JPH0710109B2 - Color signal processor - Google Patents

Description

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

2. Description of the Related Art The conventional color signal processing method used in consumer video tape recorders is a color conversion method in which a carrier color signal is frequency-converted into a low-frequency carrier color signal and recorded, and then is frequency-converted again into a carrier color signal during reproduction. This is a method called under.

FIG. 2 shows an example of a conventional color under reproduction system. In FIG. 2, the reproduction signal input from the input terminal 1 is a low pass filter (hereinafter referred to as LPF).
In step 2, the reproduced low frequency carrier color signal is extracted. The reproduced low-frequency carrier color signal that has been taken out is frequency-converted into a carrier color signal through the balanced modulator 3, and a bandpass filter (hereinafter BP
An undesired component generated at the time of balanced modulation is removed by (F) 4 and crosstalk from an adjacent track is removed by a comb filter 5 and output from an output terminal 6. On the other hand, the burst gate 7 extracts the burst portion of the output signal, and the phase comparator 9 compares the phase with the output signal of the reference oscillator 8. The phase error passes through the LPF 11 and the adder 12, and the center frequency is 8 _S (where _S is the low frequency sub-carrier frequency. In the case of VHS NTSC, _S = 40 _H : _H is the horizontal frequency). Voltage controlled oscillator (hereinafter referred to as VCO) 1
Control 3 The output of the VCO 13 passes through the 1/8 frequency divider 14 and the phase shift circuit 15, is multiplied by the signal frequency of the reference oscillator 8 in the balanced modulator 16, passes through the BPF 17, and is balanced by the balanced modulator 3.
Become a career of. In this way, the output burst signal is always synchronized with the reference oscillation.
trol) It becomes a loop. By the way, as a characteristic of the APC loop, there is a side lock phenomenon that the oscillation frequency of the VCO 13 is stable even at 8 ( _S ± _H ). Therefore, as a means for preventing the side lock phenomenon, the reproduced signal inputted from the input terminal 1 is passed through the luminance signal demodulator 18 to be demodulated into a luminance signal, and the synchronizing signal separating circuit 19 separates the synchronizing signal to separate the synchronized signal. Horizontal separation circuit that removes vertical sync signal and equalization pulse from the signal and only horizontal sync signal
In step 20, the first detection circuit 21 detects that the period is 4H, based on the extracted horizontal synchronizing signal. Furthermore, in the counter 22 during the above 4H period
The output signal of VCO13 is counted as a clock, the count number is decoded in the second decoder 27, and the VHS NTS
In the case of the C method, the control signal is not output in the range of 1276 to 1284, the control signal is output to increase the oscillation frequency of the VCO when the value is 1275 or lower, and the frequency is decreased when the value is 1285 or higher.The control signal is LPF25, It controls the VCO 13 through the adder 12. In this way, the oscillation frequency of VCO13 is 8 _S ± 4
It is restricted so as not to shift more than _H.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the configuration as described above, when the reproduction signal is not input, the output of the synchronization signal separation circuit 19 is in a state of generating a constant level or a lot of noise, The horizontal separation circuit 20 will generate a pulse having a constant level or a cycle shorter than the original 1H. The detection circuit 21 detects the 4H period based on the horizontal sync signal from the horizontal separation circuit 20, but the horizontal sync signal output from the horizontal separation circuit 20 is not output for a certain period or is shorter than the original 1H. When the pulse has a paddle cycle, the period detected by the first detection circuit 21 is longer or shorter than the original 4H period. If the period detected by the first detection circuit 21 is longer than the original 4H period, the counter 22
Since the number of counts is larger than 1284, the second decoder 27 outputs a control signal to lower the oscillation frequency of the VCO 13. Conversely, if it is shorter than the original 4H period, VC
It is controlled to raise the oscillation frequency of O13. Therefore,
If the videotape recorder is in stop mode or playing an unrecorded part of the tape, VCO1
The oscillation frequency of 3 is maintained at the upper or lower limit frequency. Therefore, when the stop mode is changed to the reproduction mode, or when the unrecorded portion of the tape is changed to the recorded portion, the regular 4H period is detected by the regular horizontal synchronizing signal, and the counter 22 and the second decoder 27 By work, VCO1
Since 3 is controlled to the oscillation frequency of 8 _{S and} the APC loop then works, it takes time to pull in the APC loop.
Therefore, on the television screen, the phenomenon that the brightness first appears and then the color appears with a slight delay, which causes a discomfort to the user.

Also, in special playback, when the head is tracing tracks with different azimuths, there is no playback signal, so the oscillation frequency of VCO13 is controlled up or down, and after that, the VCO1 shifts to the track with the same azimuth and then VCO1.
3 is controlled to 8 _S , and then the APC loop works, so APC
It takes time for the loop to pull in. Therefore, the special reproduction screen has a drawback that a state in which no color is added or a state in which color is added or disappeared appears.

In view of the above problems, the present invention provides a color signal processing device in which the APC loop is pulled in at a high speed when a reproduced signal changes from a no-input state to an input state.

Means for Solving the Problems In order to solve the above problems, the color signal processing device of the present invention oscillates at a center frequency that is an integral multiple of the low-frequency subcarrier, and outputs an output signal from the low-frequency carrier color signal to the carrier color. A voltage controlled oscillator used to create a converted carrier signal for converting into a signal; a first detection circuit for detecting a predetermined horizontal period by a horizontal synchronization signal; A counter that counts the output signal of the voltage controlled oscillator as a clock, and outputs a detection signal when the count number of the counter in the predetermined horizontal period is less than or equal to a first predetermined number and greater than or equal to a second predetermined number A second detection circuit, a reference voltage source whose output voltage is a control voltage oscillated at the center frequency of the voltage controlled oscillator, a reference oscillator oscillated at a subcarrier frequency, and a reproduction carrier. A phase comparator that compares the phase of a color burst signal of a color sending signal with a signal from the reference oscillator, and a voltage control unit of the voltage controlled oscillator when the second detection circuit detects the detection signal. A switch for connecting the voltage control unit of the voltage controlled oscillator to the phase comparator when the second detection circuit is not detecting a detection signal, the switch being connected to a reference voltage source; and the switch in the predetermined horizontal period. When the count number of the counter is less than or equal to the first predetermined number, the output signal for controlling the oscillation frequency of the voltage controlled oscillator is not output, and the output signal is larger than the first predetermined number and larger than the third predetermined number. If it is smaller, an output signal for controlling to raise the oscillation frequency of the voltage controlled oscillator is output to the voltage control unit of the voltage controlled oscillator, and the output signal is not less than the third predetermined number and not more than the fourth predetermined number. To When the output signal for controlling the oscillation frequency of the voltage controlled oscillator is not output and is larger than the fourth predetermined number and smaller than the second predetermined number, the oscillation frequency of the voltage controlled oscillator is lowered. An output signal to be controlled is output to the voltage control unit of the voltage controlled oscillator,
When the number is equal to or more than the predetermined number, the output signal for controlling the oscillation frequency of the voltage controlled oscillator is not output.

Effect The present invention has the above-described configuration, and when the count number of the counter is less than or equal to the first predetermined number and greater than or equal to the second predetermined number, the oscillation frequency of the VCO is set to the center frequency to reproduce. Even when there is no signal, the detection circuit detects VC other than the original predetermined horizontal period
Since O becomes the center frequency, it is possible to speed up the pulling of the APC loop when there is no reproduction signal and when there is a reproduction signal.

Embodiment Hereinafter, a color signal processing device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a video signal processing device according to an embodiment of the present invention.

It should be noted that, in the present embodiment, the description will be limited to the NTSC system.

The difference from this embodiment and the conventional example of FIG. 2 is that a first decoder is provided instead of the second decoder, and a second detection circuit 23, a switch 10 and a reference voltage source 26 are newly provided. is there. Other functions are similar to those described with reference to FIG. First
The following table shows the output signals output from the second detection circuit 23 and the first decoder 24 according to the count number counted by the counter 22 during the 4H period detected by the detection circuit 21 of FIG.

Here, it is assumed that the oscillation frequency of the VCO 13 decreases as the control voltage increases, and conversely increases as the control voltage decreases. The switch 10 is connected to the reference voltage source 26 when the output of the second detection circuit 23 is at the Hi level, and is connected to the phase comparator 9 when the output is at the Lo level. Furthermore, the oscillation frequency of the VCO 13 when the switch 10 is connected to the reference voltage source 26 is 8 _S (320
_H ).

Now, when the count number of the counter 22 is 1150 or less or 1401 or more, the output of the second detection circuit 23 becomes Hi level, so the reference voltage source 26 is connected by the switch 10 and VCO1
3 is the center frequency. When the number of counts is 1151 to 1276, the output of the first decoder is Lo level. LPF25
Since the response of is slow, the oscillation frequency of VCO gradually increases. When the count number is between 1277 and 1284, the output of the first decoder becomes high impedance, so the VCO 13 is controlled by the error voltage from the phase comparator 9, and the second detection circuit 23 and the first decoder 24 Has no control. The first decoder for counts from 1285 to 1400
Since 24 becomes Hi level, the VCO 13 is controlled to gradually reduce the oscillation frequency. When the count number is 1401 or more, the second detection circuit 23 becomes Hi level, and the VCO 13 oscillates at the center frequency. The difference from the conventional example shown in FIG.
Since there is no control by the second detection circuit 23 and the output of the second decoder is Lo level when it is 1150 or less and Hi level when it is 1401 or more, the output of the first decoder becomes high impedance. is there.

If there is no reproduced signal, the first detection circuit
21 cannot detect the regular 4H period, and the counter 22 counts 1500 or less or 1401 or more. At this time, by setting the VCO 13 at the center frequency, the state where there is no reproduction signal is changed to a certain state, and when the first detection circuit detects the regular 4H period, the count number of the counter 22 is The states of 1277 to 1284 are entered, and the VCO 13 is immediately controlled only by the error signal of the phase comparator 9, so that the APC loop can be speeded up.

As described above, according to the present embodiment, in order to generate a converted carrier signal that oscillates at a center frequency that is eight times as high as the low-frequency subcarrier and the output signal is converted from the low-frequency carrier color signal to the carrier color signal. A VCO 13 used, a first detection circuit 21 that detects a 4H period by a horizontal synchronization signal, and a counter 22 that counts the output signal of the VCO 13 as a clock during a 4H period detected by the first detection circuit 21. , The second detection circuit 23 that outputs a detection signal when the count number of the counter 22 in the 4H period is 1150 or less and 1401 or more
A reference voltage source 26 having a control voltage oscillated at a center frequency of the VCO 13 as an output voltage, a reference oscillator 8 oscillated at a subcarrier frequency, a color burst signal of a reproduction carrier color signal, and a signal from the reference oscillator 8. Comparator 9 for comparing the phases of
When the second detection circuit 23 detects a detection signal, the voltage control unit of the VCO 13 is connected to the reference voltage source 26,
If the detection circuit 23 of is not detecting the detection signal, VCO1
A switch 10 for connecting the voltage control unit 3 to the phase comparator 9.
When the count number of the counter 22 in the 4H period is 1150 or less, the output signal for controlling the oscillation frequency of the VCO 13 is not output, and when it is greater than 1150 and less than 1277, the oscillation frequency of the VCO 13 is increased. Output signal to control the voltage of VCO13 to 1277 or more and 1284
In the above cases, the output signal for controlling the oscillation frequency of VCO13 is not output, and when it is larger than 1284 and smaller than 1401, the output signal for controlling the oscillation frequency of VCO13 is reduced to the voltage control unit of VCO13. By providing the first decoder 24 which outputs and outputs the output signal for controlling the oscillation frequency of the VCO 13 in the case of 1401 or more, the APC when the reproduction signal shifts from the no-input state to the input state
The loop pull-in time can be shortened.

As described above, the present invention is a recording / reproducing apparatus such as a video tape recorder that converts a carrier color signal into a low-frequency carrier color signal for recording, and reversely converts the carrier color signal during reproduction. A voltage-controlled oscillator that oscillates at a center frequency that is an integral multiple of the sub-carrier and that is used to create a converted carrier signal for converting the output signal from the low-frequency carrier color signal to the carrier color signal Detection circuit for detecting that the output signal of the voltage controlled oscillator is used as a clock during the predetermined horizontal period, and the count number of the counter during the predetermined horizontal period is A second detection circuit that outputs a detection signal when the number is equal to or less than a predetermined number of 1 and when the number is equal to or more than a second predetermined number; A reference voltage source as an output voltage, a reference oscillator that oscillates at a subcarrier frequency, a phase comparator that compares the color burst signal of the reproduction carrier color signal with the signal from the reference oscillator, and the second detection When the circuit detects the detection signal, the voltage control unit of the voltage controlled oscillator is connected to the reference voltage source, and when the second detection circuit does not detect the detection signal, the voltage controlled oscillator A switch that connects a voltage control unit to the phase comparator, and an output that controls the oscillation frequency of the voltage controlled oscillator when the count number of the counter in the predetermined horizontal period is less than or equal to the first predetermined number. If the signal is not output and is larger than the first predetermined number and smaller than the third predetermined number, the output signal for controlling to raise the oscillation frequency of the voltage controlled oscillator is the voltage controlled oscillation. The output to the voltage control unit, in the case of less than a predetermined number of said third and fourth more than a predetermined number,
When the output signal for controlling the oscillation frequency of the voltage controlled oscillator is not output and is larger than the fourth predetermined number and smaller than the second predetermined number, control is performed to lower the oscillation frequency of the voltage controlled oscillator. A decoder for outputting an output signal for controlling the oscillation frequency of the voltage controlled oscillator to the voltage control unit of the voltage controlled oscillator, and when the second predetermined number or more is output. This makes it possible to speed up the pull-in time of the APC loop when the playback signal goes from the no-input state to the input state.For example, when the playback signal goes from the stop state to the playback state or from the unrecorded part of the video tape. When moving to the recording part, or when the head moves the trace location from a track with different azimuth to a track part with the same azimuth. Coloring on the television screen, the excellent effect of being able to produce about the same time as the luminance signal is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a color signal processing device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional color signal processing device. 1 ... Input terminal, 2 ... LPF, 3 ... Balanced modulator, 4 ...
... BPF, 5 ... comb filter, 6 ... output terminal, 7 ...
... Burst gate, 8 ... Reference oscillator, 9 ... Phase comparator, 10 ... Switch, 11 ... LPF, 12 ... Adder, 13 ...
… VCO, 14 …… 1/8 divider, 15 …… Phase shift circuit, 16…
Balanced modulator, 17 BPF, 18 Luminance signal demodulator, 19
...... Sync signal separation circuit, 20 ...... Horizontal separation circuit, 21 ...... First detection circuit, 22 ...... Counter, 23 ...... Second detection circuit, 24 ...... First decoder, 25 ...... LPF, 26 …… Reference voltage source.

Claims (1)

[Claims] 1. A recording / reproducing apparatus for converting a carrier color signal into a low-frequency carrier color signal for recording, and for converting it back into a carrier color signal at the time of reproduction, which oscillates at a center frequency which is an integral multiple of a low-frequency subcarrier. ,
A voltage controlled oscillator used to create a converted carrier signal for converting an output signal from a low-frequency carrier color signal to a carrier color signal, and a first horizontal position detecting signal for detecting a predetermined horizontal period by a horizontal synchronization signal. A detection circuit; a counter that counts the output signal of the voltage controlled oscillator as a clock during the predetermined horizontal period; a count number of the counter during the predetermined horizontal period that is less than or equal to a first predetermined number; A second detection circuit that outputs a detection signal when the number is equal to or more than a predetermined number, and a reference voltage source that uses a control voltage oscillated at the center frequency by the voltage controlled oscillator as an output voltage.
The reference oscillator that oscillates at the subcarrier frequency, the phase comparator that compares the phase of the color burst signal of the reproduction carrier color signal with the signal from the reference oscillator, and the second detection circuit detects the detection signal. In this case, the voltage control unit of the voltage controlled oscillator is connected to the reference voltage source, and the voltage control unit of the voltage controlled oscillator is connected to the phase comparator when the second detection circuit does not detect the detection signal. When the connected switch and the count number of the counter in the predetermined horizontal period are less than or equal to the first predetermined number, the output signal for controlling the oscillation frequency of the voltage controlled oscillator is not output,
When it is larger than the first predetermined number and smaller than the third predetermined number, an output signal for controlling to increase the oscillation frequency of the voltage controlled oscillator is output to the voltage control unit of the voltage controlled oscillator, 3 or more and a fourth predetermined number or less, the output signal for controlling the oscillation frequency of the voltage controlled oscillator is not output, and the output signal is larger than the fourth predetermined number and the second predetermined number. If it is smaller, an output signal for controlling the oscillation frequency of the voltage controlled oscillator is output to the voltage control unit of the voltage controlled oscillator, and if it is the second predetermined number or more, the voltage controlled oscillator is output. A color signal processing device, comprising: a decoder that does not output an output signal that controls the oscillation frequency of the color signal processing device.