JPH05207509A - Chrominance signal processing circuit - Google Patents

Abstract

PURPOSE:To simplify the circuit by providing a means outputting a signal demodulating a color difference signal, a low frequency conversion chrominance subcarrier generating means and a means modulating a demodulation signal with a low frequency conversion chrominance subcarrier and outputting a low frequency conversion chroma signal to the processing circuit. CONSTITUTION:A band-limited chrominance difference signal fed to a modulator 17 is modulated by a frequency signal fed from a ROM 24 when the circuit receives an NTSC composite signal and the result is fed to an LPF 18. The signal fed to the LPF 18 is band-limited so as to prevent interference with a frequency-modulated luminance signal and a low frequency conversion chroma signal subjected to color processing at recording is fed to an output terminal 19. Upon the receipt of a Y/C separate signal by the processing circuit, a separate S-Y signal is fed to a delay device 11 via a 1H delay device 2 and the result is fed to an output terminal 13 as a luminance signal. A separate S-C signal is fed through an input terminal 9 and fed to a switch 8 via a 1H delay device 3 and the result is outputted to a modulator 14 and processed similarly in the case of the input of the NTSC composite video signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color signal processing circuit in a device for processing a video signal of a video tape recorder.

[0002]

2. Description of the Related Art An example of a conventional video signal processing device will be described below.
A description will be given with reference to FIG. 2, which is a block diagram of chroma signal processing at the time of recording a video signal used in the VHS system, which is cited from “Introduction to Home VTR” (Corona Corporation, Yokoyama, Hirota et al .; P171). In the chroma signal processing at the time of recording the VHS system video signal, Y / C separation is performed to extract a color signal, and the color signal is subjected to low frequency conversion.

In FIG. 2, the NTSC composite video signal is supplied to the Y / C separator 28 and the f _H separator 20 via the input terminal 27. A color signal is extracted from the composite video signal supplied to the Y / C separation device 28, the amplitude of the burst signal is made constant by the ACC 15, and then supplied to the frequency converter 31. f _H separation device 2
The horizontal synchronizing frequency (hereinafter referred to as f _H ) is extracted from the composite video signal supplied to 0, and the frequency multiplier 21
And counter 2 are supplied. F _H supplied to the frequency multiplier 21 is 160 multiplied, 160f _H is supplied to the counter 23. The counters 22 and 23 are supplied with f
Each of _H and 160f _H is counted and supplied to the ROM 24. The drum rotation pulse is stored in the ROM via the input terminal 26.
24. The ROM 24 is called up by the outputs of the counters 22 and 23 and the drum rotation pulse, and a 40 f _H square wave processed for recording color process processing is obtained and supplied to the frequency converter 29.

The frequency converter 29 is supplied with a frequency of 3.58 MHz from the crystal oscillator 30 and a square wave of 40 f _H processed from the ROM 24 for the color process processing at the time of recording, and for the color process processing at the time of recording. The processed signal of the frequency of 3.58 MHz + 40 f _H is supplied to the frequency converter 31. In the frequency converter 31, the ACC
The chroma signal from 15 is low-pass converted to a frequency of 40 f _H which has been color-processed during recording, and this low-pass converted chroma signal is supplied to a low-pass filter (hereinafter referred to as LPF) 18. The low-frequency conversion chroma signal output from the LPF 18 is supplied to the output end 19, amplified by a recording amplifier (not shown), and then combined with the FM-modulated luminance signal.

However, this method has a problem that the circuit scale becomes large because two frequency converters are used and a crystal oscillator is also required. Further, since the Y / C separation unit and the color signal processing unit are considered separately, and the processing is complicated, there is a limit in improving the performance.

[0006]

As described above, in the conventional apparatus, the color signal is processed for Y / C separation and processing for producing the low-frequency conversion chroma signal, but this processing is complicated. Therefore, there is a problem that there is a limit to the improvement of performance. It is an object of the present invention to eliminate the drawbacks of the prior art as described above, improve the performance by simplifying the signal processing system, and reduce the cost and the mounting area by reducing the hardware.

[0007]

In order to achieve the above object, in the present invention, a composite video signal is supplied, a means for outputting a demodulated signal obtained by demodulating a color difference signal, and a low frequency conversion color subcarrier are provided. A color signal processing circuit comprising: a low-frequency conversion color subcarrier generating means for outputting; and a demodulation means for modulating the demodulated signal with the low-frequency conversion color subcarrier and outputting a low-frequency conversion chroma signal. I will provide a.

[0008]

In the structure thus constructed, the NTS
In order to record the C signal on the VTR, first, Y / C separation is performed. However, in the signal processing of the home VTR, the chroma signal to be finally obtained is the chroma signal converted to the low frequency range, so that it is not necessarily about 3.58 MHz. It is not necessary to output the color signal of. For this reason, the circuit configuration is divided into a color signal extraction circuit for luminance signal separation and a color signal extraction circuit for low-frequency conversion chroma, and in the color signal extraction circuit for low-frequency conversion chroma signal,
If the color difference signal is extracted at the time of color signal separation and then modulated to the frequency of the low-frequency conversion chroma, the low-frequency conversion color signal subjected to the color process during recording can be obtained by changing the modulation phase. .. The luminance signal can be obtained by outputting a color signal extraction circuit for luminance signal separation or by generating a color signal from the color difference signal and then subtracting the color signal from the composite signal.

[0009]

EXAMPLES Examples of the present invention will now be described with reference to NTSC.
The VHS format video of the format will be described in detail with reference to FIG. In FIG. 1, switches 8, 10, and 25 are NTS.
When inputting C composite video signal, select A side, Y
When the / C separate signal is input, the B side is selected.

First, an NTSC composite video signal will be described. The NTSC composite video signal is supplied via an input terminal 1 to a 1H delay device 2, a bandpass filter (hereinafter referred to as BPF) 4, and an f _H separation device 20. The NTSC composite video signal supplied to the 1H delay device 2 is delayed by one horizontal scanning period and supplied to the 1H delay device 3 via the BPF 5, the delay device 11 and the switch 10. The signal supplied to the 1H delay device 3 is further delayed by one horizontal scanning period and supplied to the BPF 6. BPF
The band limits of the composite video signals supplied to 4, 5 and 6 are supplied to the 3-line dynamic comb filter 7, respectively. 3-line dynamic comb filter 7
Color signals are separated from the three composite video signals supplied to the demodulator 14 and are supplied to one input terminal of the demodulator 14 and the switch 25.

The composite video signal supplied to the delay device 11 is timed with the separated color signal and is supplied to the subtractor 12. The color signal supplied via the switch 25 is subtracted from the composite video signal supplied to the subtractor 12, and the luminance signal is supplied to the output terminal 13.

The color signal supplied to the demodulation device 14 is demodulated into a color difference signal, and then amplified by the ACC device 15 so that the burst level becomes constant and supplied to the LPF 16. LP
The signal supplied to F16 is band-limited to 500 KHz and supplied to the modulator 17.

The horizontal synchronizing frequency (hereinafter referred to as f _H ) is extracted from the composite video signal supplied to the f _H separation device 20 and is supplied to the frequency multiplier 21 and the counter 22. F _H supplied to the frequency multiplier 21 is 160 multiplied, 160f _H is supplied to the counter 23. Counter 22 counts the supplied f _H, the 160f _H respectively, supplied to the ROM 24. The drum rotation pulse is supplied to the ROM 24 via the input terminal 26. R by the output of the counters 22 and 23 and the drum rotation pulse
The OM 24 is called up to obtain the processed 40 f _H square wave for recording color process processing and supply it to the modulator 17.

The band-limited color difference signal supplied to the modulator 17 is 40f _H (about 6) supplied from the ROM 24.
29 KHz) and is supplied to the LPF 18. LP
The signal supplied to F18 is band-limited so as to prevent interference with the FM-modulated luminance signal, and the low frequency conversion chroma signal subjected to the color process during recording is supplied to the output terminal 19.

Next, the input of the Y / C separate signal will be described. The separate SY signal is supplied to the delay device 11 via the 1H delay device 2. The switch 25 is switched so as to select the signal “0”, and the separate SY signal via the 1H delay device 2 is directly supplied to the output terminal 13 as a luminance signal.

The separate S-C signal is supplied via the input 9 and via the switch 10 and the 1H delay device 3.
Is supplied to the switch 8 via. The separate SC signal supplied to the switch 8 is supplied to the modulator 14 and processed in the same manner as when the NTSC composite video signal is input.

[0017]

As described in detail above, according to the present invention, the circuit configuration for extracting and processing color signals can be simplified, the performance is improved, the cost is reduced by reducing the hardware scale, and the cost performance is improved. Can be planned.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a color signal processing circuit according to the present invention.

FIG. 2 is a block diagram of a conventional color signal processing circuit.

[Explanation of symbols]

2, 3 ... 1H delay device, 4, 5, 6 ... Band pass filter, 7 ... 3-line dynamic comb filter, 11 ... Delay device, 14 ... Demodulation device, 15 ... ACC, 16, 18 ...
LPF, 17 ... modulator, 20 ... f _H separator, 21 ...
Multiplier, 22, 23 ... Counter, 24 ... ROM

Claims (1)

[Claims] 1. A composite video signal is supplied, means for outputting a demodulation signal that demodulates a color difference signal, low-pass conversion color subcarrier generation means for outputting a low-pass conversion color subcarrier, and the demodulation signal A color signal processing circuit comprising: a modulation unit that modulates with a low-frequency conversion color subcarrier and outputs a low-frequency conversion chroma signal.