JP2715542B2 - Color signal processing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording apparatus having a color video signal format conversion circuit.

2. Description of the Related Art In recent years, with the worldwide spread of video tape recorders (hereinafter referred to as VTRs), a large amount of video soft tapes has been on the market. Against this background, video format conversion technology,
That is, a technique of extracting a PAL video signal from an NTSC tape or extracting an NTSC video signal from a PAL tape is receiving attention.

Hereinafter, an example of a conventional color signal processing apparatus of a VTR that records and reproduces a PAL color video signal will be described with reference to the drawings.

FIG. 5 is a block diagram of a reproduction system of a conventional PAL VTR color signal processing device. In FIG. 1, a reproduced color signal input from an input terminal 1 is amplified by an amplifier 2, and a low-pass filter (hereinafter referred to as LPF) 3 extracts a low-frequency conversion color signal. The amplitude of the low-frequency converted chrominance signal is controlled by an automatic gain control circuit (hereinafter referred to as ACC) 4 so that the color burst signal becomes a constant level.
Supplied to The balanced modulator 5 converts the frequency, and further removes unnecessary components generated at the time of balanced modulation in a band-pass filter (hereinafter referred to as BPF) 6 to extract a reproduced carrier chrominance signal. Next, the crosstalk component of the adjacent video track is removed by the comb filter 22, and the signal is output from the output terminal 8. The phase comparator 9 compares the phase of the color burst signal of the carrier color signal output from the comb filter 22 with the reference signal (hereinafter referred to as SC) from the reference oscillator 23. By the way, the frequency of _SC will be referred to as _SC hereinafter. The error signal passes through the LPF 11 and has a 321 times horizontal scanning frequency (hereinafter, referred to as _H ) voltage-controlled oscillator (hereinafter, referred to as VCO) 12.
Control. VCO12 oscillation frequency in 1/8 frequency divider
Four output signals that are 1/8 frequency-divided and have phases different by 90 degrees are supplied to the selection circuit 14. In the balanced modulator 15, the reference oscillator 23 is used.
The balance modulation is carried out with the SC from the, and unnecessary components are removed by the BPF 16 to make the carrier of the balance modulator 5. As described above, the phase fluctuation generated at the time of reproduction is corrected, and the color signal from which the crosstalk from the adjacent video track has been removed is output.

Here, the operation of the comb filter during reproduction will be described. FIG. 6 is a block diagram of the configuration of the comb filter 22 used in the PAL system VTR. The input terminal 17 for inputting a signal and 2H capable of delaying the signal by two horizontal scanning periods (2H) are shown. A delay line 18, a level adjuster 19 for adjusting the level of a signal not delayed, an adder 20 for adding a signal delayed by 2H and a signal not delayed, and an output terminal 21 for outputting a signal from the adder 20 Having.
One of the color signals input from the input terminal 17 is a 2H delay line 24.
In the PAL system _SC , the signal is delayed by 2H as the PAL system _H , and the signal passed through the level adjuster 19 is added to the adder 20. Of these two signals, a crosstalk component from an adjacent video track is used. Certain antiphase components cancel each other out, and the color signal output from the output terminal 21 is output as only the original signal.

FIG. 3 shows a color signal phase pattern on a PAL video tape, and FIG. 7 shows a process of removing crosstalk components of a color signal from an adjacent video track by the comb filter of FIG.

In FIG. 3, among two heads having different azimuth angles, the color signal phase on the video track by the first head is 0 °, and the color signal phase on the video track by the second head is 90 ° every 1H. Since the recording is performed with the phase rotated, for example, when the color signal is reproduced by the first head, the phase of the color signal is as shown in FIG. 7A. In FIG. 7, the solid line shows the phase and amplitude of the original signal, and the broken line shows the phase and amplitude of the crosstalk component from the adjacent video track. One of the color signals D reproduced by the first head is input to the 2H delay line 24, and the PAL system _H = 15625
Delayed by 2H in Hz to become the signal of FIG.
The signal is input to the adder 20. On the other hand, the color signal D reproduced by the first head is input to the adder 20 through the level adjuster 19. In the adder 20, the signal shown in FIG. 7E and the crosstalk component from the adjacent video track included in the output signal D 'from the level adjuster 19 are canceled out due to the opposite phase components, while the original signal is added. As a result, the signal output from the comb filter 22 becomes only the original signal as shown in FIG. 7F, and the crosstalk component from the adjacent video track is removed.

Here, a case where a PAL color signal is reproduced by an NTSC TV set will be described.

The relationship between the color signal and the luminance signal in the PAL system is different from the relationship between the color signal and the luminance signal in the NTSC system. That is, _SC and _H are different between the NTSC system and the PAL system. Therefore, when reproducing a PAL color signal on an NTSC TV set, the _SC needs to be the same as the NTSC _SC = 3579545 Hz. Further, as for the comb filter 22 for removing the crosstalk component from the adjacent video track, since the recorded signal is of the PAL system, the comb filter for removing the crosstalk component from the adjacent video track includes: A 2H delay line with PAL system _H = 15625 Hz is required.

However, in the configuration described above, the 2H delay line 24 used in the comb filter 22 has a PAL system _SC = 44333619 Hz.
In this example, a 2H delay line of PAL system _H = 15625 Hz is used. FIG. 8 shows a process of removing crosstalk between adjacent video tracks when the PAL color signal reproduced using the NTSC _SC is input to the comb filter of FIG.

When the PAL color signal A reproduced using the NTSC _SC = 3579545 Hz shown in FIG. 8 is input to the input terminal 17, 2H
The output signal from the delay line 18 becomes, for example, G, and the signal obtained by adding G and A 'by the adder 20 becomes H. Therefore, not only the crosstalk component cannot be removed from the adjacent video track, but also the phase of the original signal changes.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a comb-type that can remove crosstalk components from adjacent video tracks without changing the phase of an original signal when converting a PAL color video signal to an NTSC color video signal. An object of the present invention is to provide a color signal processing device having a filter.

Means for Solving the Problems In order to solve the above problems, the chrominance signal processing apparatus of the present invention comprises a cross section of a reproduced PAL chroma signal having a horizontal synchronization frequency _H = 15625 Hz and a color subcarrier _SC = 3579545 Hz from an adjacent video track. It has a comb filter capable of removing a talk component.

Action The present invention has the above-described configuration, and the NTSC system _SC = 3579
In the PAL color signal reproduced using 545 Hz, the crosstalk component from the adjacent video track can be removed, and PA
When the L tape is reproduced as an NTSC video signal, the image quality can be improved.

Embodiment Hereinafter, a color signal processing apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a reproduction system of a VTR color signal processing device according to an embodiment of the present invention. In the figure, a reproduced color signal input from an input terminal 1 is amplified by an amplifier 2, and a low-frequency conversion color signal is extracted by an LPF 3. The amplitude of the low-frequency converted color signal is controlled by the ACC 4 so that the color burst signal becomes a constant level, and is supplied to the balanced converter 5. The balanced modulator 5 performs frequency conversion, and further removes unnecessary components generated at the time of balanced modulation in the BPF 6, and extracts a reproduced carrier chrominance signal. Next, the crosstalk component from the adjacent video track is removed by the comb filter 7 and output from the output terminal 8. The phase comparator 9 compares the phase of the color burst signal of the carrier color signal output from the comb filter 7 with the SC from the reference oscillator 10. The error signal passes through the LPF 11 and controls the VCO 12. The oscillation frequency of the VCO 12 is divided by 1/8 in the 1/8 frequency dividing circuit, and four output signals having phases different by 90 degrees are supplied to the selecting circuit 14. The balanced modulator 15 performs balanced modulation with the SC from the reference oscillator 10, removes unnecessary components with the BPF 16, and uses it as a carrier of the balanced modulator 5. As described above, the phase fluctuation generated at the time of reproduction is corrected, and the color signal from which the crosstalk from the adjacent video track has been removed is output.

Here, consider a case in which a PAL tape is reproduced and converted to an NTSC video signal. FIG. 2 is a block diagram of the configuration of the comb filter 7 used in the above case. One of the color signals input from the input terminal 17 is a 2H delay line 18 and the PAL system _H = 3579545 Hz in the NTSC system _SC = 3579545 Hz.
Delayed by 2H at 15625Hz, while level adjuster 1
The signal having passed through 9 is added to an adder 20 and output from an output terminal 21.

FIG. 3 shows a color signal phase pattern on a PAL video tape, and FIG. 4 shows a process of removing a crosstalk component of a color signal from an adjacent video track by the comb filter of FIG.

In FIG. 3, of the two heads having different azimuth angles, the color signal phase on the video track by the first head is 0 °, and the color signal phase on the video track by the second head is 90 ° every 1H. Since the recording is performed with the phase delayed, for example, when the color signal is reproduced by the first head, the phase of the color signal is as shown in FIG. 4A. In FIG. 4, the solid line shows the phase and amplitude of the original signal, and the broken line shows the phase and amplitude of the crosstalk component from the adjacent video track. One of the color signals A reproduced by the first head is input to the 2H delay line 18, and the PAL system
The signal of FIG. 4B is delayed by 2H at _H = 15625 Hz, and is input to the adder 20. On the other hand, the color signal A reproduced by the first head is input to the adder 20 through the level adjuster 19. In the adder 20, the signal shown in FIG. 4B and the crosstalk component from the adjacent video track included in the output signal A 'from the level adjuster 19 are canceled out due to the components having opposite phases, while the original signal is added. As a result, the output signal from the comb filter 7 becomes only the original signal as shown in FIG. 4C, the crosstalk component from the adjacent video track is removed, and the phase of the original signal does not change.

In FIG. 1, while the signal from which the crosstalk component has been removed from the adjacent video track is output from the output terminal 8, the signal is also input to the phase comparator 9. The error signal output from the phase comparator 9 as compared with the case where the crosstalk component exists is an error signal more faithful to the original signal.
A color signal with little phase fluctuation generated during reproduction is reproduced.

As described above, according to the present invention, the crosstalk component from the adjacent video track is changed without changing the phase of the PAL chroma signal having the horizontal synchronization frequency _H = 15625 Hz and the color subcarrier _SC = 3579545 Hz reproduced from the VTR. Can be removed,
Image quality can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a color signal processing device according to the present invention, FIG. 2 is a block diagram of a comb filter used in the device, and FIG. 3 is a color signal phase on a video tape in the PAL system. FIG. 4 is an explanatory view showing a process of removing a crosstalk component of a color signal from an adjacent video track in FIG. 2, FIG. 5 is a block diagram showing a conventional color signal processing device, and FIG. FIG. 7 is a block diagram of a comb filter used in the apparatus, FIG. 7 is an explanatory diagram showing a process of removing a crosstalk component of a color signal from an adjacent video track in FIG. 6, and FIG. 8 is an NTSC system _SC in FIG. FIG. 7 is an explanatory diagram showing a process of removing a crosstalk component from an adjacent video track of a color signal when a converted PAL color signal is input. 1 input terminal, 2 amplifier, 3 LPF, 4 AC
C, 5: Balanced modulator, 6: BPF, 7: comb filter, 8: Output terminal, 9: Phase comparator, 10: Reference oscillator (NTSC _SC = 3579545Hz), 11 ... LPF, 12 ……
VCO, 13: 1/8 frequency divider, 14: Selector, 15: Balanced modulator, 16: BPF, 17: Input terminal, 18: 2H delay line, 19: Level adjuster, 20 adder, 21 output terminal, 22 comb filter, 23 reference oscillator (PAL system _SC = 44333619Hz), 24 2H delay line.

Claims (1)

(57) [Claims] A servo system capable of recording / reproducing image signals of several kinds of field frequencies is provided, and a tape recorded by a video tape recorder of a PAL system while employing an NTSC system as a color signal processing circuit. At the time of reproduction, the two heads having different azimuth angles have a function of making the phase of the color signal constant and invariable during one horizontal scanning period in the first head, and delaying the phase of the color signal by 90 ° in each horizontal scanning period in the second head. In a magnetic recording / reproducing apparatus having a color signal processing circuit capable of reproducing a signal recorded in the PAL system and reproducing on a TV screen of the NTSC system, a 2H delay line and an input / output signal of the 2H delay line are used. A comb filter for level adjustment and addition is provided, and by adjusting the reference transmission frequency of the 2H delay line to the NTSC system, adjacent video traffic included in the signal when converting from the PAL system to the NTSC system. Color signal processing apparatus, characterized in that for removing crosstalk components from click.