JPH04245869A - Equalizing device for reproduction video signal waveform - Google Patents

Abstract

PURPOSE:To not carry out the waveform equalization of a frequency other than band limiting when a video signal transmitted from a broadcasting station and limited band is recorded and reproduced. CONSTITUTION:A GCR signal detector 1 detects a ghost cancel reference signal from an inputted reproduction signal, and outputs a detection signal when the signal is detected and a non-detection signal when it cannot be detected to a characteristic variable filter 2. It equalizes the waveform of a reproduction signal till the frequency which is transmitted from the broadcasting station and which is band-restricted when the detection signal is inputted, and the waveform of the reproduction signal is equalized with the frequency of a transmission band in the recording/reproducing system of a luminance signal so as to output an output signal when the non-detection signal is inputted.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproduced video signal waveform equalizer in a video signal reproducing apparatus that performs waveform equalization using a variable filter.

0002

[Prior Art] Clear Vision, which began broadcasting in October 1989, has 18
H and 281H have ghost cancellation reference signals (
(hereinafter referred to as the GCR signal) is inserted. This GCR
A conventional reproduced video signal waveform equalization device that performs ghost reduction and waveform equalization on the receiving side using a signal will be described with reference to FIGS. 4 to 6.

First, the standard of the GCR signal is that the signal H (GCR waveform) and the signal L are
(pedestal waveform) is an 8-field sequence,
The signals are inserted in the order of H, L, H, L, L, H, L, H. The rising portion of the GCR waveform is an integral of sinX/X band-limited at 4.2 MHz. A description will be given below based on a block diagram of a ghost cancellation system, which is a conventional waveform equalization device. The symbols in FIG. 5 are represented by a sample value series, and are an input waveform Xk, an output waveform Yk, a reference waveform Rk, and an error waveform Ek. The input waveform Xk and the output waveform Yk are differential (difference) signals of absolute values of AB, which are difference signals between four fields, and are sinX/X waveforms.

The reproduced signal 51 is input to a variable characteristic filter 52 composed of a transversal filter and a four-field difference signal device 53. Characteristic variable filter 52
equalizes the waveform of the input reproduced signal 51 and outputs the output signal 64.
Output. . The 4-field difference signal device 53 takes the difference between the current field and the GCR signal of 4 fields before and outputs it to the differentiator 54. The differentiator 54 differentiates the difference between the GCR signals to generate an input waveform Xk, which is a sinX/X signal.
get.

On the other hand, similarly to the input side, the four-field difference signal device 55 receives the output signal 64 from the variable characteristic filter 52, calculates the difference between the current field and the GCR signal of four fields before, and outputs the difference to the differentiator 56. The differentiator 56 outputs an output waveform Yk, which is a sinX/X signal obtained by differentiating the difference between the GCR signals, to the subtracter 58. The subtracter 58 takes the difference between the output waveform Yk and the output Rk of the reference signal source 57 and outputs an error waveform Ek to the ghost detection device 59. The ghost detection device 59 performs calculations from the input waveform Xk and the error waveform Ek, and outputs the calculation results to the tap gain coefficient correction device 60. Tap gain coefficient modification device 60 exchanges data with tap gain coefficient memory 62 and replaces old tap gain coefficients in tap gain coefficient memory 62 with new ones. Tap gain coefficient writing device 63
writes the tap gain coefficient from the tap gain coefficient memory 62 into the variable characteristic filter 52 and changes the characteristic of the variable characteristic filter 52.

[0006] Through the above control loop, ghost removal,
Waveform equalization is being performed. Note that the reference signal is s of the GCR waveform.
4.2MHz sinX/, which is the same as the inX/X band limit.
It is an X waveform, and only the transmitted video band is waveform-equalized. Next, the operation of the reproduced video signal waveform equalization device configured as described above will be explained.

The reproduced signal 51 is supplied to a variable characteristic filter 52 and a tap coefficient calculation device 61. The variable characteristic filter 52 performs waveform equalization using the written tap gain coefficient and outputs an output signal 64. The tap gain coefficient calculation device 61 calculates a tap gain coefficient from the signals from the reproduced signal 51 and the output signal 64 and the stored tap gain coefficient from the tap gain coefficient memory 62, writes it into the tap gain coefficient memory 62, Gain coefficient writing device 63
writes the tap gain coefficient stored in the tap gain coefficient memory 62 to the variable characteristic filter 52.

[0008] When considering waveform equalization of a video signal recording/reproducing device, the waveform of the transmission band of this reproducing device is equalized. Taking the luminance signal transmission system of an S-VHS VTR as an example, the luminance signal is a low carrier FM recording,
Its carrier frequency is from 5.4 MHz to 7.0 MHz. Therefore, since the transmission band for recording and reproduction of an S-VHS system VTR is about 5 MHz, when waveform equalization is performed, the waveform is equalized in the 5 MHz band. That is, for the frequency amplitude characteristic of the recording and reproducing system of the luminance signal of the S-VHS VTR shown in FIG. 6(a), the band up to about 5 MHz can be changed using the variable characteristic filter having the characteristic shown in FIG. 6(b). I am letting it pass.

[0009] Now, the 4.2MH signal sent from the broadcasting station
When recording a video signal subject to z-band restriction, S-VH
Although a 5 MHz band is passed through waveform equalization in the recording/reproducing system of an S-scheme VTR, the band of the actually recorded video signal is 4.2 MHz, and frequency components above 4.2 MHz are noise.

[0010] In this way, the 4.
When a video signal subject to a 2 MHz band restriction is recorded and reproduced, there is a problem in that if waveform equalization is performed with the characteristics shown in FIG. 6(b), the noise component increases and the S/N ratio deteriorates.

[0011]

[Problems to be Solved by the Invention] As described above, in conventional devices, such as S-VHS VTRs, the transmission band in the luminance signal recording and reproducing system is about 5 MHz, and the video sent from the broadcasting station is In waveform equalization when the signal band is wider than 4.2 MHz, the recorded video signal band is 4.2 MHz.
In the case of Hz, there is a problem in that frequency components outside the band may be passed or increased, resulting in poor S/N ratio. The present invention aims to eliminate the drawbacks of the prior art as described above, and to band-limit the frequency components outside the video signal band when it is determined that the frequency components outside the video signal band are being passed or increased. It is something. [Structure of the invention]

0012

[Means for Solving the Problems] In order to achieve the above object, the present invention includes ghost cancellation reference signal detection means for detecting a ghost cancellation reference signal from an input reproduction signal and outputting a detection signal; waveform equalization means for equalizing the waveform of the reproduced signal using the detection signal and outputting the same, the waveform equalization means limiting the waveform equalization means to a first frequency band when the detection signal indicates that the ghost cancellation reference signal is included; Provided is a reproduced video signal waveform equalization device characterized in that the waveform equalization is performed by limiting the waveform equalization to a second frequency band when the detection signal indicates that the ghost cancellation reference signal is not included. .

[0013]

[Operation] In the device configured as described above, when a GCR signal is detected in the reproduced signal when performing waveform equalization of the reproduced signal, the band of the recorded video signal is 4.2.
Since it is MHz, the variable characteristic filter is set to 4.2MHz during playback.
Waveform equalization is performed by limiting the band to below z, so 4.2MH
It is possible to prevent noise components of z or higher from passing through or increasing, thereby preventing deterioration of the S/N ratio.

[0014]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 4. First example

In FIG. 1, a reproduced signal 3 is detected by a GCR signal detector 1.
and the variable characteristic filter 2. When a GCR signal is included in the reproduced signal 3, the GCR signal detector 1 outputs a detection signal indicating that a GCR signal is included in the characteristic variable filter 2, and when a GCR signal is not included, the characteristic variable detector 1 outputs a detection signal indicating that a GCR signal is included in the variable characteristic filter 2. The filter 2 outputs a non-detection signal indicating that no GCR signal is present.

The characteristic variable filter 2 is the GCR signal detector 1
If the signal from is a detection signal, the cutoff is 4.2M.
The reproduction signal 3 is switched to a 4.2 MHz low-pass filter (hereinafter referred to as LPF) characteristic and becomes an output signal 4 through the 4.2 MHz LPF. Moreover, the signal from the GCR signal detector 1 is
In the case of a non-detected signal, the characteristics are switched to a wideband filter, and the reproduced signal 3 passes through the wideband filter and becomes an output signal 4. Next, the operation of the thus configured reproduced video signal waveform equalization device will be explained.

A reproduced signal 3 is input to the GCR signal detector 1, and when a GCR signal is detected, a detected signal is transmitted, and when a GCR signal is not detected, a non-detected signal is transmitted to a characteristic variable filter 2.
Output to. The characteristic variable filter 2 is the GCR signal detector 1
If the signal from the output signal is a detected signal, the reproduced signal is waveform-equalized so as not to equalize the waveform outside the band of the reproduced signal containing the GCR signal, and if it is a non-detected signal, the output signal 4 is switched to wideband filter characteristics. Output. Second Embodiment A concrete explanation will be given by taking an S-VHS type VTR as an example.

The reproduced luminance signal 5 in FIG. 2 is supplied to a V counter 6, a level detection device 8, and a variable characteristic filter 14. The V counter 6 counts the number of vertical lines of the reproduced luminance signal and outputs a signal indicating the counted number to the insertion position detection device 7. In response to the signal from the V counter 6, the insertion position detection device 7 outputs check signals to the level detection device 8 and the 8-field sequence check device 9 at 18H and 281H. When the check signal is input from the insertion position detecting device 7, the level detecting device 8 detects the detected signals in 8 fields such that the GCR waveform is “H” and the pedestal waveform is “L” depending on the voltage level of the reproduced luminance signal 5. Output to the sequence check device 9. The 8-field sequence check device 9 compares the detected signal with the pattern of the GCR signal for 8 fields to see if it is an 8-field sequence of the GCR signal, and if it is detected that the GCR signal is inserted, the switch 10 changes the tap gain. A signal for selecting the coefficient memory 12 is output, and if it is not detected that the GCR signal is inserted, the switch 10
outputs a signal for selecting the tap gain coefficient memory 11. The tap gain coefficient memory 11 has a waveform equalization band of 5MHz.
tap gain coefficients are stored and output to the switch 10. The tap gain coefficient memory 12 stores a tap gain coefficient for band-limiting the waveform equalization band to 4.2 MHz, and outputs it to the switch 10.

The switch 10 switches the signals from the tap gain coefficient memories 11 and 12 in response to a control signal from the 8-field sequence check device 9 and outputs the signals to the tap gain coefficient writing device 13. Tap gain coefficient writing device 1
3 writes the tap gain coefficient from the memory selected by the switch 10 into the variable characteristic filter 14. The variable characteristic filter 14 performs waveform equalization using the tap gain coefficient written by the tap gain coefficient writing device 13 and outputs an output luminance signal 15. Next, the operation of the thus configured reproduced video signal waveform equalization device will be described.

When the GCR signal is not included in the reproduced luminance signal, the GCR signal detection section 16 causes the switch 10 to select the tap gain coefficient memory 11 and writes the tap gain coefficient to the characteristic variable filter via the tap gain coefficient writing device 13. , the characteristic variable filter performs waveform equalization on the reproduced luminance signal in a 5 MHz band and outputs it. In addition, GC is added to the reproduced luminance signal.
When the R signal is input, the GCR signal detection unit 16 causes the switch 10 to select the tap gain coefficient memory 12, writes the tap gain coefficient to the variable characteristic filter via the tap gain coefficient writing device 13, and the variable characteristic filter receives the GCR signal. Waveform equalization is performed in a band up to 4.2 MHz so that waveform equalization is not performed outside the reproduced brightness signal band containing , and an output brightness signal 15 is output. Third embodiment

In FIG. 3, the reproduced luminance signal 17 is supplied to a V counter 18, a level detection device 20, and a characteristic variable filter 24. The V counter 18 counts the number of vertical lines of the reproduced luminance signal 17 and outputs the counted number to the insertion position detection device 19. The insertion position detection device 19 is a V counter 1
18H and 2 by the signal indicating the count number from 8
At the 81st H, the check signal is detected by the level detection devices 20 and 4.
It is output to the field difference check device 21. When the check signal is input from the insertion position detecting device 19, the level detecting device 20 detects the GC based on the voltage level of the reproduced luminance signal 17.
The R waveform is detected as "H" and the pedestal waveform is detected as "L" and outputted to the 4-field difference check device 21. Then, the 4-field difference check device 21 detects the level detecting device 20 according to the timing of the insertion position detecting device 19.
If a signal pattern in which one of the current field and the previous four fields is "H" and the other is "L" is detected over 8 fields, a detection signal indicating the detection of a GCR signal is transmitted. If it is not detected over eight fields, a non-detection signal indicating non-detection of the GCR signal is output to the switch 27.

[0022] The tap gain coefficient memory 22 has a band of 5 MH.
The tap gain coefficient of z is written and output to the tap gain coefficient writing device 23. Tap gain coefficient writing device 23 reads the tap gain coefficient from tap gain coefficient memory 22 and writes it into variable characteristic filter 24 . The characteristic variable filter 24 performs waveform equalization on the reproduced luminance signal 17 according to the written tap gain coefficient, and passes the waveform equalized signal to a low-pass filter 25 (hereinafter referred to as LPF 25) and a DE.
Output to LAY26. The LPF 25 limits the frequency band of the waveform equalized signal to 4.2 MHz and outputs it to the switch 27 . DELAY26 sends the waveform equalized signal to LPF25
It is output to switch 27 with a delay of the same amount of time as it passes through.

The switch 27 selects the LPF 25 side when a detection signal indicating the detection of a GCR signal is input from the 4-field difference check device 21, and a non-detection signal indicating non-detection of the GCR signal is input from the 4-field difference check device 21. is input, the DELAY 26 side is selected and the output luminance signal 28 is output. Next, the operation of the thus configured reproduced video signal waveform equalization device will be described.

The reproduced luminance signal 17 is transmitted to the GCR signal detection section 30.
and is supplied to the waveform equalization section 29. The GCR signal detection section 30 detects whether a GCR signal is included in the reproduced luminance signal 17 and outputs the detected signal to the switch 27. The tap gain coefficient writing device 23 is the tap gain coefficient memory 2
2, the tap gain coefficient of the frequency band 5 MHz is read out and written into the waveform equalization section 29. The waveform equalizer 29 performs waveform equalization using the tap gain coefficient from the tap gain coefficient writing device 23 and sends the waveform equalized signal whose band is limited to 4.2 MHz and the waveform equalized signal whose band is not limited to the switch 27. Output.

When the signal from the GCR signal detection section 30 is a signal indicating that a GCR signal has been detected, the switch 27 is switched to 4.
．． Select the waveform equalized signal whose band is limited to 2MHz, and apply it to the GC.
If the signal from the R signal detection unit 30 is a signal indicating that no GCR signal has been detected, a waveform equalized signal without band limitation is selected and output luminance signal 28 is output.

[0026]

According to the present invention, when a GCR signal is searched for in the reproduced signal during waveform equalization of the reproduced signal, the band of the variable characteristic filter is the recorded video band of 4.2.
Since the band is limited to MHz, even if the variable filter originally has a correction characteristic that boosts the band above 4.2 MHz, it will correct the actual video band up to 4.2 MHz and eliminate noise components above 4.2 MHz. can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a reproduced video signal waveform equalization device of the present invention.

FIG. 2 is a block diagram of another embodiment of the reproduced video signal waveform equalization device of the present invention.

FIG. 3 is a block diagram of another embodiment of the reproduced video signal waveform equalization device of the present invention.

[Figure 4] GCR of ghost cancellation reference signal
It is a figure which shows a waveform and a pedestal waveform.

FIG. 5 is a block diagram of a conventional reproduced video signal waveform equalization device.

FIG. 6 is a diagram showing the frequency amplitude characteristics of the luminance signal recording and reproducing system of the S-VHS system VTR and the frequency amplitude characteristics of the variable characteristic filter.

[Explanation of symbols]

1 GCR signal detector 2 Variable characteristic filter

Claims (1)

[Claims] 1. Ghost cancellation reference signal detection means for detecting a ghost cancellation reference signal from a reproduction signal reproduced from a recording medium and outputting a detection signal, and a waveform for equalizing the waveform of the reproduction signal with the detection signal and outputting the same. equalizing means, the waveform equalizing means equalizes the waveform by limiting it to a first frequency band when the detection signal indicates that the ghost cancellation reference signal is included; 1. A reproduced video signal waveform equalization device, which performs waveform equalization by limiting the waveform to a second frequency band when it indicates that the signal is not reproduced.