JPH0698203A - Ghost eliminator - Google Patents

Abstract

PURPOSE:To provide a ghost eliminator which can eliminate the sag in a GCR signal and can improve the ghost eliminating function. CONSTITUTION:The level of the horizontal synchronizing signal is detected by a level detector means 5a for a GCR signal including the sag. Then a sag amount estimating means 5b estimates a sag amount based on the level detected by the means 5a. Thus the sag is eliminated by a sag eliminating means 5c. Then a coefficient is set in a transversal filter 3 by a coefficient setting means 5d based on the obtained GCR signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ghost removing device for removing a ghost by using a GCR signal (ghost cancellation reference signal).

[0002]

2. Description of the Related Art First-generation EDTV broadcasting, which aims to improve image quality while maintaining compatibility with current television systems, has been started, and ghost elimination is a major improvement.
In the conventional ghost elimination device, 18H and 2 of each frame
The ghost is removed by extracting the GCR signal contained in 81H, calculating the coefficient data of the transversal filter from this signal, and setting it in the transversal filter.

[0003]

However, the conventional ghost removing apparatus has a drawback that the transversal filter of the ghost removing section may diverge due to erroneous detection of the GCR signal. The cause of this erroneous detection is sag in the analog signal processing system from the detection output of the television signal to the A / D converter. The sag shows a tendency to make one round at the vertical sync rate, and the shape of the sag changes depending on the video signal. Therefore, in the case of a video signal of a moving image, the sag pattern is constantly changing. FIG. 4A shows a 1 V section of a video signal without sag, and FIGS.
Shows different examples of the video signal on which the sag is superimposed. As the sag changes at the vertical sync rate in this way, the sag component is added to the GCR signal.

Further, since the GCR signal is transmitted in a specific horizontal period in a sequence in which it makes a loop of 8 fields, the GCR signal is extracted by performing a predetermined calculation on the signal of 8 fields. FIG. 4D shows the extracted 1H GCR signal when there is no sag. Figure 4
(E) shows the GCR signal after 8-field sequence processing when a signal including sag is input.

When the GCR signal with the sag is directly used for ghost removal as described above, there is a drawback that normal ghost removal cannot be performed and the ghost removal performance deteriorates. Further, in the worst case, the transversal filter diverges, and there is a drawback that the image cannot be reproduced.

The present invention has been made in view of the above conventional problems, and a technical object thereof is to be able to capture a GCR signal without sag.

[0007]

SUMMARY OF THE INVENTION The present invention is a transversal filter for eliminating ghosts in an input video signal, and G
Horizontal sync signal level detecting means for detecting the horizontal sync signal levels before and after the CR signal, and sag amount estimating means for estimating the sag amount in the horizontal period in which the GCR signal is inserted by the detection signal from the horizontal sync signal level detecting means. And a sag removing means for removing the sag amount estimated by the sag amount estimating means from the GCR signal, and a GC removed by the sag removing means.
Coefficient setting means for setting the coefficient value of the transversal filter from the R signal.

[0008]

According to the present invention having such features, the GC
The sag amount is estimated from the horizontal synchronizing signal levels before and after the R signal, and the estimated sag amount is removed from the GCR to extract a sag-free GCR signal. And GCR
Ghosts are removed by setting the coefficients of the transversal filter based on the signal.

[0009]

1 is a block diagram showing the structure of a ghost removing apparatus according to an embodiment of the present invention. In the figure, an input terminal 1 is a terminal for inputting a video signal, and is an A / D
The converter 2 is connected. The A / D converter 2 converts an input video signal into a digital signal, and its output is given to the transversal filter 3 and the waveform memory 4. The waveform memory 4 is a memory that holds A / D-converted data for several fields, and its read signal is given to the CPU 5. As will be described later, the CPU 5 detects the level of the horizontal synchronizing signal, estimates the sag amount to remove the sag from the GCR signal, and calculates the coefficient of the transversal filter 3 from the GCR signal. The transversal filter 3 removes a ghost based on the coefficient value set in this way, and its output is D
It is converted into an analog signal by the / A converter 6. The output is fed back to the CPU 5 via the waveform memory 7. The terminal 8 is an output terminal for outputting a video signal converted into an analog signal.

Next, the operation of this embodiment will be described. FIG. 2 is a diagram showing a video signal of a GCR signal including sag in one horizontal scanning period. As shown in this figure, one horizontal scanning period is sufficiently shorter than the vertical period, so the influence of sag in the horizontal scanning period can be approximated by a straight line. FIG. 2B shows a pedestal of a GCR signal having a sag having a slope of a / b, where the horizontal scanning period is b. Therefore, by removing the influence of this sag, the GCR signal without sag shown in FIG. 2C can be obtained.

When a video signal is input to the input terminal 1, the waveform is input to the waveform memory 4 via the A / D converter 2. Then, the CPU 5 fetches the A / D converted values of the horizontal synchronizing signals before and after 18H and 281H including the GCR signal in the flowchart shown in FIG. 3 (step 11). Then, the procedure proceeds to step 12, where the levels of the horizontal synchronizing signal c before and after the GCR signal are detected, and step 13
The slope a / b is calculated at. Then, the process proceeds to step 14, and the sag amount is detected by linearly interpolating from this inclination. This linearly interpolated sag amount is shown as shown in FIG. Therefore, the waveform memory 4 shown in FIG.
In step 15, the sag amount which is linearly interpolated from the GCR signal held in is removed. By doing so, a signal without sag is equivalently obtained as shown in FIG.

A GCR signal is extracted from the thus obtained GCR signal by an 8-field sequence. Where G
The CR signal corresponds to the WRB signal shown in FIG. 2C and the CR signal shown in FIG.
The 0 pedestal signal shown in and are transmitted over 8 fields. That is, WRB signal → 0 pedestal signal → W
RB signal → 0 pedestal signal → 0 pedestal signal → WR
The B signal, the 0 pedestal signal, and the WRB signal are sequentially overlapped in the same horizontal scanning period in a sequence of one cycle of eight fields. Therefore, the GCR signal is obtained by performing the calculation represented by the following equation on the signals in the horizontal scanning period of these fields. However, F _n (n = 1 to 8) represents a signal in the horizontal scanning period in which the GCR signal of the nth field is included.

## EQU1 ## F = 1/4 {(F ₁ −F ₅ ) + (F ₆ −F ₂ ) + (F ₃ −F ₇ ) + (F ₈ −F ₄ )}

The GCR signal obtained after the processing of the 8-field sequence is completed is shown in FIG. 2 (e). After that, the coefficient of the transversal filter 3 is calculated in step 17, and this value is set in the transversal filter 3 in step 18.

Here, the CPU 5 achieves the function of the horizontal synchronizing signal level detecting means 5a for detecting the level of the horizontal synchronizing signal before and after the GCR signal in steps 11 and 12. Further, in steps 13 and 14, the function of the sub amount estimating means 5b for estimating the sub amount based on the level of the horizontal synchronizing signal is achieved. Further, in step 15, sub-removing means 5c for removing the sub-quantity from the original GCR signal.
The function of the coefficient setting means 5d for calculating and outputting the coefficient of the transversal filter in steps 17 and 18 is achieved.

The transversal filter 3 operates according to the coefficient thus set. Then, the ghost can be accurately removed from the sag-free GCR signal.

[0016]

As described in detail above, according to the present invention, the coefficient of the transversal filter is set by detecting the sag amount based on the horizontal synchronizing signal and calculating the GCR signal. Therefore, it is possible to realize a ghost removing device that can prevent phenomena such as divergence.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a ghost removing device according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing a ghost signal of the ghost removing device according to the embodiment of the present invention.

FIG. 3 is a flowchart showing the operation of this embodiment.

FIG. 4 is a waveform diagram showing a relationship between sag and a video signal.

[Explanation of symbols]

 2 A / D converter 3 Transversal filter 4, 7 Waveform memory 5 CPU 5a Horizontal sync signal level detecting means 5b Sag amount estimating means 5c Sag removing means 5d Coefficient setting means

Claims (1)

[Claims] 1. A transversal filter for removing a ghost of an input video signal, a horizontal synchronizing signal level detecting means for detecting a horizontal synchronizing signal level before and after a GCR signal, and a detection signal from the horizontal synchronizing signal level detecting means. The sag amount estimating means for estimating the sag amount in the horizontal period in which the GCR signal is inserted, and the sag amount estimated by the sag amount estimating means are set to GCR.
A ghost removing apparatus comprising: a sag removing unit that removes the signal, and a coefficient setting unit that sets a coefficient value of the transversal filter from the GCR signal removed by the sag removing unit.