JPH03253178A - Waveform equalizer - Google Patents

Abstract

PURPOSE:To prevent high frequency over-emphasis even when a video signal affected by jitter is inputted by correcting the characteristic of an internal reference signal based on jitter quantity detected by a jitter detection circuit. CONSTITUTION:The quantity of jitter included in an input video signal is detected by a jitter detection circuit 16. The high frequency component of the reference signal is suppressed by correcting the frequency amplitude characteristic in the process of waveform equalization when the effect of jitter is received. A characteristic variable filter 15 based on the quantity of jitter detected by the jitter detection circuit 16 corrects the frequency characteristic of the internal reference signal from a reference signal source 11 by the high frequency suppression component received by a detected GCR(ghost cancel reference) signal. Thus, the over-emphasis of the high frequency component due to the waveform equalization by the arithmetic processing between the detected reference signal and the internal reference signal is prevented.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a waveform equalization device, and in particular, to waveform equalization of a video signal containing jitter, such as a playback signal from a recording/playback device. The present invention relates to a preferred waveform equalization device.

(Prior art) In recent years, there has been a demand for higher image quality in television broadcasting, and television broadcasting using the EDTV system has been started since October 1989. A GCR (Ghost Cancellation Reference) signal is superimposed on the television signal and transmitted as a reference signal.In other words, in the vertical blanking section 188 and 2810, as shown in FIG. The sinx/x integral waveform shown in (hereinafter referred to as W
An RB (Wide Reverse Bar) waveform) or a pedestal waveform shown in FIG. 6(b) is inserted. The WRB waveform and the pedestal waveform are inserted in an 8-field sequence, with the WR8 waveform inserted in the 1.3.6°8 field and the pedestal waveform inserted in the 2nd°4.5.7 field. . This GCR
Waveform equalization devices that perform ghost removal and waveform equalization using signals have been commercialized.

FIG. 7 is a block diagram showing a conventional waveform equalization device employed in television tuners, receivers, etc.

A video signal that has been subjected to ghost interference, waveform distortion, etc. is input to the input terminal 1. A GCR signal is inserted into this video signal. The input video signal is input to a transversal filter (hereinafter referred to as TF) 2 that performs waveform equalization, and is also input to a four-field difference signal circuit 3. The TF 2 has a delay device, a multiplier, an adder, and a subtracter (not shown), and the gain of each multiplier is controlled by the tap coefficient given from the tap gain memory 4 to equalize the waveform of the input video signal. . 4-field difference signal circuit 3
For example, subtracts the WR8 waveform of the first field and the pedestal waveform of the fifth field and supplies the result to the differentiating circuit 5. The differential (difference) signal from the differentiating circuit 5 is given as an input waveform (xk) to the ghost detection circuit 6. On the other hand, the video output from TF2 is output to the output terminal 7, and the 4-field difference signal circuit 8 The output of the four-field difference signal circuit 8 is differentiated by a differentiating circuit 9 and is applied as an output waveform (yk) to a subtracting circuit 10.The subtracting circuit 10 converts the reference waveform (y
k) and the output waveform (Vk), and calculate the error waveform (
ek) is output to the ghost detection circuit 6.

The ghost detection circuit 6 detects the input waveform (xk) and the error waveform (
ek ), and correct the tap coefficient given to TF2 so that the error waveform (ek) converges to O. The calculation result is given to the tap gain correction circuit 12,
The tap gain correction circuit 12 sends and receives data to and from the tap gain memory 4, and updates the tap coefficients of the tap gain memory 4 at predetermined intervals. A tap coefficient is given to the multiplier from the tap gain memory 4, the characteristics of TF2 are changed, and ghost removal waveform equalization is performed.

Incidentally, a video signal containing jitter may be input to the input terminal 1. Figure 8 shows the frequency of the double wheels and the gain on the vertical axis, and the s obtained from the differentiator circuit 5°9.
It is a graph which shows the spectrum of an inx/x waveform. The mA spectrum shown by the solid line in FIG. 8 shows an example not affected by jitter, and the B spectrum shown by the broken line shows an example affected by jitter. When a video signal affected by jitter is input, the spectra of the input waveform (xk) and output waveform (yk) are differentiated by the differentiation circuit 5.9, as shown in spectrum B in Figure 8. The high range becomes suppressed. As mentioned above, the ghost detection circuit 6 corrects the tap coefficients so that the error waveform (ek) becomes 0, and the high frequencies of the input and output waveforms are suppressed, so the output of the transversal filter 2 is The high range becomes over-emphasized. This high-frequency overemphasis causes ringing, lowering the S/N ratio and deteriorating image quality.

(Problems to be Solved by the Invention) As described above, in the conventional waveform equalization device described above,
When a video signal affected by jitter is input, there is a problem in that the high frequency range is overemphasized and the image quality deteriorates.

The present invention has been made in view of such problems, and includes:
It is an object of the present invention to provide a waveform equalization device that can prevent high-frequency overemphasis and obtain a good image even when a video signal affected by jitter is input.

[Structure of the Invention] (Means for Solving the Problems) A waveform equalization device according to the present invention includes a reference signal source and a reference signal extraction circuit, and a reference signal extracted by the reference signal extraction circuit from an input video signal. In a waveform equalization device that equalizes the waveform of an input video signal based on arithmetic processing of the input video signal and an internal reference signal from the reference signal source, the input video signal is equalized by a synchronization signal obtained by separating and extracting from the input video signal. a jitter detection circuit that detects the amount of jitter included; and a frequency characteristic correction means that corrects the frequency characteristics of the reference signal from the reference signal extraction circuit or the internal reference signal based on the amount of jitter detected by the jitter detection circuit. It is equipped with

(Operation) In the present invention, the jitter amount included in the input video signal is detected by the jitter detection circuit.

If the reference signal is affected by jitter, the frequency amplitude characteristics are corrected in the process of waveform equalization, thereby suppressing the high frequency range. The frequency characteristic correction means uses the detection GCR based on the amount of jitter detected by the jitter detection circuit.
Only the high-frequency suppression valve that receives the signal corrects the frequency characteristics of the detection reference signal or internal reference signal. This prevents high frequencies from being overemphasized due to waveform equalization through arithmetic processing of the detection reference signal and the internal reference signal.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings. FIG. 1 is a block diagram showing an embodiment of a waveform equalization device according to the present invention. In FIG. 1, the same components as in FIG. 7 are given the same reference numerals.

An input terminal 1 receives a reproduced video signal on which a GCR signal is superimposed. TF2.4 field difference signal circuit 3, 8
, the tap gain memory 4, the differentiating circuit 5.9, the ghost detection circuit 6, the subtraction circuit 10, the reference signal 5 source 11, and the tap gain correction circuit 12 are the same as the conventional ones. That is,
TF2 has a delay device, a multiplier, an adder, and a subtracter (not shown), and the gain of each multiplier is controlled by a tap coefficient to equalize the waveform of the input video signal. The 4-field difference signal circuits 3 and 8 are GCRs before and after the 4-field.
The signals, that is, the WR8 waveform and the pedestal waveform are subtracted and outputted to differentiating circuits 5.9, respectively.

The differentiator circuit 5.9 differentiates the signal from the four-field difference signal circuit 3.8, thereby outputting a signal with an s r nx/x waveform. The differential signal from the differentiator circuit 5 has an input waveform (
The differential signal from the differentiator circuit 9 is applied to the subtraction circuit 10 as an output waveform (yk).

In this embodiment, the reference waveform (
γk) is applied to the subtraction circuit 10 via the variable characteristic filter 15. The variable characteristic filter 15 receives tap coefficients from a jitter detection circuit 16, which will be described later, and generates a reference waveform (γ
k) The frequency characteristics are corrected.

The subtraction circuit 10 determines the error between the reference waveform corrected by the characteristic variable filter 15 and the output waveform (yk), and outputs the error waveform (ek) to the ghost detection circuit 6. Ghost detection circuit 6 detects input waveform (xk) and error waveform (ek)
The error waveform (ek) converges and O
Correct the tap coefficient so that The calculation result of the ghost detection circuit 6 is given to the tap gain correction circuit 12. The tap gain correction circuit 12 sends and receives data to and from the tap gain memory 4 to update the tap coefficients in the tap gain memory 4. Tap gain memory 4 provides tap coefficients to TF2.

On the other hand, the video signal input via the input terminal 1 is also provided to the jitter detection circuit 16. FIG. 2 is a block diagram showing a specific configuration of the jitter detection circuit 16.

A video signal from input terminal 1 is applied to sync separation circuit 20 . A synchronization separation circuit 20 separates a horizontal synchronization signal from the video signal and supplies it to a time interval measurement circuit 21 . The time interval measurement circuit 21 determines the periodic fluctuation of the horizontal synchronization signal due to the influence of jitter from the output of the synchronization separation circuit 20. The standard deviation calculation circuit 22 statistically processes the data of n integer values from the time interval measurement circuit 21 to obtain a standard deviation. This standard deviation value is given to the frequency characteristic calculation circuit 23. The frequency characteristic calculation circuit 23 calculates the frequency characteristic due to jitter, that is, the high frequency reduction characteristic from the standard deviation value. The data on this high-frequency reduction characteristic is given to the tap coefficient calculation circuit 24, and the tap coefficient calculation circuit 24 calculates a tap coefficient for correcting the reference waveform (γk) from the reference signal source 11 according to the high-frequency reduction characteristic. . The tap coefficient output circuit 25 gives this tap coefficient to the variable characteristic filter 15 via the output terminal 26,
The characteristics of the variable characteristic filter 15 are determined.

Next, the operation of the waveform equalization device configured as described above will be explained.

The reproduced video signal of the VTR is sent to TF2 via input terminal 1.
is input. The gain of the multiplier in TF2 is adjusted by the tap coefficient to perform waveform equalization and output a video signal to the output terminal 7. That is, as in the prior art, the input and output video signals are each inputted into four fields by the four-field difference signal circuit 3.8.
The WRB waveform before and after the field and the pedestal waveform are subtracted, and further, by the differentiating circuit 5.9, s inx/x
The input waveform (xk) and the output waveform (xk) are converted into waveforms.
yk). On the other hand, the video signal is also given to the jitter detection circuit 16. Jitter detection circuit 16
measures the periodic variation of the horizontal synchronizing signal due to jitter to determine the standard deviation, determines the frequency characteristics based on this standard deviation value, and calculates the tap coefficient. This tap coefficient is given to the characteristic variable filter 15. Characteristic variable filter 15
corrects the frequency characteristics of the reference waveform (γk) based on the tap coefficients and supplies it to the subtraction circuit 10. As a result, the subtraction circuit 10 is provided with a reference waveform exhibiting characteristics similar to the frequency characteristics of the sinx/x waveform affected by jitter.

The subtraction circuit 10 obtains an error waveform (ek) from the reference waveform whose frequency characteristics have been corrected from the variable characteristic filter 15 and the output waveform (yk), and supplies it to the ghost detection circuit 6.

The ghost detection circuit 6 detects the input waveform (Xk) and the error waveform (e
By performing a correlation calculation with the error waveform (ek
) outputs the calculation result that converges. In this way, the tap gain coefficient correction circuit 12 sequentially corrects the tap coefficients, and TF2 performs waveform equalization of the input video signal.

In this way, in this embodiment, the characteristic variable filter 1
5 corrects the frequency characteristics of the reference waveform (γk) from the reference signal 1; ill according to the high-frequency reduction characteristics due to jitter and supplies it to the subtraction circuit 10, and the transversal filter 2 corrects the high-frequency overemphasis. It prevents you from doing it.

FIG. 3 is a block diagram showing another embodiment, and FIG. 4 is a block diagram showing a specific configuration of the jitter detection circuit in FIG. 3. In FIG. 4, the same components as in FIG. 2 are given the same reference numerals, and their explanations will be omitted.

The waveform equalization section 30 surrounded by the broken line in FIG. 3 has the same configuration as the broken line part in FIG. In this embodiment, a plurality of reference signal sources Ref1. Ref2 ,...Refm(m
is a natural number), and each reference signal source ReN, R
ef2, -, and Refs each output a reference waveform whose high frequency characteristics are corrected according to the amount of jitter. These reference waveforms are applied to the subtraction circuit 1° (see FIG. 1) of the waveform equalizer 3o via the switch 31. The switch 31 selects the reference signal source based on the selection signal from the jitter detection circuit 32. , selectively provides a reference waveform from a selected reference signal source to the subtraction circuit 10.

The configuration of the jitter detection circuit 32 is the same as the jitter detection circuit 1 in FIG.
It is almost the same as 6. That is, the jitter detection circuit 32 includes a synchronization separation circuit 20, a time interval measurement circuit 2L standard deviation calculation circuit 22, a frequency characteristic calculation circuit 23, and a selection signal generation circuit 27. The output of the frequency characteristic calculation circuit 23 is given to a select signal generation circuit 27. The select signal generation circuit 32 outputs a select signal for selecting a reference signal source from the output terminal 28 based on the frequency characteristics indicated by the input data. This results in
The switch 31 is configured to selectively output a reference waveform having characteristics similar to the frequency characteristics of the detected GCR signal (s inx/x waveform).

In the embodiment configured in this manner, the jitter detection circuit 32 determines the high frequency reduction characteristic due to jitter contained in the input video signal, and selects a reference signal source that outputs a reference waveform with characteristics similar to this characteristic. A select signal for this purpose is given to the switch 31. The switch 31 selectively provides the subtraction circuit 10 with a reference waveform from a reference signal source designated by the select signal. Other operations are similar to the embodiment shown in FIG.

It is clear that the same effects as in the embodiment shown in FIG. 1 can be obtained in this embodiment as well.

FIG. 5 is a block diagram showing another embodiment of the present invention.

In FIG. 5, the same components as in FIG. 1 are given the same reference numerals, and their explanation will be omitted.

In this embodiment, the reference waveform (
γk) is applied to the subtraction circuit 10 without correction, and the frequency characteristics of the output signal of the 4-field difference signal circuit 3.8 are corrected. That is, the output of the 4-field difference signal circuit 3 is given to the differentiating circuit 5 via the variable characteristic filter 34, and the output of the 4-field difference signal circuit 8 is given to the differentiating circuit 9 via the variable characteristic filter 35. It is being Characteristics of the variable characteristic filters 34 and 35 are determined by tap coefficients from the jitter detection circuit 36. The jitter detection circuit 36 has the same configuration as the jitter detection circuit 16 shown in FIG. 1, and provides the variable characteristic filters 34 and 35 with tap coefficients based on the amount of jitter contained in the input video signal.

In the embodiment configured in this way, the four-field difference signal circuit 3.
The output signals from 8 are each subjected to frequency correction based on the amount of jitter contained in the input video signal, and then supplied to a differentiating circuit 5.9. Thereby, it is possible to prevent the high frequency range from being overemphasized in TF2.

Note that the variable characteristic filters 34 and 35 are connected to differentiating circuits 5 and 5, respectively.
It is clear that the same operation and effect can be obtained even if it is provided on the output side of 9.

Furthermore, the present invention is not limited to the above embodiments,
For example, in each of the above embodiments, an example has been described in which the application is applied to a waveform equalization device using a sequential calculation method that calculates tap coefficients of a transversal filter in the time domain, but a batch calculation method that calculates tap coefficients of a transversal filter in the frequency domain. It can also be applied to other waveform equalizers.

[Effects of the Invention] As explained above, according to the present invention, even when the input video signal is affected by jitter, it is possible to prevent high frequencies from being overemphasized and obtain a video with good image quality. It has the effect of being able to

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the waveform equalization device according to the present invention, FIG. 2 is a block diagram showing the configuration of the jitter detection circuit in FIG. 1, and FIG. 3 is a block diagram showing another embodiment of the present invention. A block diagram showing an example, FIG. 4 is a block diagram showing the configuration of the jitter detection circuit in FIG. 3, FIG. 5 is a block diagram showing another embodiment of the present invention, and FIG. 6 is a waveform showing the GCR signal. 7 is a block diagram of a conventional waveform equalizer, and FIG. 8 is a graph for explaining the problems of the conventional example. DESCRIPTION OF SYMBOLS 1... Input terminal, 11... Reference signal source, 15... Variable characteristic filter, 16... Jitter detection circuit. Figure 1 Figure 2 = Horsefly

Claims (1)

[Scope of Claims] The reference signal extraction circuit includes a reference signal source and a reference signal extraction circuit, and the reference signal extraction circuit receives an input signal based on arithmetic processing of a reference signal extracted from an input video signal and an internal reference signal from the reference signal source. A waveform equalization device that performs waveform equalization of a video signal includes: a jitter detection circuit that detects the amount of jitter contained in the input video signal using a synchronization signal obtained by separating and extracting the input video signal; 1. A waveform equalization device comprising: frequency characteristic correction means for correcting the frequency characteristics of the reference signal from the reference signal extraction circuit or the internal reference signal based on the amount of jitter.