JPS59172898A - Clock pulse generating circuit in color video signal reproducing device - Google Patents

Abstract

PURPOSE:To prevent color blurring by expanding time axis of a reproducing time axis compression luminance signal and a reproducing time axis compressing line sequential color difference signal from a same timing position as that at the time axis compression respectively even if a reproducing time axis fluctuation is included in a reproduced H signal. CONSTITUTION:A pulse in following low reproducing time axis fluctuation of the reproduced H signal extracted from a voltage controlled oscillator 42 in the 1st phase locked loop PLL39 is impressed to a monostable multivibrator 44 constituting a delay circuit. The amount of delay is controlled by output signal of a loop filter 41 for the monostable multivibrator 44. Then, an output delay pulse from the monostable multivibrator 44 is applied to a phase comparator 46 constituting the 2nd PLL45, and after the phase is compared with the phase of a signal from a counter 50, the result is given to a voltage controlled oscillator 48. The clock signal is fed to a latch circuit from terminals 51, 54 and 55 via counters 49, 52 and 53 respectively. Thus, the time axis of the time axis compressing luminance signal and the time axis compressing line sequential color difference signal is expanded respectively in the same timing as that at the time axis compression.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a clock pulse generation circuit in a color video signal reproducing device, in which a luminance signal and a line-sequential color difference signal are greatly compressed in time axis, and the two signals are time-divided. The present invention relates to a circuit that tracks low-frequency reproduction time axis fluctuations and generates clock pulses without phase errors in an apparatus for reproducing a recording medium (for example, a magnetic tape) on which multiplexed recording is performed.

Prior Art Current color video signal recording/reproducing device (e.g. VTR)
The mainstream recording and reproducing devices in Noura are standard format (NTS)
A luminance signal and a low-frequency conversion carrier color signal are separated from a composite color video signal (C system, P'AL system, or SECAM system), and the brightness signal is frequency-modulated to become a frequency-modulated wave, and the carrier color signal is After converting the frequency into a low frequency carrier color signal, the frequency-modulated wave is frequency-division multiplexed and recorded, and during playback, signal processing is performed in the opposite manner to that during recording to comply with the original standard method. It is well known that this is a recording and reproducing apparatus using a so-called low-frequency conversion recording and reproducing method, which obtains a reproduced composite color video signal. A recording and reproducing device using such a low-frequency conversion recording and reproducing method is: (1) Since the band of the luminance signal can be arbitrarily selected, the band that can be recorded and reproduced is relatively narrow.
The demodulated color signal is not easily affected by fluctuations in the reproduction time axis of the VTR, and ■ Only the luminance signal passes through the FM modulation and demodulation system, and the pilot signal is not recorded or reproduced, so there is no possibility of beat interference. Furthermore, it has the following advantages: (1) The frequency-modulated luminance signal acts like a high-frequency bias, and the carrier color signal can be recorded with good linearity.

However, on the other hand, recording and reproducing devices using the above-mentioned low frequency conversion recording and reproducing method are somewhat insufficient in achieving higher image quality due to the limited recording and reproducing bands for luminance signals and carrier color signals; Range conversion carrier color signal is NTSC system or P'AL
When recording a color video signal, a balanced modulation wave is used, and due to uneven contact between the tape and head, AM noise in the reproduced low-frequency conversion carrier color signal occurs, deteriorating the S/N (signal-to-noise ratio), and In a recording and reproducing apparatus that uses the so-called azimuth recording and reproducing method, in which two heads that record and reproduce adjacent video tracks are set at different azimuth angles to record and form video tracks without guard bands, the azimuth loss effect occurs. Since the low frequency conversion is insufficient for low frequency, the low frequency conversion carrier color signal of the adjacent track will be mixed into the playback signal as a crosstalk component. The phase of the color subcarrier frequency of the carrier color signal is changed over one horizontal scanning period (11
−1), or approximately 90° for each period (for example,
9073, Japanese Patent Publication No. 55-32273), or crosstalk countermeasure processing is required, such as inverting the phase of only the low-frequency conversion carrier color signal of one of the adjacent video tracks every 111 steps. There was a problem.

Furthermore, although it is not possible to record and reproduce SECAM color video signals using the above-mentioned azimuth recording and reproducing apparatus, horizontal synchronization is required in the direction perpendicular to the longitudinal direction (track width direction) of adjacent video tracks. The signal recording positions are aligned and recorded (so-called H-aligned recording), and the modulation signal components of the low-pass conversion carrier color signal, which is the frequency-modulated wave, are approximately the same, that is, the color difference signal components of the same type are ) and then play it back, the frequency reproduced as crosstalk from the adjacent track of the above low frequency conversion carrier color signal has no correlation with the color video signal component at one field interval. Moreover, since the modulation signal components with almost the same modulation signal components are recorded side by side, the frequency is approximately the same as the frequency of the low-frequency conversion carrier color signal of the playback track, and the beats generated by both signals have a frequency close to zero. Therefore, there is almost no effect of crosstalk.

However, when reproducing a magnetic tape with a track pattern in which no 5FCA'M of adjacent tracks are recorded,
Because the carrier frequencies of the low frequency conversion carrier color signals in the system are different, the beat frequency due to crosstalk from adjacent tracks extends to the high frequency range, which appears as noise on the playback television screen. There was a problem in that the recording/reproducing method could not be applied.

On the other hand, recent dramatic advances in semiconductor technology, precision processing technology, and small component technology have made it possible to improve the image quality of recording and reproducing devices and to make the devices smaller and lighter. Reducing the cassette size and drum diameter has a major impact on reducing the size and weight of the device, and in order to secure the necessary recording time for the small force cera 1~, it is necessary to slow down the tape running speed. In order to obtain high image quality in such a compact and lightweight recording and reproducing apparatus, a new recording and reproducing method other than the above-mentioned low frequency conversion recording and reproducing method has come to be required.

Therefore, various recording and reproducing methods have been proposed to meet the above requirements, and one of them is
Two types of color difference signals obtained by M demodulation are compressed in time axis, and a luminance signal is also compressed in time axis, these signals are time division multiplexed, this time division multiplexed signal is frequency modulated and recorded on a recording medium, There was a recording/playback device configured to perform signal processing in the opposite direction to that during recording to obtain a playback output of the original standard color video signal (for example, see Japanese Patent Laid-Open No. 53-5926). . This recording/reproducing device takes into consideration the difference between the bands of the luminance signal and the color difference signal, and transmits the color difference signal, which is a signal with a narrower band, within the horizontal blanking period. The color difference signal transmitted within the period is compressed in the time axis to about 20% of the 1H period, and the luminance signal is compressed in the same band as the time axis compressed color difference signal, which is advantageous from the viewpoint of bandwidth utilization. The two color difference signals are time-division multiplexed as line-sequential signals that are transmitted alternately every 11", and this signal is feed the modulator,
The output signal of this FM modulator is recorded on a magnetic tape, etc., and during playback, signal processing is performed in the opposite direction to that during recording to obtain a reproduced color video signal (hereinafter referred to as the timeplex method). ).

According to the time-plex method for transmitting such time-division multiplexed signals, there is no period during which the luminance signal and the color difference signal are transmitted simultaneously, so it is not possible to transmit the luminance signal and the carrier color signal as in the case of NTSC or PAL color video signals. Mutual interference between the luminance signal and the color difference signal, which can occur when transmitting them by band-sharing multiplexing, does not occur, and also in the case of NTSC, PAL, and SECAM color video signals. Even if a recording/reproducing device using the azimuth recording/reproducing method records and reproduces data on tracks that are not arranged in H order, the time-division multiplexed signal on adjacent tracks is frequency-modulated with a high-frequency carrier wave that has a large azimuth loss effect. Since the resulting frequency-modulated wave signal is recorded in the form of a frequency-modulated wave signal, almost no crosstalk occurs due to the azimuth loss effect, and the above-mentioned crosstalk countermeasures are unnecessary, and high-quality reproduced images can be obtained.

Furthermore, both the time-domain compressed luminance signal and the time-domain compressed color difference signal in the time-plex method have an energy distribution in which the energy is large in the low frequency band and small in the high frequency band, which makes it difficult for frequency modulation. Since it is a suitable signal format, it is possible to obtain a large modulation index and greatly improve the S/N ratio, and when the time axis is expanded, it is possible to almost completely eliminate reproduction time axis fluctuations, and from the above, reproduction The image quality can be significantly improved compared to that of the low-frequency conversion recording and reproducing method.

In such a timeplex recording and reproducing device,
The control pulse generator 7 is provided with a clock pulse generator circuit for generating clock pulses that are phase-synchronized with the horizontal synchronizing signal, and this clock pulse generator circuit is normally a phase-locked loop (PLL).
).

Problems to be Solved by the Invention However, during reproduction, the reproduced horizontal synchronizing signal supplied to the clock pulse generation circuit usually contains noise, and this noise causes the output clock pulse to become less than the reproduced horizontal synchronizing signal. There were times when the phase could not be synchronized. This clock pulse is used as a clock pulse for time axis expansion of the reproduced time-axis compressed luminance signal and the time-axis compressed line-sequential color difference signal, so if the phase of the clock pulse is not synchronized with the phase of the reproduced horizontal synchronization signal, the time When the axis is expanded, the start position where the time axis is compressed is expanded from a different position, which causes problems such as color shift.

Therefore, the present invention provides a first phase signal having a response characteristic that follows the low frequency playback time axis fluctuation of the playback horizontal synchronization signal.
The output signal of the locked loop is supplied to a second phase-locked loop through a delay circuit for phase error compensation, and the second phase-locked loop generates and outputs a clock pulse of a desired repetition frequency. Therefore, it is an object of the present invention to provide a clock pulse generation circuit for a color video signal reproducing device that solves the above-mentioned problems.

Means for Solving the Problems The present invention provides two types of time-axis compressed color difference signals that are transmitted alternately every horizontal scanning period, and that - within one horizontal scanning period, the time-axis compressed color difference signals of - A time division multiplexed signal obtained by time division multiplexing together with an axial compressed luminance signal and a horizontal synchronization signal is modulated and recorded on a recording medium, and the reproduced horizontal signal in the reproduced time division multiplexed signal obtained by demodulating the reproduced signal is reproduced. A synchronization signal is supplied, and based on the clock pulse synchronized with the phase thereof, the time axis compressed luminance signal and the two types of time axis color difference signals in the reproduced time division multiplexed signal are converted to their original time axis using a memory. A clock pulse generation circuit for a color video signal reproducing device which obtains a reproduced standard color video signal from a reproduced luminance signal and two types of color difference signals obtained thereby, the clock pulse generating circuit being provided with the reproduced horizontal synchronizing signal and receiving the reproduced horizontal synchronizing signal. A first phase-locked loop having a response characteristic that follows the low-frequency playback time axis variation of the playback horizontal synchronization signal, and a delay amount variable by the output signal of a loop filter within the first phase-locked loop. a delay circuit that is controlled and outputs a delayed output signal of the voltage controlled oscillator in the first phase-locked loop; and the output signal of the delay circuit is supplied to generate a clock pulse of a desired repetition frequency. The second phase-locked loop outputs the output signal, and one embodiment thereof will be described below with reference to the drawings.

Embodiment FIG. 1 shows a patent application (name of invention [
A block system diagram of an example of a recording and reproducing apparatus disclosed by Color Video Signal Recording and Reproducing Apparatus] is not shown. First, to explain the operation at the time of recording, in FIG. is fed to a low-pass filter 3 through which the luminance signal is separated and fed to a decoder 4. The decoder 4 uses a bandpass filter (not shown) to convert the SFC
The carrier color signal, which is a frequency modulated wave, is separated and extracted from the AM color video signal, and is passed through a bell filter and an FM demodulator (both not shown) to produce a color difference signal (R-Y
) and (BY) are synthesized alternately in time series every 1H to obtain a line-sequential color difference signal as shown in FIG. 2(B).

This line-sequential color difference signal is based on the DC level b1 of the achromatic part (non-modulated carrier part) with a width of 4 to 9 μs on the back porch within the 1H period in which the color difference signal (B-Y) is transmitted, and the color difference signal (R- There is a fixed value difference from the DC level b2 of the achromatic color portion (non-modulated Kyrelia portion) of 4 to 9 μs width on the back porch within the next 11-1 period in which Y) is transmitted. This means that the color subcarrier frequency of the carrier color signal is the color difference signal (
B-Y) transmission line is 4.25 MH2, color difference signal 1
This is because the transmission line (RY) has a different frequency of 4.406 MHz. The line sequential color difference signals are subjected to DC level shifting so that the DC level of the achromatic color portion of one color difference signal matches that of the other color difference signal, and then supplied to the AD converter 14 through the switch circuit 13.

On the other hand, a luminance signal separated from the input SECAM color video signal is extracted from the low-pass filter 3, and a synchronization signal is separated and extracted from this luminance signal by a synchronization separation circuit 6, while an analog signal is extracted by an AD converter 5. After being digitally converted, they are supplied to random access memories (RAM) 8 and 9, respectively. Control pulse generator 7
is supplied with a synchronization signal from the synchronization separation circuit 6, and is supplied with the rectangular wave as a color difference signal discrimination pulse.
Converters 5, 14. It supplies the control pulses generated to the DA converters 11 and 16, generates horizontal synchronizing signals and various pulses with a width of about 4 μs, and also supplies the RAMs 8.9 and 1.
5, a write clock and a read clock are generated at predetermined timings and at a predetermined repetition frequency.

1. That is, the control pulse generator 7 supplies, for example, a write clock pulse of 8MH7 to one of the RAMs 8 and 9 to write the IH luminance signal transmitted in the video period of 52 μs into one of the RAMs, At the same time, for example, a 10MHz read clock pulse is applied to the
Only the period excluding the serial transmission period of the horizontal synchronization signal and the time axis compressed color difference signal of 111 minutes, which will be described later, is 1 day 52
Immediately after the transmission of the time-base compressed color difference signal (μs) is completed, it is supplied to the RAM of the user, and the luminance signal of 1 to 1 minute from the previous day stored in the RAM of the user is read out. This RAM8
The read operation and write operation of RAMs 8 and 9 are alternately switched every 1], and the switch circuit 10 on the output side of RAMs 8 and 9 performs the read operation by a control pulse from the control pulse generator 7. Since the output signal of the side RAM 8 or 9 is selectively output, the luminance signal compressed in time axis to 415 is intermittently taken out from the switch circuit 10 without any loss of information as shown in FIG. 2(E). . This time-base compressed luminance signal is digital-to-analog converted by a DA converter 11 and supplied to a switch circuit 12 .

In use, the line-sequential color difference signal output from the switch circuit 13 is converted into a rhiano-digital signal by the AD converter 1/I and then supplied to the RΔM 15.

RAM15 is 52μs in 1)-I(-64zzs)
The line-sequential color difference signal transmitted during the video period is written by a write clock pulse of, for example, 2 MHz from the control pulse generator 7, and after a certain period of time (for example, 1.6 μs) after the writing is completed, the read clock of IOMH2 is applied. The color difference signal whose time axis is compressed to 115 times is read and output by the pulse (therefore, one readout period is 1
0.4 μs) The switch circuit 12 is as shown in FIG.
A time-axis compressed line sequential color difference signal with a waveform as shown in C), and D
A time-base compressed luminance signal with a waveform as shown in FIG. 2 ([) taken out from the A converter 11 and a signal of about 4μ taken out from the control pulse generator 7 as shown in FIG. 2 (D).
Switching control is performed to time-division multiplex the s-width horizontal synchronization signals based on the output control pulses of the device 7, respectively. The time-division multiplexed signal taken out from this switch circuit 12 is supplied to the discrimination burst signal adding circuit 18, where it is generated by the discrimination pulse 1-signal generation circuit 17 based on the output control pulse of the control pulse generator 7. A burst signal for discrimination is added. This discrimination burst signal is a color difference signal (13-Y)
This is a burst signal for discriminating the transmission lines of (B-Y) and (R-Y), for example, a single frequency signal of about 1.5Mflz is used to identify the color difference signal S (B-Y) or (R-Y). The signal is generated only on the transmission line R-Y (in this case) in correspondence with the generation period of the horizontal synchronizing signal, as shown in FIG. 2(F).

In this way, the input terminals 1 and 2 (A) and 3 of FIG.
When a SECAM color video signal such as the color par signal shown in FIG.
A discrimination burst signal is superimposed on the horizontal synchronization signal every (=64 μs), and the horizontal synchronization signal and color reference level (
(the DC level of the achromatic part of the color difference signal -) and one of the time axis compressed color difference signal (R-Y)c or (B-Y)c,
The time-domain compressed luminance signal is time-division multiplexed, and the time-domain compressed color difference signal is extracted as a time-division multiplexed signal that is transmitted line-sequentially. The time-division multiplexed signal with the waveform shown in FIG. 3(B) includes one pre-emphasis circuit, 20 white peak level clip circuits. Clamp circuit 21. F
The M modulator 22 is supplied to the recording head 25 through a recording multiplication processing circuit known in the art in a VTR, consisting of a high-pass filter 23 and a recording amplifier 24.
recorded in

Next, the operation during reproduction will be described. At this time, the switch circuits 2 and 13 are respectively connected to the terminal P side. The time division multiplexed signal recorded on the magnetic tape 26 in the form of a frequency modulated wave is reproduced by the reproducing head 27.
This reproduced frequency modulated wave is transmitted to the regenerative amplifier 28. Equalizer 29. High pass filter 30. The signal is passed through a known reproduction signal processing circuit consisting of an FM demodulator 31 and a deennoassist circuit 32 to produce a reproduction time division multiplexed signal as shown in FIG. 3(B). This reproduced time division multiplexed signal passes through a switch circuit 2 and a low-pass filter 3 connected to a terminal P, respectively, to an AD converter 5. Synchronous separation circuit 62 determination burst signal detector 3
3, and is also supplied to the AD converter 14 through the switch circuit 13 connected to the terminal P.

AD converter 5, RAM8 and 9. A circuit section including a switch circuit 10 and a DA converter 11 generates a reproduced luminance signal whose time axis has been expanded and returned to the original time axis based on the output signal of the control pulse generator 7. here,
When one of the RAMs 8 and 9 is performing a write operation on the time axis compressed luminance signal of the reproduction time division multiplexed signal, the other one is performing a read operation, and the RAMs 8 and 9 alternately perform a read operation and a write operation every 1H. This is the same as during recording, but unlike during recording, the repetition frequency of the write clock pulse is, for example, 10 MHz.
In Z, the repetition frequency of the readout clock pulse is, for example, 8Ml-1z, so the time axis is expanded by the amount of time axis compression, that is, the time axis is expanded by 5/4)
The reproduced luminance signal is taken out from the RAM 8.9 alternately every day.

On the other hand, the AD converter 14. RAM15 and DA converter 16
The circuit section consisting of
After writing, a read operation is performed to obtain a line-sequential color difference signal whose time axis is returned to its original position. That is, RAM15
For example, write a digital signal of a reproduced time axis compressed color difference signal using a 10 MHz input/output clock pulse, and
The digital signal of the reproduction line sequential color difference signal whose time axis has been expanded five times and whose time axis has been restored by the Ml→Z readout clock pulse is read out. The read digital signal is converted into a reproduction line sequential color difference signal through the DA converter 16 and then supplied to the first input terminal of the encoder 34. In addition, the above-mentioned 1.
A 5 MHz discrimination burst signal is detected and provided to a second input terminal of encoder 34 .

The encoder 34 outputs a color difference signal (R-
After giving a predetermined DC level difference to each line (Y) and (B-Y), frequency modulation is performed to obtain a frequency modulated wave, and then only the horizontal synchronizing signal of the frequency modulated wave and the period before and after it are received. Transmission of the frequency modulated wave is interrupted to generate a carrier color signal which is a frequency modulated wave conforming to the SECAM system.

SECAM taken out from the output terminal of encoder 34
The reproduced carrier color signal that conforms to the SECAM system is supplied to the mixing circuit 35 shown in FIG. The reproduced color video signal is converted into a reproduced color video signal conforming to the following, and then outputted to the output terminal 36.

Note that it is also possible to record and reproduce line-sequential color difference signals while maintaining a DC level difference without providing a DC shift circuit inside each of the decoder 4 and encoder 34. In this case, the color reference level in the time-division multiplexed signal shown in FIG. 3(B) (the DC level of the achromatic color portion of the color difference signal within the backboard period) is the DC level difference.
t 11-1 fii, so the record +15 has A.
For the line-sequential color difference signal supplied to the D converter 14, only the color reference level of the transmission line of one predetermined color difference signal (RY) or (B-Y) is clamped, and the reproduction line is also clamped during reproduction. It is necessary to clamp only the color reference level of one of the color difference signal transmission lines of the sequential color difference signals.

However, since the discrimination information of the color difference signals (R-Y) and (F3-Y) is transmitted as the difference between the DC levels mentioned above, there is no need to override the transmission of the discrimination parse 1 to signal, and when performing DC level shift. In comparison, the circuit configuration is simple.

In a recording and reproducing apparatus that performs such a recording and reproducing apparatus, a control pulse generator 7 is provided with a clock pulse generator to which a horizontal synchronizing signal is supplied from a circuit 6 for synchronization during both recording and reproducing. It has a circuit. The present invention relates to this clock pulse generation circuit, and particularly to clock pulse generation during reproduction.

FIG. 4 shows a block diagram of an embodiment of the circuit of the present invention. In the figure, the reproduced horizontal synchronization signal from the synchronization separation circuit 6 is supplied to a phase comparator 40 in a first phase locked loop (PLL) 39 via an input terminal 38, where the output pulse of a counter 43 is The phase is compared with The phase error voltage extracted from the phase comparator 40 is applied to a voltage controlled oscillator (VCO) 42 through a loop filter 41 having low-pass filter characteristics with a cut-off frequency of, for example, 100 Hz, and variably controls its oscillation frequency.

The output oscillation center frequency of this VCO42 is 500kl-1
The frequency is selected to be about z, and after being frequency-divided by a counter 43 and converted into a horizontal scanning frequency, it is applied to the phase comparator 40. This phase comparator 40. Loop filter 41. V
The return loop consisting of CO42 and counter 43 is the first p
Since the cutoff frequency of the loop filter 41 is selected to be approximately 100) (z), the PLL 39 constituting the H39 suppresses the playback time axis fluctuation (jitter) of the playback horizontal synchronization signal that exists up to 3kl-1zPi[ Of which, 1'00
It has a response characteristic that follows reproduction time axis fluctuations of low frequencies of about 1-12, and can substantially eliminate noise in the reproduction horizontal synchronization signal.

Approximately 500 to 17 pulses extracted from the VCO 42 in the first PLL 39 and which follow the low playback time axis fluctuation of the playback horizontal synchronization signal are used as an example of a delay circuit (phase shift circuit). The voltage is applied to a monostable multivibrator (hereinafter referred to as "monomulti") 44. The delay amount of this monomulti 44 is controlled by the output signal of the loop filter 41 from the next extrusion. In other words, when the phase of the output pulse of the counter 43 lags behind the phase of the reproduced horizontal synchronizing signal, the first PLL 39 causes the output phase error voltage of the phase comparator 40 to become high, thereby increasing the output oscillation frequency of the VCO 42. On the other hand, when the phase of the output pulse of the counter 43 is ahead of the phase of the reproduced horizontal synchronizing signal, the phase error voltage becomes low and the output oscillation frequency of the VCO 42 is operated to be varied low, and the output pulse of the reproduced horizontal synchronizing signal Although the configuration is such that phase-synchronized pulses are output from the VCO 42, as mentioned above, the cutoff frequency of the loop filter 41 is low, so the delay time due to the loop filter 41 is large.
Tracking of the phase error is slow, and the phase difference between the two human input signals of the phase comparator 40 cannot be said to be accurate. For this reason,
In order to accurately compensate for the phase error in the phase comparator 40, the delay amount of the monomulti 44 is controlled by the output signal of the loop filter 41.

The output delayed pulse of the monomulti 44 is supplied to a phase comparator 46 constituting a second PLL 45, where a counter 5
After the phase is compared with the pulse from 0, the loop filter 4
7 to the VCO 48. The output oscillation center frequencies of the VCOs 4 and 8 are selected to be, for example, about 40 M l-1z, and are supplied to counters 49, 52, and 53, respectively. °The output pulse of counter 49 is the output pulse of counter 5
After being divided by 0 to approximately 500k) (Z), it is supplied to the phase comparator 46.A round feedback loop consisting of the phase comparator 46, loop filter 47°VCO 48, counters 49 and 50 is connected to the second P Approximately 40M+1 pulses are taken out from the VCO 48 and are phase synchronized with the pulses that are delayed by a period smaller than one horizontal scanning period by the monomulti 44.

The output pulse of the counter 49 is also output from the output terminal 51.
output as a clock pulse. On the other hand, counter 5
2. '53 is a counter with a different frequency division ratio, and the VCO
48 output pulses are frequency-divided and sent to output terminals 54 and 55, respectively, at the desired repetition frequency. Output a third clock pulse. The clock pulses taken out from the output terminals 51, 54, and 55 are used as read clock pulses and write clock pulses for the RAMs 8.9 and 15 described above, and are also used as control pulses for the AD converters 5 and 14. .9.15 and the [)A converters 11.16. In fact, a ludge gate is provided on the input side of the DA converter 11.16, and the ludge gate is connected to the output terminals 5j, 5.
4. ．． The latch operation is performed by the output clock pulse of 55. As a result, the time-domain compressed luminance signal and the time-domain compressed line-sequential color difference signal are each subjected to time-domain expansion at the same timing as the time-domain compression.

As described above, according to this embodiment, the second PLL 45 is controlled in a feedforward manner using the monomulti 44, so that the required repetition frequency can be maintained with almost no fluctuation in the playback time axis in the playback horizontal synchronization signal. Generates clock pulses
In addition, since the two PLLs 39 and 45 are used to generate pulses with the necessary repetition frequency in two stages, it is easy to design the PLLs 39 and 45 for stable operation.

According to this embodiment, by supplying the output pulse of the monomulti 44 to the counter 56 and resetting the counter 56 with the output pulse of the counter 43,
The counter 56 is configured to output a horizontal scanning frequency signal from which reproduction time axis fluctuations have been substantially removed to an output terminal 57. The output signal of this output terminal 57 is, for example, the first
The signal is output to the 1c mixing circuit 35 shown in the figure as a horizontal synchronizing signal during reproduction.

Application Example The circuit of the present invention is a circuit that can be applied when reproducing a time-division multiplexed signal using a time-plex method, but when applied to the recording/reproducing apparatus shown in FIG. 1, it can also be used during recording. Of course, other known circuits other than the monomulti 44' can also be used as the pulse delay circuit. Further, the second pLl-45 may be configured by cascading a plurality of stages of pH-.

Effects As described above, according to the present invention, the response characteristic of the first phase-locked loop to which the reproduced horizontal synchronizing signal is supplied is made to follow the reproduction time axis fluctuation of the low frequency of the reproduced horizontal synchronizing signal, The output signal is supplied to the second phase-locked loop through the delay circuit, so that the clock pulse that follows the low-frequency playback time axis variation can be passed to the second phase-locked loop without reacting to noise in the playback horizontal synchronization signal. It can be extracted from the phase-locked loop, and since the two phase-locked loops generate clock pulses with the required repetition frequency, the circuit configuration allows each phase-locked loop to operate stably. Since the clock pulse can be generated stably, even if the reproduced horizontal synchronization signal contains fluctuations in the reproduced time axis, the reproduced time axis compressed luminance signal and the reproduced time axis compressed line are sequential. This method has the advantage of being able to cover the time axis expansion of the color difference signals from the same timing position as when compressing the time axis, and preventing the occurrence of color shift.

[Brief explanation of the drawing]

FIG. 1 is a block system diagram showing an example of a recording/reproducing device previously proposed by the applicant to which the circuit of the present invention can be applied, FIGS. 2(A) to 3(F), and FIG. 3(A). (B) is a signal waveform diagram for explaining the operation of the block system shown in FIG. 1, and FIG. 4 is a block system diagram showing an embodiment of the circuit of the present invention. 1... Standard color video signal input terminal, 4... Decoder, 5, 14... AD converter, 6... Synchronization separation circuit, 7... Control pulse generator, 8,9゜15 ...Random access memory (RAM), 1
1,'16...DA converter, 12.38-...switch circuit, 17...discrimination berth]・Signal generation circuit, 2
2...[M transformer, 26...magnetic tape, 31...
- FM demodulator, 34...Enter, 35...Mixing circuit, 36...Reproduction standard color video signal output terminal, 38-...Reproduction horizontal synchronization signal input terminal, 39...No. 1 phase-locked loop (PLl,), 40
．． 46... Phase comparator, 41.47... Loop filter, 42° 48... Voltage controlled oscillator (VCO), 4
3.49°50', 52, 53.56... counter,
44... Multi-vibrator (mono-multi),
51.54.55...Return pulse output terminal, 57
...Horizontal synchronization signal output terminal.

Claims (1)

[Claims] Two types of time-axis compressed color difference signals are transmitted alternately every horizontal scanning period, and the - time-axis compressed color difference signals are time-division multiplexed together with the time-axis compressed luminance signal and the horizontal synchronization signal within one horizontal scanning period. A clock synchronized with the phase of the reproduced horizontal synchronization signal in the reproduced time division multiplexed signal obtained by demodulating the reproduced signal by reproducing the recording medium on which the time division multiplexed signal is modulated and recorded. Based on the pulses, the time axis compression in the reproduced time division multiplexed signal using memory is performed.
A color video signal reproducing device that expands a luminance signal and two types of time-axis color difference signals to their original time axes, and obtains a reproduced standard color video signal from the reproduced luminance signal and two types of color difference signals obtained thereby. a first phase-locked loop, which is a clock pulse generation circuit, to which the reproduced horizontal synchronizing signal is supplied and which has a response characteristic that follows low-frequency reproduction time axis fluctuations of the reproduced horizontal synchronizing signal; The delay amount is variably controlled by the output signal of the loop filter in the phase-locked loop, and the delay amount is variably controlled by the output signal of the loop filter in the phase-locked loop.
A delay circuit delays and outputs the output signal of the voltage controlled oscillator in the locked loop, and a second phase locked circuit receives the output signal of the delay circuit and generates and outputs an output pulse with a required repetition frequency. A clock pulse generation circuit for a color video signal reproducing device characterized by being configured with a loop.