG. 5 (a), noise is removed to some extent by the averaging process. When the S / N of the input television signal is bad as shown in (b), noise cannot be sufficiently suppressed only by the averaging processing by the averaging circuit 3, so that the ghost component included in the reference signal can be accurately detected. Disappear.

Further, when pulse noise is mixed in a predetermined period including the reference signal or when the waveform extraction circuit 2 extracts another signal other than this predetermined period, if the averaging process is performed as it is, a component different from the ghost component is ghosted. Will be regarded as.

In either case, an erroneous error signal is output from the subtractor 6, and ghost removal processing is performed according to this error data, which causes a problem in the output image.

The present invention has been made in order to overcome the drawbacks of the prior art, constantly monitoring the S / N of the input television signal, and prohibiting the setting of new coefficient data when the S / N deteriorates. At the same time, when the S / N returns to a good state, the coefficient data that determines the filter coefficient of the transversal filter is initialized so that false ghost removal is prevented and the output video signal is disturbed. It is an object of the present invention to provide a ghost eliminating device for a television signal which is not provided.

[Means for Solving the Problem] In order to achieve such an object, the present invention includes a transversal filter provided in an input television signal path, and a predetermined period including a reference signal for ghost detection from a television signal. Signal is extracted, the rising edge in the extracted reference signal is used as the reference timing, the reference waveform signal is obtained based on this reference timing, and the ideal reference waveform signal and the reference waveform signal output from the reference waveform generation circuit The ghost of the television signal is removed by setting the coefficient data by the coefficient setting circuit according to the error signal and the processing block that obtains the error signal by comparing with, and changing the filter coefficient of the transversal filter by this coefficient data. The S / N measuring circuit for monitoring the S / N of the input television signal and the S / N measuring device. When it is determined that the S / N has deteriorated according to the measurement result of the constant circuit, prohibiting the change of the filter coefficient by the coefficient setting circuit,
When it is determined that the S / N of the input television signal has returned to a good state, the filter coefficient change prohibition is released and the S / N determination circuit that controls the processing block so that the coefficient data is initialized. It is characterized by having.

[Operation of the Invention] According to the ghost elimination device for a television signal having the above-described configuration, when the S / N of the input television signal is poor, for example, noise is not sufficiently eliminated even by averaging processing,
Since the filter coefficient is not changed, deterioration of the output image can be suppressed. If the S / N returns to a good state again, the past ghost state and the current ghost state may be different.Therefore, by initializing the coefficient data generated, the current ghost state It is possible to generate coefficient data according to the above.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. The same parts as those described in the description of the prior art are designated by 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 removing apparatus of the present invention.

In the figure, a ghost elimination device by closed loop control by a transversal filter 1, a waveform extraction circuit 2, an averaging circuit 3, a differentiation circuit 4, a basic waveform generation circuit 5, a subtractor 6, a magnification setting circuit 7, and a coefficient setting circuit 8 is configured. What is done is the same as in the case of the prior art shown in FIG.

In the present embodiment, the output of the waveform extracting circuit 2 is supplied to the averaging circuit 3 and also to the S / N measuring circuit 10. The S / N measuring circuit 10 is, as shown in FIG.
The S / N is measured over a predetermined period of the reference signal, and the measured S / N data is supplied to the S / N determination circuit 11. Further, the S / N data at this time is also given to the averaging circuit 3 so as to be also used as data for determining the number of additions of the averaging process. Based on this data, the averaging circuit 3 determines the number of additions so that the number of additions is small when the S / N is good and the number of additions is large when the S / N is bad.

The S / N judgment circuit 11 is the S / N supplied from the S / N measurement circuit 10.
Based on the data of S / S, S / S that is sufficient to suppress the random noise component by the averaging process by the averaging circuit 3
It is determined whether it is N or not. Specifically, how much S / N can be removed can be determined in advance from experimental data or the like. The S / N judgment circuit 11 is also supplied with time data from the timer 12, which distinguishes between instantaneous S / N deterioration (pulse noise component) and continuous S / N deterioration. It is for doing.

When the S / N determination circuit 11 determines that the noise component that cannot be completely removed by the averaging process is included, the hold signal is output from the S / N determination circuit 11 to the coefficient setting circuit 8. The coefficient setting circuit 8 that has received the hold signal
The generation of new coefficient data is prohibited and the immediately preceding coefficient data is retained. By doing so, even if an erroneous error signal is output from the subtractor 6 due to a noise component included in the input television signal, correction corresponding to this is not performed, and an adverse effect on the output image is prevented.

Next, when the S / N returns to a good state, the hold signal is released, and the processing block 9 includes the waveform extraction circuit 2, the averaging circuit 3, the differentiating circuit 4, the subtractor 6, and the magnification setting circuit 7. In response, a reset signal is output. Receiving the reset signal, each circuit in the processing block 9 is reset so that the coefficient data set by the coefficient setting circuit 8 is initialized. The initialization of the coefficient data means that the coefficient data can be newly set from the beginning without being affected by the coefficient data before that.
Therefore, if the coefficient data is initialized when the S / N returns to a good state, the coefficient data is reset from the time when the S / N becomes a good state, and the past ghost state ( The coefficient data is generated according to the current ghost state without being affected by noise).

Further, since the S / N determination circuit 11 does not respond to the temporary deterioration of S / N due to the sudden pulse noise due to the action of the timer 12, the reset signal is frequently supplied to the processing block 9. Never give.

In the above embodiment, the coefficient setting circuit 8 holds the immediately preceding coefficient data by the hold signal, but it is also possible to preset the coefficient data and output it. Further, it is not necessary to reset all the circuits in the processing block 9 by the reset signal, and the point is that only the circuits required for initializing the coefficient data generated by the coefficient setting circuit 8 need to be reset. Of course.

[Effects of the Invention] As described above, according to the ghost elimination device for a television signal of the present invention, the S / N of the input television signal is constantly monitored, and the ghost elimination is performed when the S / N deteriorates. Since the change of the filter coefficient of the transversal filter to be performed is prohibited, the adverse effect on the output image can be prevented when an erroneous error signal is generated by the noise component.

Moreover, since the coefficient data is initialized when the S / N returns to a good state, it is possible to prevent the adverse effect on the generation of the coefficient data due to past noise.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a television signal ghost removing apparatus of the present invention, FIG. 2 is a block diagram showing an example of a configuration of a conventional ghost removing apparatus, and FIG. 3 is a specific pattern signal. FIG. 4 is a waveform diagram showing an example of FIG.
And FIG. 2 is a block diagram showing in detail the configuration of a part of FIG.
FIG. 5 is a waveform diagram showing an example of the noise component of the waveform of the specific pattern signal superimposed on the television signal. 1 ... Transversal filter, 2 ... Waveform extraction circuit, 3 ... Addition / averaging circuit, 4 ... Differentiation circuit, 5 ... Reference waveform generation circuit, 6 ... Subtractor, 7 ... Magnification setting circuit, 8
…… Coefficient setting circuit, 10 …… S / N measurement circuit, 11 …… S / N judgment circuit, 12 …… Timer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuji Takaguchi 3-12 Moriya-cho, Kanagawa-ku, Yokohama, Kanagawa Japan Victor Company of Japan, Ltd.

Claims (1)

(57) [Claims] 1. A transversal filter provided in an input television signal path, a signal for a predetermined period including a reference signal for ghost detection is extracted from a television signal, and a rising edge in the extracted reference signal. An edge or the like is used as a reference timing, a reference waveform signal is obtained based on this reference timing, and a processing block that obtains an error signal by comparing the ideal reference waveform signal output from the reference waveform generation circuit with the reference waveform signal, A ghost elimination device for eliminating ghosts of a television signal by setting coefficient data by a coefficient setting circuit according to the error signal and varying a filter coefficient of the transversal filter according to the coefficient data. S / N measurement circuit that monitors the S / N of the John signal, and the S / N according to the measurement results of this S / N measurement circuit When it is determined that the filter coefficient is changed, it is prohibited to change the filter coefficient by the coefficient setting circuit, and when it is determined that the S / N of the input television signal has returned to a good state, the change of the filter coefficient is prohibited. The processing block is controlled so that the coefficient data is initialized while being canceled.
A ghost eliminating device for a television signal, comprising: an S / N judging circuit.