JP3129108B2 - Video signal processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, with the development of media and the trend toward borderless TV systems in various parts of the world, there is a growing need to cope with the NTSC broadcasting system even in regions employing the PAL broadcasting system.

[0003] The following is a description of the PASC from the carrier color signal of the NTSC system.
A description will be given of a conventional video signal processing apparatus for converting into an L-type carrier color signal.

FIG. 6 shows an example of a conventional color signal conversion processing device. In FIG. 6, 19 is an input terminal, 37
Is a band pass filter (hereinafter abbreviated as BPF), 38 is an automatic gain control circuit (hereinafter abbreviated as ACC), 39 is a decoder circuit, 40 is a reference oscillator, 41 is a low pass filter (hereinafter abbreviated as LPF), 42 is LPF, 43 is a modulator, 44 is a modulator, 46 is a BY sub-carrier circuit, 47 is an RY sub-carrier circuit, 45 is a reference oscillator, 48 is a mixing circuit, 50 is a blank gate circuit, and 51 is an input terminal. , 53
Is a modulator, 52 is an input terminal, 49 is a phase control circuit, 54
Is a mixing circuit, and 55 is a BPF.

[0005] The operation of the color signal conversion processing device configured as described above will be described below. First, the NTSC video signal input to the input terminal 19 is
In the PF 37, the transport color signal is extracted. The amplitude of the carrier chrominance signal is controlled by the ACC 38 so that the color burst signal becomes a constant level, and is supplied to the decoder circuit 39. In the decoder circuit 39, the carrier chrominance signal is demodulated into two color difference signals of RY and BY using the output signal of the reference oscillator 40 synchronized in phase with the color burst signal of the carrier chrominance signal as a carrier. The BY color difference signal output from the decoder circuit 39 is supplied to the modulator 44 after removing unnecessary components in the LPF 42, and the RY color difference signal is supplied to the LPF 4
At 1, unnecessary components are removed and supplied to the modulator 43.
The modulator 44 converts the BY color difference signal into a reference oscillator 4
5 is modulated by the PAL system with the carrier created through the BY sub-carrier circuit 46 from the output of 5, and the modulated signal is supplied to the mixing circuit 48. The modulator 43 converts the RY color difference signal from the output of the reference oscillator 45 to the RY subcarrier circuit 4.
The signal is modulated to the PAL system by the carrier created through the step 7, and the modulated signal is supplied to the mixing circuit 48.

[0006] The mixing circuit 48 mixes the output signal of the modulator 44 and the output signal of the modulator 43 and supplies the mixed signal to the blank gate circuit 50. Blank gate circuit 5
At 0, the vertical blanking period and the horizontal blanking period are erased from the output signal of the mixing circuit 48 by the control signal of the input terminal 51, and the erased signal is supplied to the mixing circuit 54. On the other hand, in the modulator 53, the burst flag signal at the input terminal 52 is converted to
The signal is modulated into a color burst signal of the system and supplied to the mixing circuit 54. The phase control circuit 49 receives the output signal of the BY sub-carrier circuit 46 and the output signal of the RY sub-carrier circuit 47 as inputs and controls the phase of a carrier for modulating a PAL color burst signal. . Mixing circuit 54
Now, the output signal of the blank gate circuit 50 and the modulator 53
Are mixed and supplied to the BPF 55. BP
In F55, unnecessary components generated at the time of modulation are removed and PA
The transport color signal of the L system is extracted.

[0007]

However, the above conventional configuration has a problem that the circuit scale for converting the carrier color signal of the NTSC system to the carrier color signal of the PAL system becomes very large. Was.

The present invention solves the above-mentioned conventional problems. By using a color signal processing circuit for converting an NTSC carrier color signal having a PAL subcarrier frequency into a NTSC carrier color signal, the present invention can convert the NTSC carrier color signal when stopped. An object of the present invention is to convert the color signal into a PAL carrier color signal.

[0009]

In order to achieve this object, a video signal processing apparatus according to the present invention comprises a low-frequency conversion circuit for frequency-converting a carrier color signal of the NTSC system to a low frequency, and a reproduction from a head during reproduction. A switch circuit for selecting a signal and, when stopped, selecting an output signal of the low-frequency conversion circuit;
A reference oscillator having a subcarrier frequency substantially as an oscillation frequency, and an NTSC carrier having a PAL subcarrier frequency for converting a low-frequency conversion chrominance signal output from the switch circuit with reference to an output signal frequency of the reference oscillator. A color signal processing circuit that converts the output signal to a color signal; a multiplier that doubles the output signal frequency of the reference oscillator; and an output signal of the color signal processing circuit using the output signal of the multiplier.
It is constituted by a system conversion circuit for converting into a system carrier color signal.

[0010]

With this configuration, by using a chrominance signal processing circuit for converting an NTSC carrier color signal having a PAL subcarrier frequency into a NTSC carrier color signal, the NTSC carrier color signal can be converted to a PAL carrier color signal when stopped. A video signal processing device capable of streamlining circuits can be provided.

[0011]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. In FIG. 1, 1 is an input terminal, 2 is a switch circuit, 3 is an LPF, 4 is ACC, 5 is a balanced modulator, 6 is B
PF, 7 is a comb filter, 8 is a BPF, 9 is a reference oscillator, 10 is a balanced modulator, 11 is a selection circuit, 12 is 1/8.
A frequency divider, 13 is a voltage controlled oscillator (hereinafter abbreviated as VCO), 14 is an LPF, 15 is a phase comparator, 16 is a multiplier, 17 is a method conversion circuit, 18 is an output terminal, 19 is an input terminal, and 20 is A low-frequency conversion circuit, 21 is an input terminal, 22 is an input terminal, and 23 is a color signal processing circuit.

The operation of the video signal processing device configured as described above will be described with reference to FIG.

First, based on the output signal frequency of the reference oscillator 9, the low-frequency converted chrominance signal output from the switch circuit 2 is converted into an NTSC carrier color signal having a PAL sub-carrier frequency and output. The operation of the processing circuit 23 during reproduction will be described.

In the switch circuit 2, the reproduction signal of the input terminal 1 is selected by the control signal of the input terminal 21. From the reproduced signal, a reproduced low-frequency conversion color signal is extracted in the LPF 3. The amplitude of the reproduced low-frequency converted color signal is controlled in the ACC 4 so that the color burst signal becomes a constant level, and is supplied to the balanced modulator 5. The frequency conversion is performed by the balanced modulator 5, and unnecessary components generated at the time of balanced modulation in the BPF 6 are removed, and a reproduced carrier color signal is extracted.
Further, the adjacent crosstalk component is removed by the comb filter 7 to obtain a reproduced carrier color signal. Phase comparator 1
In step 5, the phase of the color burst signal of the carrier chrominance signal output from the comb filter 7 is compared with the phase of a reference signal from a reference oscillator 9 which oscillates at a subcarrier frequency (hereinafter abbreviated as fsc) of the PAL system. The error signal passes through the LPF 14 and controls the voltage-controlled oscillator 13 having a horizontal scanning frequency (hereinafter abbreviated as fH) of 320 times. This 320fHVCO
The oscillating frequency 13 is frequency-divided by に お い て in the ８ frequency divider 12, and four output signals having different phases by 90 degrees are supplied to the selection circuit 11. The selection circuit 11 selects four output signals from the 1/8 frequency divider 12 and supplies a carrier signal of the balanced modulator 10 according to the VHS standard of the NTSC system. The balanced modulator 10 performs balanced modulation with the reference signal from the reference oscillator 9, and removes unnecessary components with the BPF 8 to use the carrier as the carrier of the balanced modulator 5. With the above configuration, the carrier chrominance signal from the comb filter 7 is phase-locked to the oscillation frequency of the reference oscillator 9 and the subcarrier frequency is NTS, which is a PAL system.
This is a reproduction and transport color signal of the C system.

Next, when the carrier color signal of the NTSC system is stopped, the subcarrier frequency is set to the NTSC system of the PAL system.
A description will be given of a case of converting to a carrier color signal of a system.

First, an example of the low-frequency conversion circuit 20 will be described.
The operation will be described with reference to FIG. Input terminal 19
The NTSC video signal is input to the BPF 24 and the NTSC carrier color signal is extracted therefrom and supplied to the balanced modulator 25. This carrier chrominance signal is converted into a low-frequency conversion chrominance signal by a balanced modulator 25 using the output signal of a reference oscillator 26 having a frequency substantially equal to the sum of the NTSC subcarrier frequency and the low-frequency conversion subcarrier frequency as the oscillation frequency. The frequency is converted and output to the output terminal 27.

In FIG. 1, the output signal of the low-frequency conversion circuit 20 is supplied to a switch circuit 2. The switch circuit 2 selects an output signal of the low-frequency conversion circuit 20 based on a control signal of the input terminal 21 and supplies the output signal to the LPF 3. The following operation of the color signal processing circuit 23 is the same as that in the case where the switch circuit 2 selects the input terminal 1 side, and thus the description is omitted.

With the above configuration, NT
The conversion of the SC low-band conversion chrominance signal to the NTSC subcarrier frequency chrominance signal having the sub-carrier frequency of the PAL system can be shared when used during reproduction and when stopped.

A carrier color signal of the NTSC system is converted into a carrier color signal of the PAL system by the system conversion circuit 17. The difference between the carrier color signals of the PAL system and the NTSC system will be described with reference to the vector diagram of FIG. explain.

In FIG. 4, (1) is a carrier color signal of the NTSC system, in which the color signal vector is J. The phase of J is φ. K indicates a color burst signal. In the case of the color signal J, the state (1) remains in the NTSC system. On the other hand, the cases of the PAL system are shown in (2) and (3). In (2), the color signal B
Is the same as in the case of (1), except that the color burst signal is shifted by -45 degrees to L. (3) is obtained by inverting the vector of (2) with respect to the BY axis,
The color signal is at position N and the color burst signal is at position M. At this time, the RY axis is inverted. In the case of the carrier color signal of the PAL system, the vectors (2) and (3) are alternately repeated for each line.

Therefore, the carrier color signal of the NTSC system is
In the case of converting into the AL color signal, conversion from (1) to (2) and conversion from (1) to (3) are required. In the conversion from (1) to (2), only the color burst signal needs to be shifted by -45 degrees. In the conversion from (1) to (3), it is necessary to shift the color burst signal by +45 degrees and to invert the polarity of the RY axis of the color signal.

The multiplier 16 in FIG. 1 multiplies the fsc signal from the reference oscillator 9 and outputs a 2fsc signal. Next, in the system conversion circuit 17, the multiplier 1
6 from the carrier color signal of the NTSC system to the carrier color signal of the PAL system using the 2fsc signal output from
Will be output.

FIG. 3 shows an example of the system conversion circuit 17.
The operation will be described with reference to FIG. The 2fsc signal input to the input terminal 33 is phase-shifted by the first phase shifter 32 and becomes a carrier of the balanced modulator 31. The balanced modulator 31 receives the carrier color signal of the NTSC system input to the input terminal 28, and performs balanced modulation using the 2fsc signal from the first phase shifter as a carrier. Now, assuming that the carrier color signal of the NTSC system is the signal of (1) in FIG. 4, it can be expressed by (Equation 1).

[0025]

(Equation 1)

On the other hand, the carrier signal is represented by (Equation 2).

[0027]

(Equation 2)

By multiplying (Equation 1) and (Equation 2), (Equation 3) is obtained.

[0029]

(Equation 3)

(Equation 3) shows the output signal of the balanced modulator 31. If the LPF 34 removes the harmonic component and makes the level the same as the level of the input terminal 28, the output signal becomes the equation (Equation 4). Can be indicated by

[0031]

(Equation 4)

In equation (4), if θ = 0 degrees,

[0033]

(Equation 5)

(Equation 5) shows a signal whose phase polarity is inverted from that of (Equation 1). That is, by setting the phase shift amount of the first phase shifter 32 so that θ = 0 degrees, the LPF
Is a signal obtained by inverting the polarity of the phase of the carrier chrominance signal from the input terminal 28. The phase shifter 29 sets the phase to +4
The phase shifter 30 shifts the phase by −45 degrees. In the switch circuit 35, an input signal a of the input terminal 28, an output signal d of the LPF 34, an output signal b of the phase shifter 29, and an output signal c of the phase shifter 30 are selected by a control signal from the input terminal 36. 18 is output.

Hereinafter, NTSC in the switch circuit 35 will be described.
The operation of converting the carrier color signal of the PAL system into the carrier color signal of the PAL system will be described with reference to FIG. FIG. 5A shows NTSC.
2 shows two lines of the carrier color signal. The arrow on the color burst signal indicates the direction on the vector diagram.
The arrow on the color signal indicates the direction of the RY axis on the vector diagram. (2) of FIG. 5 shows a carrier color signal of the PAL system. To convert the (1) NTSC carrier color signal into the (2) PAL carrier color signal,
The color burst signal of the first line is shifted by -45 degrees in phase, and the color signal of the first line may be the same signal,
The color burst signal of the line has a phase shift of +45 degrees, and the color signal of the second line needs to invert the RY axis. That is, in the switch circuit 35, as shown in (3) of FIG. 5, the color burst signal period of the first line is c.
A except for the color burst signal period of the first line,
B may be selected for the color burst signal period of the second line, and d may be selected for periods other than the color burst signal period of the second line. Thereby, it is possible to convert from the NTSC system to the PAL system.

This system conversion circuit can be used both when used during reproduction and when used when stopped.

[0037]

As described above, the present invention uses the chrominance signal processing circuit and the system conversion circuit for converting to the NTSC system carrier chrominance signal having the sub-carrier frequency of the PAL system used at the time of reproduction of the video tape recorder even when stopped. By the way, N
The present invention has an excellent effect that a circuit for converting a TSC carrier color signal into a PAL carrier color signal can be greatly rationalized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a video signal processing device of the present invention.

FIG. 2 is a block diagram showing a low-frequency conversion circuit in the embodiment.

FIG. 3 is a block diagram showing a system conversion circuit according to the embodiment;

FIG. 4 is a vector diagram of carrier color signals of the NTSC system and the PAL system.

FIG. 5 is a schematic diagram for explaining an operation of converting an NTSC system to a PAL system carrier color signal in the embodiment.

FIG. 6 is a block diagram showing a conventional color signal conversion device.

[Explanation of symbols]

 2 Switch circuit 3 LPF 4 ACC 5 Balanced modulator 6 BPF 7 Comb filter 8 BPF 9 Reference oscillator 10 Balanced modulator 11 Selection circuit 12 1/8 frequency divider 13 320 fHVCO 14 LPF 15 Phase comparator 16 Multiplier 17 System conversion Circuit 20 Low frequency conversion circuit 23 Color signal processing circuit

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nohisa Mimura 1006 Kadoma, Kazuma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-59-103485 (JP, A) JP-A-3 -186091 (JP, A) JP-A-62-267903 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 9/00 H04N 9/43 H04N 9/79-11/24

Claims (2)

(57) [Claims] 1. A frequency-division-modulated luminance signal obtained by frequency-modulating a luminance signal and a low-frequency converted chrominance signal obtained by frequency-converting a carrier chrominance signal to a low frequency band are respectively frequency-division multiplexed and recorded and reproduced. Occasionally, a frequency modulated luminance signal is demodulated into a luminance signal, and the low-frequency conversion chrominance signal is inversely converted into a carrier chrominance signal. A conversion circuit, a switch circuit for selecting a reproduction signal from the head at the time of reproduction, and selecting an output signal of the low-frequency conversion circuit at the time of stop, a reference oscillator having a subcarrier frequency of the PAL system as an oscillation frequency, A chrominance signal processing circuit for converting the low-frequency conversion chrominance signal output from the switch circuit into an NTSC carrier chrominance signal having a PAL subcarrier frequency with reference to an output signal frequency of an oscillator, and outputting the chrominance signal; A frequency converter for doubling the output signal frequency of the reference oscillator; and a system conversion circuit for converting the output signal of the color signal processing circuit into a PAL carrier color signal using the output signal of the multiplier. Characteristic video signal processing device. 2. A low-pass conversion circuit comprising: a band-pass filter for extracting a carrier color signal from an NTSC composite video signal;
A reference oscillator having an oscillation frequency substantially equal to the sum of the TSC subcarrier frequency and the low-frequency converted subcarrier frequency; and a balanced modulator for performing balanced modulation of an output signal of the reference oscillator and an output signal of the band-pass filter. 2. The video signal processing device according to claim 1, wherein: