JPH0349480A - Ghost elimination device - Google Patents

Abstract

PURPOSE:To sufficiently enhance the ghost elimination capability by controlling a clock phase based on the result of comparison of data at both sides of a peak point to apply sampling nearly at a peak point of a reference signal for ghost elimination at all times. CONSTITUTION:The device is provided with means 7, 13 detecting a peak point of an extracted reference signal, a means 14 comparing data at both sides of the peak point, and means 12, 15 controlling the phase of the sampling clock to convert the reference analog signal into a digital signal based on the result of comparison. In this case, the peak point is sampled by comparing data at both sides of the peak point so as to recognize whether or not sampling of a reference signal GCR for ghost elimination is implemented. That is, as a point closer to the peak point is sampled, a difference of data at both sides is decreased more. Since the phase of a sampling clock is controlled based on the result of comparison, the sampling of the reference signal GCR for ghost elimination is sampled so as to sample the peak point surely.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has a method in which a reference signal for ghost removal is inserted into a video signal in advance, and a ghost signal included in the video signal is removed based on this reference signal. Use the ghost removal device that you used. [Prior Art] For example, when radio waves emitted from a transmitting antenna hit a building or other structure or mountain and are reflected, reaching the receiving antenna, a ghost signal is included in the video signal and appears as a ghost in the image. , which degrades image quality. Currently, in view of the trend toward higher image quality, consideration is being given to having broadcasting stations insert a ghost removal reference signal GCR into video signals before transmitting them, so that ghost signals can be easily removed on the receiving side. As this reference signal GCR for ghost removal, a sin(x)/r pulse as shown in FIG. 3A,
A sin(+r)/x bar as shown in Figure B is used. The sin(x)/x bar is converted into a sin(x)/r pulse by differentiation before use.

Further, as described above, a ghost removal device has been proposed that uses a transversal filter to remove a ghost signal contained in a video signal. FIG. 4 shows an example.

In the same figure, input terminal 1 has, for example, a video detection circuit (
(not shown) is supplied, and this video signal SV! ! After being converted into a digital signal by the A/D converter 4, it is supplied to the adder 2. This video signal S
A reference signal GCR for ghost removal is provided between the vertical retrace lines of
, for example, a sin(X>/X pulse is inserted. The output signal of addition B2 is supplied to a transversal filter 3, and the transversal filter 3 compares the time and level with the ghost signal included in the video signal Sv. A ghost-removed signal is formed by adjusting W@ so as to match and inverting the polarity.The tap coefficient of this transversal filter 3 is set as follows.The output signal of the adder 2 is ghost-removed. The reference signal GCR for ghost removal is supplied to the extraction circuit 7 for the reference signal OCR for ghost removal.
Only the portion is extracted and this portion is supplied to the subtracter 8. This subtracter 8 is supplied with a ghost removal reference signal GCR' from a reference waveform generator 9. In this case, the reference waveform generator 9 generates a ghost removal reference signal GCR' using a ROM or the like.

The subtracter 8 outputs an error signal e obtained by subtracting the ghost removal reference signal GCR' from the output signal of the extraction circuit 7, and this error signal e is supplied to the tap coefficient generator 10. In this tap coefficient generating section 10, tap coefficients are calculated based on the error signal e, and thereby the tap coefficients of the transversal filter 3 are set, and the ghost-removed signal as described above is formed.

Further, the ghost-removed signal formed by the transversal filter 3 is supplied to the adder 2, and the ghost-removed signal is subtracted from the video signal Sv.

As a result, the adder 2 outputs the video signal SV' from which the ghost signal has been removed, and this video signal Sv' is
The signal is converted into an analog signal by the A converter l6 and then supplied to the output terminal 11.

Note that the output signal of the D/A converter 16 is supplied to the color burst extraction circuit 5, and the extracted color burst is as follows.
For example, it is supplied as a reference signal to the clock generation circuit 6 composed of a PLL. A clock CLK synchronized with the color burst is generated from the clock generation circuit 6, and this clock CLK is supplied to the A/D converter 4 as a sampling clock. [Problem 11 to be solved by the invention] As described above, in the example of FIG. signal OC
Ghost signals are removed by waveform equalizing R'.

The ghost removal reference signal GCR' generated by the reference waveform generator 9 is normally written in a ROM or the like as data sampled at peak points, as shown in FIG. 5A. Here, the peak point is
Points to the point of maximum amplitude in the state of sin(z)/z pulse,
This peak point can be considered as a reference point for ghost removal.

Here, there is no problem if the ghost removal reference signal OCR extracted from the video signal Sv is also sampled by the A/D converter 4 so that the peak point is sampled, as shown in FIG. In other words, unless the A/D converter 4 samples the ghost removal reference signal GCR so that approximately the peak point is sampled, sufficient ghost removal ability cannot be obtained. However, although the clock CLK supplied to the A/D conversion@4 is said to be synchronized with the color burst, the phase relationship between the ghost removal reference signal OCR and the color burst is not managed in any way.

Therefore, the ghost removal reference signal OCR extracted from the video signal Sv is not necessarily sampled by the A/D converter 4 so that the peak point is sampled. For example, FIG. 5B, C. There is also a possibility that it will be sampled as shown in D. In times like this,
The ability to eliminate ghost signals is significantly degraded.

Therefore, it is an object of the present invention to provide a ghost removal device that can always exhibit sufficient removal ability.

[Means for Solving the Problems] The present invention extracts the reference signal for ghost removal inserted into the input video signal No. 1118 in the form of a digital signal, and removes the ghost contained in the input video signal based on this base a signal. This assumes a ghost removal device that removes the signal. A means for detecting the peak point of the reference signal to be extracted, a means for comparing data on both sides of this peak point, and a sampling clock for converting the reference signal from an analog signal to a digital signal based on the comparison result. and means for controlling the phase of the phase.

[Operation] By comparing the data on both sides of the peak point, the ghost removal reference signal OCR is set so that the peak point is sampled.
You can see whether sampling is being performed. In other words, the closer the points to the peak point are sampled, the smaller the difference between the data on both sides. In the above configuration, since the phase of the sampling clock is controlled based on the comparison result, the ghost removal reference signal GCR is sampled to ensure that the peak point is sampled. [Embodiment] An embodiment of the present invention will be described below with reference to FIG. In this Figure 1, the 41st! The parts corresponding to l are given the same reference numerals, and detailed explanation thereof will be omitted. In this example, the clock CLK generated by the clock generation circuit 6 is supplied to the clock phase selection circuit l2.
The clock CLK' output from the clock phase selection circuit 12 is supplied to the A/D converter 4 as a sampling clock. This clock phase selection circuit 12 is configured, for example, as shown in FIG. In the figure, the clock CL from the clock generation circuit 6
K is supplied to seven series circuits of 11 extension circuits 121 to 127. The delay time T of each of these delay circuits 121 to 127 is assumed to be 1/8 of the frequency of the clock CLK. The clocks output from the clock CLK% delay circuits 121 to 127 from the clock generation circuit 6 are supplied to a multiplexer 128, respectively. Further, the output signal of the extraction circuit 7 is supplied to a peak point lateral output circuit 13 and a both-side data comparison circuit 14. Then, the detection signal from the peak point detection circuit 13 is supplied to the both-side data comparison circuit 14, and the data on both sides of the peak point are compared, and the comparison result is obtained by, for example, a microprocessor. It is supplied to the controller 16. Multiplexer 1 of this clock phase selection circuit l2
The switching of 28 is performed based on control data SC from the controller 15. In the above configuration, first, l from the controller 15 is
The clock CLK from the clock generation circuit 6 is selected in the multiplexer 12 by the FIin data SC,
This clock CLK is sent to the A/D converter 4 using the clock CLK.
', and at this time, the comparison results from the both-side data comparison circuit 14 are supplied to the controller 15 and stored. Next, the multiplexer 128 selects the clock output from the delay circuit 121 according to the control data SC from the controller 15, and this clock is supplied to the A/D converter 4 as the clock CLK'. The comparison result from controller 15
is supplied to and stored. Thereafter, similarly, in the multiplexer 128, the delay circuits 122 to 12? The clock outputted from the data comparison circuit 14 is selected, and the comparison results from the data comparison circuit 14 on both sides are supplied to the controller 15 and stored therein. After that, control data SC is supplied from the controller 15 to the multiplexer 12B based on the above comparison result,
This multiplexer 12B selects a clock that can sample the point where the difference between the data on both sides of the peak point is the smallest, that is, the point closest to the peak point of the ghost removal reference signal OCR. CLK'. As described above, according to this example, the A/D converter 4 is supplied with a clock CLK' that can sample the point closest to the peak point of the ghost removal reference signal OCR. In other words, A/
In the D conversion B4, sampling is performed so that substantially the peak point of the ghost removal reference signal OCR is always sampled, so that the ghost removal ability can be fully demonstrated. Therefore, by using the ghost removal device of this example, it is possible to obtain a high-quality image from which ghosts have been effectively removed.

Note that in the above embodiment, the clock phase selection circuit l
2 is constructed using seven M extension circuits 121 to 127 having a delay time of 1/8 of the clock CLK, and a multiplexer 128 selects clocks with eight types of phases. However, by configuring the circuit using a large number of delay circuits with a small I1 delay time, it is of course possible to select the clock phase in the multiplexer 128 more precisely.

[Effects of the Invention] As explained above, according to the present invention, the clock phase is determined based on the comparison result of data on both sides of the peak point.
Therefore, sampling is performed so that approximately the peak point of the reference signal for ghost removal is always sampled.
Therefore, the ghost removal ability can be fully demonstrated.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram of a clock phase selection circuit, and v. FIG. 3 is a waveform diagram showing the reference signal for ghost removal, FIG. 4 is a configuration diagram of a conventional example, and FIG. 5 is a waveform diagram showing changes in the reference signal for ghost removal due to changes in the sampling phase. 1・◆・Input terminal 2...Adder 3◆・・Transversal filter 4...A/D converter 6・◆●Clock extraction circuit 7...Ghost removal reference signal extraction circuit 8●・・Subtractor 9...Reference waveform generator 10...Tap coefficient generator 11・◆・Output terminal 12...Clock phase selection circuit 13...Peak point detection circuit 14...Both side data comparison circuit 15 ...Controller 16・●●D/A converter

Claims (1)

[Claims] (1) In a ghost removal device that extracts a reference signal for ghost removal inserted into an input video signal in the form of a digital signal, and removes the ghost signal included in the input video signal based on this reference signal. , means for detecting a peak point of the extracted reference signal;
A ghost characterized by comprising means for comparing data on both sides of the peak point, and means for controlling the phase of a sampling clock for converting the reference signal from an analog signal to a digital signal based on the comparison result. removal device.