JP2916737B2 - Crosstalk removing device for reproduced carrier color signal such as VTR and delay device used therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a PAL system V
The present invention relates to a crosstalk removing device for a reproduced carrier color signal suitable for use in a TR (video tape recorder) and a delay device used therefor.

[0002]

2. Description of the Related Art Generally, video signals are recorded in a home VTR without a guard band. When the signal thus recorded is reproduced, crosstalk from an adjacent track occurs in the reproduced low-frequency conversion color signal. In a PAL / VHS VTR, the phase of the carrier color signal of one track is set to 9
A video signal subjected to PS processing of switching by 0 ° every 1H (one horizontal period) is recorded, and the crosstalk of the reproduced color signal is removed by utilizing the correlation of the PAL color signal every 2H. doing.

FIG. 4A shows an example of such a crosstalk removing device for color signals. FIG.
1A, reference numeral 1 denotes an input terminal to which a reproduced low-frequency conversion color signal is input. This reproduced low-frequency conversion color signal has been subjected to color signal processing for guard bandless recording, for example, the PS processing. The reproduced low-frequency converted chrominance signal input to the input terminal 1 is input to a balanced modulator 2 which is a frequency converter and frequency-converted into a balanced modulated signal, and the PS processing and the like are returned to the original. The balanced modulation signal output from the balanced modulator 2 is input to a band-pass filter (BPF) 3, and only a signal in the vicinity of 4.43 MHz, which is the lower band of the balanced modulation signal, is extracted and becomes a carrier chrominance signal. This carrier chrominance signal contains crosstalk. The carrier color signal including the crosstalk and the carrier color signal
The subtracter 5 subtracts the 2H delayed carrier chrominance signal obtained by passing through the H delay element 4. By this subtraction, PA
The crosstalk from the adjacent track of the reproduced low-frequency conversion color signal is 2H for each 2H in the L-system carrier color signal.
Since the relationship with the previous signal is reversed, a carrier chrominance signal from which crosstalk has been removed is obtained at the output terminal 6.

[0004] Further, with respect to the luminance signal of a home VTR, image improvement such as dropout compensation and line correlation noise reduction using the correlation for each horizontal period has been performed. The dropout compensating circuit is a circuit that substitutes the line correlation of an image with a signal before 1H when a dropout occurs in a reproduced signal. As a signal,
Although it is easy to perform in the reproduction FM signal system, it has a drawback of generating switching noise. Therefore, at present, it is mainly used to use the luminance signal after demodulation. FIG. 4B shows an example of the dropout compensation circuit. FIG.
In (b), reference numeral 7 denotes an input terminal to which a reproduction luminance signal is input. The reproduced luminance signal normally passes through the switch circuit 8 and is output from the output terminal 10. The reproduced luminance signal passed through the switch circuit 8 is also input to the 1H delay element 9, and a 1H delayed reproduced luminance signal is obtained. This 1H delay reproduction luminance signal is input to the other input terminal of the switch circuit 8. When the presence of a dropout is detected by the dropout detector 12 in the FM signal input from the input terminal 11, the switch circuit 8 switches to 1
An H-delay reproduction luminance signal is selected and output. This output compensates for dropout. Since this dropout compensating circuit is a closed circuit, continuous dropouts of 1H or more are compensated by the signal of 1H before.

The line correlation noise reduction circuit has a strong line correlation between the reproduced luminance signal and the 1H-delayed reproduced luminance signal, and utilizes the fact that a noise component having no line correlation is obtained in the differential outputs of the two. I have. FIG. 4C shows an example of the line correlation noise reduction circuit. In FIG. 4C, reference numeral 13 denotes an input terminal to which a reproduced luminance signal is input. This reproduced luminance signal is input to the differential amplifier 15 and also to the 1H delay element 14,
Here, a 1H delay reproduction luminance signal is obtained. The 1H delayed reproduction luminance signal is input to the differential amplifier 15 as described above, and a differential output between 1H is obtained. This difference output is a noise component, and this noise component is input to the limiter 16 to extract only a minute high-frequency noise.
7, the signal is mixed with the reproduced luminance signal, and a luminance signal with reduced noise is obtained at the output terminal 18.

[0006] Luminance image quality improvement circuits, both using the 1H delay element, such as the above-mentioned dropout compensation circuit and line correlation noise reduction circuit, are usually constructed of the same circuit system, and one 1H delay element is used for each. It is common to share the circuit. For this reason, most PAL VTRs at present have at least one 2H delay element for color signals and one 1H delay element for luminance signals. Incidentally, the 2H delay element is relatively large, and VT
Not only one of the hindrance factors when miniaturizing R,
The costs are relatively high. Conventionally, such 2H
2H using a single 1H delay element without using a delay element
One that obtains a delayed signal is also known (Japanese Unexamined Patent Publication No.
No. 284). This is a comb filter which converts a signal once delayed by the 1H delay element and delays it again through the 1H delay element.

FIG. 4D mainly shows a portion related to the delay device of the comb filter. The output of the high-pass filter 20 and the 1H frequency-converted to a low frequency by the frequency converter 21 are shown in FIG. High-pass filters 24 and 1H for extracting the signal delayed by 1H from the output of the 1H delay line 22;
A frequency converter 25 is provided which converts the output of the delay line 22 into a high-frequency band and sends it to a low-pass filter 26. The video signal input from the input terminal 19 passes through the 1H delay line 22 at the original frequency, is converted to a lower frequency in frequency, passes through the 1H delay line 22 again, and is converted to the original frequency. Accordingly, the video signal that has passed through the 1H delay line 22 twice is output from the low-pass filter 26, and the 1H
A signal that has passed through the delay line 22 once and a signal that has not passed through the delay line 22 are also obtained.

[0008]

In the apparatus for removing crosstalk of a reproduced carrier color signal in the PAL system VTR or the like, the carrier color signal is delayed by 2H by using a technique known in the above publication. Even if the 1H delay element is used, a VTR or the like requires a 1H delay element for the luminance signal in addition to the 1H delay element.
Requires an H delay element. The present invention is based on the carrier color signal 2.
An object of the present invention is to provide an apparatus for removing crosstalk of a reproduced carrier chrominance signal such as a VTR in which an H delay and a 1H delay of a luminance signal can be performed by a single 1H delay element, and a delay apparatus used therefor.

[0009]

According to the present invention, there is provided a crosstalk canceling apparatus for a reproduced carrier color signal, such as a VTR, for solving the above-mentioned problems. An adder for adding the added signal, and a signal added by the adder to a television signal 1
A 1H delay element for delaying a horizontal period, a frequency converter for converting the output signal of the 1H delay element into a signal in a frequency band not overlapping with the input signal to obtain the frequency-converted signal, and the 1H delay element And a low-pass filter for extracting a signal in a frequency band corresponding to the frequency band of the luminance signal from the output signal of the 1H delay element, and a frequency band corresponding to the frequency band of the frequency-converted signal obtained from the output signal of the 1H delay element. A subtractor for subtracting the input signal from a signal obtained by converting the signal to return to the frequency band of the original signal before the frequency conversion; and a frequency band of the signal obtained from the subtractor is a frequency band of the carrier color signal. And a band-pass filter for limiting the pass band so that

According to another aspect of the present invention, there is provided a delay device for adding an input signal including a luminance signal and a carrier chrominance signal to a frequency-converted signal described later, and the adder. Is added to the signal of TV signal 1
A 1H delay element for delaying a horizontal period, a frequency converter for converting the output signal of the 1H delay element into a signal in a frequency band not overlapping with the input signal to obtain the frequency-converted signal, and the 1H delay element And a low-pass filter for extracting a signal in a frequency band corresponding to the frequency band of the luminance signal from the output signal of the above-mentioned 1H delay element. It is characterized in that a signal delayed by one horizontal period and, for convenience, delayed by two horizontal periods is obtained.

[0011]

In the apparatus for removing crosstalk of a reproduced carrier chrominance signal such as a VTR constructed as described above, a luminance signal included in an input signal is extracted by a low-pass filter after being delayed by 1H by the 1H delay element. Thus, a 1H delayed luminance signal is obtained. The 1H delayed luminance signal can be used for the well-known dropout compensation, line correlation noise reduction, and the like. On the other hand, the carrier chrominance signal included in the input signal is delayed by 1H by the 1H delay element, and then converted by the frequency converter into a signal in a frequency band that does not overlap with the frequency band of the input signal. The signal is again input to the 1H delay element and delayed by 1H. Thus, the signal delayed by 2H is frequency-converted so as to return to the frequency band of the original signal before being converted by the frequency converter, and is subtracted from the input signal by a subtractor. The frequency band of the signal obtained from the subtractor is band-limited by a band filter so as to be the frequency band of the carrier chrominance signal. Then, the crosstalk of the carrier color signal is removed by the above subtraction.

In the delay device configured as described above, the luminance signal included in the input signal is delayed by 1H by the 1H delay element and then extracted by the low-pass filter to obtain a 1H delayed luminance signal. Can be The 1H delayed luminance signal can be used for the well-known dropout compensation, line correlation noise reduction, and the like.
On the other hand, the carrier chrominance signal included in the input signal is
After being delayed by 1H by the H delay element, the signal is converted into a signal of a frequency band not overlapping with the frequency band of the input signal by the frequency converter, input again to the 1H delay element via the adder, and delayed by 1H. . In this way, a signal delayed by 2H is obtained. The signal delayed by 2H is frequency-converted so as to return to the frequency band of the original signal before being converted by the frequency converter, and is subtracted from the input signal by a subtractor. The crosstalk of the reproduced carrier chrominance signal is removed by band-limiting the band by using a band filter so that the frequency band of the carrier chrominance signal becomes the frequency band of the carrier chrominance signal.

[0013]

1 and 2 show an embodiment of the present invention.
Will be described. FIG. 1 is a block diagram of a chrominance signal crosstalk removing device, and the same reference numerals as those in FIG. 4A denote the same components, and a detailed description thereof will be omitted. FIG. 2 shows an output signal spectrum waveform of each block in FIG. In FIG. 1, reference numeral 50 denotes an input terminal to which a reproduced carrier chrominance signal is input, and reference numeral 51 denotes an input terminal to which a reproduced luminance signal is input. Reference numeral 52 denotes an adder, which is a reproduction carrier chrominance signal input from the input terminal 50, a reproduction luminance signal input from the input terminal 51, and a double balance modulator 53 described later.
Is added to the signal output from. Reference numeral 54 denotes a 1H delay element, which delays the signal output from the adder 52 by 1H. 55 is a band-pass filter, and a 1H delay element 5
Only signals in the frequency band corresponding to the frequency band of the carrier chrominance signal are passed from the signal output from 4. Reference numeral 56 denotes a frequency converter, which comprises the double balanced modulator 53 and a band-pass filter 55, and converts the frequency of the signal output from the 1H delay element 54. The double balanced modulator 5
The reference numeral 3 double-balance modulates the carrier from the carrier oscillator 57 by the signal output from the band-pass filter 55.

Reference numeral 58 denotes a band-pass filter.
From the signal output from the H delay element 54, only the signal in the frequency band corresponding to the lower band frequency band of the double balanced modulation output of the double balanced modulator 53 is passed. Numeral 59 denotes a double balance modulator, which double-balances the carrier from the carrier oscillator 57 with a signal output from the band-pass filter 58. 60 is a frequency converter,
The bandpass filter 58 and the double balanced modulator 59 convert the frequency of the signal output from the 1H delay element 54. Reference numeral 5 denotes the aforementioned subtractor, which subtracts the reproduced carrier color signal input from the input terminal 50 and the signal output from the double balanced modulator 59. Reference numeral 61 denotes a band pass filter, which passes only a signal in a frequency band corresponding to the frequency band of the carrier chrominance signal from the signal output from the subtractor 5.

Reference numeral 6 denotes the above-mentioned output terminal, which outputs a carrier chrominance signal from the band-pass filter 61 from which crosstalk has been removed. Reference numeral 62 denotes a low-pass filter, which passes only signals in a frequency band corresponding to the frequency band of the reproduced luminance signal among the signals output from the 1H delay element 54. An output terminal 63 outputs a 1H-delayed reproduction luminance signal output from the low-pass filter 62.

Next, the operation of FIG. 1 will be described with reference to FIG. In FIG. 2, the head of the spectrum waveform is drawn in an arc shape, the current signal is, the head is sharpened in a square, the signal is 1H past, and the head is horizontal. Indicates that the signal is 2H past, and black circles indicate the direction of the signal waveform. A reproduction carrier color signal is input from the input terminal 50. The spectral waveform of this input signal is as shown in FIG. 2A, and the center frequency of the reproduced carrier chrominance signal is 4.43 MHz. This reproduced carrier color signal is referred to as a non-delayed carrier color signal. At the same time when the non-delayed carrier color signal is input to the input terminal 50, the input terminal 5
1 receives a reproduced luminance signal. This reproduced luminance signal has a frequency band of about 0 to 3 MHz, similarly to the frequency band of the reproduced luminance signal in a normal VTR, and its spectrum waveform is as shown in FIG. This reproduced luminance signal is called a non-delayed luminance signal.

The non-delayed carrier chrominance signal, the non-delayed luminance signal, and an output signal described later from the double balanced modulator 53 are input to an adder 52 and added. The spectrum waveform of the added signal is as shown in FIG.
The signal around 0 to 3 MHz is the non-delayed luminance signal, 4.4
The signal around 3 MHz is the non-carrier color signal, and (n-4.43) MHz
Signals near (n + 4.43) MHz and near double balanced modulation 5
3, which will be described later. The non-delayed carrier chrominance signal, the non-delayed luminance signal, and the vicinity of (n-4.43) MHz and (n + 4.
43) The signal around MHz is input to the 1H delay element 54,
The output is delayed. The spectrum waveform of this output signal is as shown in FIG. 0-3MH in FIG. 2 (d)
The signal near z is a signal that is 1H past at the same time as the non-delayed luminance signal is input to the 1H delay element 54,
This is called a 1H delayed luminance signal. The signal near 4.43 MHz is a signal that is 1H past at the same time as the non-delayed carrier chrominance signal is input to the 1H delay element 54, and is referred to as a 1H delayed carrier chrominance signal. In addition, around (n-4.43) MHz and (n + 4.43)
The signal near 43) MHz is also a 1H delay signal of the signal near (n-4.43) MHz and near (n + 4.43) MHz in FIG.

The signal output from the 1H delay element 54 is band-limited by a band-pass filter 55, and is 4.43 MHz.
Only the signal near z, that is, the 1H carrier color signal is extracted. FIG. 2E shows the spectrum waveform of the 1H carrier color signal.
Shown in The 1H delayed carrier chrominance signal output from the band-pass filter 55 is input to the double balanced modulator 53, and double-balanced modulates the n MHz carrier output from the carrier oscillator 57. The output spectrum waveform of the double balanced modulator 53 is as shown in FIG. 2 (f), and the 1H delayed carrier chrominance signal near 4.43 MHz obtained by double balanced modulation of the carrier of frequency nMHz is a difference (n-4.43). ) MHz and the sum (n +
4.43) Appears as double balanced modulation output around MHz. This double balanced modulation output is referred to as a 1H delayed double balanced modulation signal. The frequency nMHz of the carrier output from the carrier oscillator 57 is output from the frequency converter 56 and
2 is set so as to be a signal in a frequency band that does not overlap with the non-delayed carrier chrominance signal and the non-delayed luminance signal.

Now, the 1H delayed double balanced modulation signal is
The non-delayed carrier chrominance signal and the non-delayed luminance signal are input to the adder 52 at the same time as the input. Therefore, the output spectrum of the adder 52 shown in FIG.
3) A signal near MHz and a signal near (n + 4.43) MHz are the 1H delay double balanced modulation signal, and the output spectrum of the 1H delay element 54, (n-4.43) in FIG. MH
The signals in the vicinity of z and in the vicinity of (n + 4.43) MHz are signals obtained by delaying the 1H delay double balanced modulation signal by 1H, that is, the same time as the 1H delay double balanced modulation signal is input to the 1H delay element 54. At the same time when the non-delayed carrier chrominance signal is input to the adder 52 and the subtractor 5 at the same time. This 2H past signal is referred to as a 2H delayed double balanced modulation signal.

The signals output from the 1H delay element 54, ie, a 1H delayed luminance signal, a 1H delayed carrier color signal, and 2
The H-delay doubly balanced modulation signal is input to the band-pass filter 58, and only a signal in a frequency band corresponding to the lower-band frequency band of the 2H-delay doubly balanced modulation signal is extracted.
The spectrum waveform of the output signal of the band-pass filter 58 is as shown in FIG. 2 (g), and this output signal is referred to as a 2H delay double balanced modulation signal lower sideband. The lower band of the 2H-delayed double-balanced modulated signal output from the band-pass filter 58 is input to a double-balanced modulator 59, and the same carrier oscillator 57 used for the double-balanced modulator 53 is used.
Is again double-balanced modulated with the carrier of frequency nMHz. The spectrum waveform of the output signal of the double balanced modulator 59 is as shown in FIG. The lower sideband of the 2H-delayed double-balanced modulated signal near (n-4.43) MHz obtained by doubly balanced modulating the carrier having the frequency of nMHz is {n- (n-4.43)} MHz = 4.43.
MHz and its sum {n + (n-4.43)} MHz = 2n-4.43MHz
Appears nearby. The output signal of the double balanced modulator 59 is referred to as a secondary double balanced modulated signal, and a signal in the vicinity of 4.43 MHz, which is the lower band of the secondary double balanced modulated signal, corresponds to the frequency band of the carrier chrominance signal. Since it has returned to the frequency band, it is called a 2H delayed carrier chrominance signal.

The 2 output from the double balanced modulator 59
The next double balanced modulation signal and the non-delayed carrier chrominance signal are input to a subtractor 5 and subtracted. The spectral waveform of the output signal of the subtractor 5 is as shown in FIG. 2 (i). The signal around 4.43 MHz is the lower band of the non-delayed carrier chrominance signal and the secondary double balanced modulation signal, that is, the 2H delayed carrier chrominance. The signal is a signal obtained by subtracting the signal. The signal output from the subtracter 5 is input to a band-pass filter 61, and a signal in a frequency band corresponding to the frequency band of the carrier chrominance signal, that is, a color signal from which crosstalk has been removed is obtained. This color signal is output from the output terminal 6. Further, the signal output from the 1H delay element 54 is also input to a low-pass filter 62, and only a signal in a frequency band corresponding to the frequency band of the luminance signal, that is, a 1H delayed luminance signal, is taken out. Is output.

In the above description, the reproduced carrier color signal is input to the input terminal 50. Instead of the reproduced carrier color signal, the reproduced carrier color signal obtained by performing balanced modulation of the reproduced low-frequency conversion color signal to the high frequency band is obtained. When a reproduction balanced modulation signal including a chrominance signal is input, the frequency nMHz of the carrier output from the carrier oscillator 57 is set to the double balanced modulator 5.
If the output signal subjected to the double balanced modulation in 3 is set to a frequency that does not overlap with the frequency band corresponding to each frequency band of the reproduction balanced modulation signal and the reproduction luminance signal, the same as the case of inputting the reproduction carrier chrominance signal is performed. The effect is obtained.

In FIG. 1, as means for obtaining only the carrier chrominance signal from which crosstalk has been removed at the output terminal 6,
Although the band-pass filter 61 is provided after the subtractor 5,
It is not always necessary to provide it at the subsequent stage. For example, if a reproduced carrier color signal is input to the input terminal 50, FIG.
The same effect can be obtained by providing a band-pass filter 63 similar to the band-pass filter 61 between the double balanced modulator 59 and the subtractor 5 as shown in FIG. Also,
When the reproduction balanced modulation signal is input to the input terminal 1, a band-pass filter 64 similar to the band-pass filter 63 is connected to the input terminal 50 in addition to the band-pass filter 63 as shown in FIG. The band-pass filter 64 may be provided between the band-pass filter 64 and the subtractor 5 as shown in FIG.
Is provided between the input terminal 50 and the subtractor 5 and the band-pass filter 61 is provided between the subtractor 5 and the output terminal 6.

When a reproduction balanced modulation signal is input to the input terminal 50 with the configuration as shown in FIG. 3B or 3C, the voltage between the band-pass filter 64 and the subtractor 5 is reduced. A reproduced carrier chrominance signal that has not been subjected to crosstalk removal processing can be extracted, and this signal can be used as an APC circuit signal of a color signal used in a VTR or the like, as is well known. In FIG. 1, if a signal is extracted from between the band-pass filter 55 and the double balanced modulator 53, a 1H delayed carrier color signal can be obtained. FIG.
In the above, the frequency converters 56 and 60 may have other configurations, and may not use balanced modulation unless a carrier wave is a problem. Further, in FIG. 1, when there is an influence of the delay and the amplitude change by each band limiting means and the modulator, the amplitude and the phase of the non-delayed carrier color signal and the 2H delayed carrier color signal are matched in the subtraction by the subtracter 5. It is desirable to provide such adjustment means.

[0025]

As described above, according to the present invention, the 2H delay of the carrier chrominance signal and the 1H delay of the luminance signal are equal to each other.
A crosstalk removing device for a reproduced carrier chrominance signal such as a VTR, which can be achieved by using a single 1H delay element, and a delay device used therefor are obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a spectrum waveform diagram of an output signal of each block in FIG. 1;

FIG. 3 is a block diagram of a main part showing another embodiment of the present invention.

FIG. 4 is a block diagram showing a conventional example.

[Explanation of symbols]

 Reference Signs List 5 subtractor 6 output terminal 50, 51 input terminal 52 adder 53 double balanced modulator 54 1H delay element 55 band pass filter 56 frequency converter 57 carrier oscillator 58 band pass filter 59 double balanced modulator 60 frequency converter 61 Band pass filter 62 Low pass filter 63 Band pass filter 64 Band pass filter

Claims (2)

(57) [Claims] An adder for adding an input signal including a luminance signal and a carrier chrominance signal to a frequency-converted signal described later;
A 1H delay element for delaying the signal added by the adder by one horizontal period of the television signal, and an output signal of the 1H delay element is frequency-converted into a signal in a frequency band that does not overlap with the input signal. Frequency converter for obtaining a signal obtained from the 1H delay element, a low-pass filter for extracting a signal in a frequency band corresponding to the frequency band of the luminance signal from the output signal of the 1H delay element, and the frequency obtained from the output signal of the 1H delay element A subtractor for subtracting the input signal from a signal obtained by converting a signal in a frequency band corresponding to the frequency band of the converted signal back to the frequency band of the original signal before the frequency conversion, and a signal obtained from the subtractor. And a band-pass filter for limiting a pass band so that the frequency band of the signal to be obtained is the frequency band of the carrier chrominance signal. Crosstalk removing device of the reproduced carrier chrominance signal. 2. An adder for adding an input signal including a luminance signal and a carrier chrominance signal to a frequency-converted signal described later;
A 1H delay element for delaying the signal added by the adder by one horizontal period of the television signal, and an output signal of the 1H delay element is frequency-converted into a signal in a frequency band that does not overlap with the input signal. And a low-pass filter for extracting a signal in a frequency band corresponding to a frequency band of a luminance signal from an output signal of the 1H delay element. And a signal which is further delayed by one horizontal period by the 1H delay element to obtain a signal delayed by two horizontal periods.