JPH0231567A - Ghost removing effect diagnosing device - Google Patents

Abstract

PURPOSE:To prevent occurrence of deterioration in picture quality when waveforms deteriorate by ghost removal by automatically separating the ghost removing output. CONSTITUTION:A comparing means 7 performs comparison in magnitude between a result of a preremoval correlation calculating means 4 and that of a post-removal correlation calculating means 6 and controls a switching means 8 in accordance with a compared result. When the output value of the means 6 is smaller than that of the means 4, the means 8 supplies ghost-removed received TV signals supplied from a ghost removing section 1 to an output terminal OUT, because it is considered that the ghost-removed signals are closer to information having an ideal waveform. When the output value of the means 6 is larger than that of the means 4, on the contrary, the means 8 supplies signals before removal of ghost, namely, received TV signals supplied from an input terminal IN to the output terminal OUT. Therefore, deterioration in picture quality can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a ghost removal device for removing ghosts contained in received television signals, and more particularly to a device having a function of diagnosing the ghost removal effect.

2. Description of the Related Art As shown in FIG. 3, a conventional ghost removal device includes a reference waveform extraction means 31, a Fourier transform section 32, a reference waveform Fourier coefficient holding section 33, a division section 34, a correction section 35, an inverse Fourier transform section 36, It is composed of a tap gain holding register section 37 and a removal filter section 38.

On the other hand, on the transmission side of the television signal, a reference waveform signal 5 for ghost detection as shown in FIG.
6(t) is inserted.

This reference waveform signal So (t) is obtained by band-limiting the impulse waveform by passing it through a low-pass filter circuit having an amplitude versus frequency characteristic as shown in FIG. 4(B).

Further, the reference waveform Fourier coefficient holding means 33 in FIG. 3 stores a discrete Fourier coefficient group R(jω) created by Fourier transforming the reference waveform signal 50(1) shown in FIG. is held in advance. This Fourier coefficient group R
(jω) is nothing but a low-pass amplitude versus frequency characteristic expressed by a group of discrete sampling values as shown in FIG. 4(B).

The actual reference waveform signal SO(t) contained in the received television signal is extracted from a predetermined point in the television signal from the input end chain in FIG. 3 under the timing control of the reference waveform detection section 31c. , is written into the extracted waveform holding means 31a. In order to reduce noise in the extracted waveform, time averaging over a plurality of extraction times is performed by connecting the input terminals of the extracted waveform holding section 31a via the adding section 31b. This received and extracted reference waveform signal S
Due to the influence of transfer characteristics including ghosts, O(t) becomes a distorted waveform with respect to the reference waveform signal So(t) inserted on the transmitting side, as illustrated in FIG. 5(A). Become.

The received reference waveform signal 56(t) is read out from the extracted waveform holding unit 31a, subjected to Fourier transformation in the Fourier transformation unit 32, and is then subjected to a Fourier transformation coefficient group G( jω).

In addition, IG(jω)1 in the figure is the amplitude, and LG(jω
) is the amount of phase rotation.

The dividing unit 34 divides the reference waveform Fourier coefficient R(jω) read from the reference waveform Fourier coefficient holding unit 33 by the Fourier coefficient G(jω) of the corresponding frequency component received from the Fourier transform unit 32. , the transfer characteristic R(jω)/G(jω) of the ghost removal filter is generated.

The correction unit 35 adjusts the frequency characteristic of the transfer characteristic of the ghost removal filter output from the division unit 34 so that removal is not performed in a range exceeding the frequency band of the received television signal, or a specific frequency of the division value is adjusted. Various correction processes are performed, such as appropriately suppressing steep dips and protrusions in , so as not to forcefully equalize them.

The inverse Fourier transform unit 36 performs inverse Fourier transform on the transfer characteristic of the ghost removal filter corrected by the correction unit 35 to generate a tap gain to be given to the removal filter, and supplies the result to the tap gain holding register unit 37. .

The removal filter 38 generates a television signal from which ghosts have been removed from the received television signal based on the tap gain supplied from the tap gain holding register section 37, and supplies this to the output terminal 0.

In the manner described above, a television signal from which ghosts have been removed can be obtained from the output terminal O.

Problems to be Solved by the Invention The conventional ghost removal device described above removes ghosts only from the reference waveform signal that is a part of the received television signal, so it does not remove ghosts at all from the video signal portion other than the reference waveform signal. Not guaranteed.

Since such conventional ghost removal devices set and hold the reference waveform for ghost detection in advance, in the unlikely event that a signal different from the waveform expected by the device as the reference waveform for ghost detection is received by the broadcasting station. When the received television signal is sent from the side, the device mistakenly detects that the difference in the extracted waveform signal is due to a ghost, and forcibly equalizes it to the reference waveform stored in the device.This is because the received television signal is There is a possibility that the signal will be changed to a completely different signal, which will greatly degrade the image quality.

Furthermore, as another example, in the case of a ghost with a very long delay time, the ghost that appears on the reference waveform may not be your own, but may be overlaid by a ghost from an earlier waveform. Even in such cases, ghosts may be erroneously detected and the image quality will deteriorate.

An object of the present invention is to automatically separate the ghost removal output to prevent image quality deterioration when the waveform is degraded due to ghost removal as described above.

Means for Solving the Problems In order to achieve the above object, the ghost removal effect diagnosing device of the present invention uses the television signals before and after ghost removal to detect areas that are not included in the area used for ghost detection. A waveform extracting means for extracting a waveform signal of a region, an ideal waveform holding means for presetting and storing ideal waveform information free of ghosts in this extraction region, and quantitatively determining the degree of similarity between the extracted waveform and the ideal waveform. Correlation calculation means;
The apparatus is equipped with a comparison means for diagnosing the ghost removal effect based on the correlation calculation result, and a switching means for selecting a signal output from the apparatus from the comparison means.

Function: The above-mentioned correlation calculation means quantitatively expresses how similar the waveform before ghost removal is to the ideal waveform. Therefore, by comparing these two values,
It can be determined whether the waveform after removal has been improved relative to the waveform before removal, or whether it has deteriorated.

Further, the waveform extraction means extracts a waveform in an area that is not included in the area used for ghost detection. As a result, since the ghost detection waveform and its surrounding waveforms are different from the extracted waveform and its surrounding waveforms, the respective ghost waveforms are also different. If ghosting has been performed correctly, the entire range of the received television signal will have been deghosted. However, if the delay time of the ghost is longer than a certain level, or if the detected waveform has a shape different from the waveform previously stored in the device, the ghost will be detected incorrectly.In this case, the ghost will be removed in the detection area. However, ghosts are not removed in other areas. Since the extraction region is different from the detection region, waveform information from which ghosts have not been correctly removed is obtained in the extraction region, and it can be seen that ghosts have not been correctly removed by the correlation calculation means and the comparison means.

The above-mentioned switching means outputs a ghost-free television signal when it is determined by the comparison means that ghost removal has been performed correctly, and outputs a ghost-free television signal when it is determined that ghost removal has not been performed correctly. Outputs the signal before removal, that is, the received television signal.

Embodiment FIG. 1 shows a ghost removal device equipped with a ghost removal effect diagnosing device according to the present invention, in which a ghost removal section 1,
It is composed of a pre-removal waveform extraction means 2, an ideal waveform holding means 3, a pre-removal correlation calculation means 4, a post-removal waveform extraction means 5, a pre-removal correlation calculation means 6, a comparison means 7, and a switching means 8.

The received television signal input to the input terminal IN is supplied to one input of the ghost removal section 1, the pre-cancellation waveform extraction means 2, and the switching means 8.

The ghost removal unit 1 can use the conventional technology as it is, and as shown in FIG.
Fourier transform section 32, reference waveform Fourier coefficient holding section 33
, division section 34, correction section 35, inverse Fourier transform section 36, tap gain holding register section 37. It is composed of a removal filter section 38.

The reference waveform signal inserted on the transmission side of the television signal is extracted from a predetermined position in the television signal from the input terminal of the ghost removal section 1 under the timing control of the reference waveform detection section 31c, and the extracted waveform is held. The data is written in the section 31a. In order to reduce noise in the extracted waveform, time averaging over a plurality of extraction times is performed by connecting the input and output terminals of the extracted waveform holding section 31a via the adding section 31b.

On the other hand, the reference waveform Fourier coefficient holding means 33 holds in advance a discrete Fourier coefficient group R(jω) created by Fourier transforming the reference waveform signal inserted on the transmission side of the television signal.

The reference waveform signal extracted by the reference waveform extraction means 31 is
The Fourier transform unit 32 transforms into a discrete Fourier transform coefficient group G(jω).

The dividing unit 34 divides the reference waveform Fourier coefficient R(jω) read from the reference waveform Fourier coefficient holding unit 33 by the Fourier transform coefficient G(jω) of the corresponding frequency component received from the Fourier transform unit 32. , the transfer characteristic R(jω)/G(jω) of the ghost removal filter is generated.

The correction unit 35 adjusts the frequency characteristic of the transfer characteristic of the ghost removal filter output from the division unit 34 to stabilize the removal operation.

The inverse Fourier transform unit 36 performs inverse Fourier transform on the transfer characteristic of the ghost removal filter corrected by the correction unit 35 to generate a tap gain to be given to the removal filter, and supplies the result to the tap gain coefficient holding register unit 37. .

The removal filter 38 generates a television signal from which ghosts have been removed from the received television signal based on the tap gain supplied from the tap gain holding register section 37, and supplies this to the output terminal 0.

The received television signal from which ghosts have been removed by the ghost removal section 1 is supplied to another input of the removed waveform extraction means 5 and the switching means 8.

The pre-removal waveform extraction means 2 uses the waveform signal shown in FIG. 2(a) inserted in the vertical blanking period of the received television signal as the reference waveform for ghost detection by the ghost removal section 1. On the other hand, the waveform near the falling edge of the vertical synchronization signal shown in FIG. 2(b) is used for diagnosing the removal effect.
After being extracted from the received television signal and subjected to time averaging for noise reduction, it is supplied to one input of the removal cylinder correlation calculation means 4.

The ideal waveform holding means 3 previously holds ideal waveform information without ghosts in the waveform for diagnosing the removal effect shown in FIG. Supply to 6.

The removed cylinder correlation calculation means 4 calculates the square error between the waveform signal extracted by the pre-removal waveform extraction means 2 and the waveform information held by the ideal waveform holding means 3, and compares this value with the comparison means 7.
to one input of the

The post-cancellation waveform extraction means 5 performs waveform signal extraction similar to the pre-cancellation waveform extraction means 2 on the received television signal from which the ghost has been removed by the ghost removal section 1, and extracts the waveform signal from the other input of the pre-cancellation correlation calculation means 6. supply to.

The pre-removal correlation calculation means 6 performs a correlation calculation on the waveform signal extracted by the post-removal waveform extraction means 5 using the same procedure as the removed cylinder correlation calculation means 4, and calculates the degree of similarity between the extracted waveform signal and the ideal waveform information. Calculate the value quantitatively and compare it with the means 7
to the other input of the .

The comparing means 7 compares the result of the removed cylinder correlation calculating means 4 with the result of the pre-removal correlation calculating means 6, and controls the switching means 8 based on the result.

In accordance with the output of the comparing means 7, the switching means 8 selects more ideal waveform information after ghost removal if the output value of the pre-removal correlation calculating means 6 is smaller than the output value of the removed cylinder correlation calculating means 4. , the received television signal after ghost removal supplied from the ghost removal unit 1 is supplied to the output terminal OUT. Conversely, removal cylinder correlation calculation means 4
If the output value of the pre-removal correlation calculating means 6 is larger than the output value of , the signal before ghost removal, that is, the received television signal supplied from the input terminal IN, is supplied to the output terminal OUT.

The ghost removal unit 1 can use another ghost removal device that is not related to this embodiment, and even in that case, the configuration of FIG. 1 remains the same. In this embodiment, the second Although the falling edge of the vertical synchronization signal shown in FIG. It is sufficient if it can be maintained at

In the pre-removal correlation calculation means 4 and the post-removal calculation means 6,
Although this embodiment uses a squared error in the correlation calculation procedure, other methods may also be used, for example, an absolute value error or the like may be used.

DETAILED DESCRIPTION OF THE INVENTION As described above, the present invention diagnoses the ghost removal effect in the television signal before and after ghost removal, so that it is possible to avoid erroneously detecting ghosts and deteriorating the received television signal. In such a case, by outputting the original received television signal instead of the degraded signal after ghost removal, it is possible to realize a device in which the received television signal does not deteriorate at least.

Furthermore, since the removal effect is diagnosed using a waveform signal different from the reference waveform signal used for ghost detection in the received television signal, the reference waveform used for ghost detection may differ from the waveform information previously held by the device. This also has the effect of being able to deal with cases where the waveform is different.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a ghost removal effect diagnosing device according to an embodiment of the present invention, FIG. 2 is a schematic diagram of waveforms for explaining the operation of FIG. 1, and FIG. FIGS. 4 and 5, which are block diagrams showing the configuration of a conventional device, are conceptual diagrams for explaining the operation of the circuit shown in FIG. 3. DESCRIPTION OF SYMBOLS 1... Ghost removal part, 2... Waveform extraction means after removal, 3... Ideal waveform holding means, 4... Correlation calculation means before removal, 5... Waveform extraction means after removal, 6... - Pre-removal correlation calculation means, 7... Comparison means, 8... Switching means, 31a...
- Reference waveform holding section, 31b... Addition section, 31c... Reference waveform detection section, 32... Fourier transform section, 33... Reference waveform Fourier coefficient holding section, 34... Division section, 35. . . . Correction section, 36 . . . Inverse Fourier transform section, 37 . . . Tap gain holding register section. 38...Removal filter section. 3rd FI! J

Claims (1)

[Scope of Claims] Pre-removal waveform extraction means for capturing a waveform signal in a region different from a reference waveform signal used for ghost detection from a received television signal before ghost removal; a post-removal waveform extracting means for capturing the waveform extracted by the pre-removal waveform extracting means; an ideal waveform holding means for presetting and storing ideal waveform information of the waveform signal free of ghosts, distortions, etc. in the device; and a waveform extracted by the pre-removal waveform extracting means. signal and
A pre-removal correlation calculation means for performing a correlation calculation with the waveform information read out from the ideal waveform holding means, and a correlation calculation between the waveform signal extracted by the post-removal waveform extraction means and the waveform information read out from the ideal waveform holding means. a comparison means for comparing the results of the post-removal correlation calculation means; and a comparison means for comparing the results of the post-removal correlation calculation means; and selecting either a signal before ghost removal or after ghost removal by the comparison means. What is claimed is: 1. A ghost removal effect diagnostic device, comprising: switching means for outputting a ghost image.