JPS6359597B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In a so-called U-matic VTR, recording and reproduction are performed as shown in FIG. In the figure, a video signal supplied to an input terminal 1 is supplied to a luminance signal and chroma signal separation circuit 2, and the separated luminance signal is passed through an FM modulator 3 to a mixing circuit 4.
is supplied to Also, separated by separation circuit 2
A 3.58 MHz chroma signal is supplied to the frequency converter 5, and a 4.27 MHz converted signal from the oscillator 6 is supplied to form a chroma signal that has been low frequency converted to 688 kHz. This chroma signal is mixed with the above-mentioned luminance signal in a mixing circuit 4, and this mixed signal is supplied to a rotary head device 8 through a changeover switch 7 and recorded on a tape 9.

On the other hand, during reproduction, the signal from the rotary head device 8 is supplied to the high-pass filter 10 through the changeover switch 7, and the luminance signal is separated. This luminance signal is passed through the FM demodulator 11 to the mixing circuit 1.
2. Further, the signal from the changeover switch 7 is supplied to the low-pass filter 13, and the chroma signal is separated. This chroma signal is supplied to frequency converter 14. On the other hand, the reference frequency is 688kHz.
The signal from VCO15 and the signal from oscillator 16
The 3.58 MHz signal is supplied to the frequency converter 17 to form a 4.27 MHz converted signal. This converted signal is supplied to the frequency converter 14,
The chroma signal is high frequency converted to 3.58MHz. This chroma signal is supplied to the phase comparison circuit 18, and at the same time, a 3.58 MHz signal from the oscillator 16 is supplied to the comparison circuit 18, and this comparison output is supplied to the VCO 15 to perform APC. Furthermore converter 1
The chroma signal from 4 is mixed with the above-mentioned luminance signal in a mixing circuit 12, and this mixed signal is taken out at a terminal 19.

When attempting to incorporate such a reproduced signal into broadcasting standards, time axis correction is performed to remove jitter and the like in the reproduced signal. The time base correction device (TBC) for this purpose is configured as follows.

That is, in FIG. 1, a signal from a terminal 19 is supplied to a memory 21 through an AD conversion circuit 20. At the same time, the signal from the terminal 19 is supplied to the synchronization separation circuit 22 to separate horizontal and vertical synchronization signals, and this horizontal synchronization signal is supplied to the AFC circuit 23, which contains jitter equivalent to that of the reproduced signal, for example, color subtraction. A clock signal with a frequency four times that of the carrier wave is formed. This clock signal is used by the memory control circuit 2.
4. Further, the vertical synchronization signal from the synchronization separation circuit 22 is supplied to the control circuit 24, and the clock signal from the control circuit 24 is supplied to the conversion circuit 20 and the memory 21. The signal from the terminal 19 is then stored in the memory 21 during a predetermined period.

Furthermore, the signal from the memory 21 is transmitted to the DA conversion circuit 2.
5 and a clock signal with a frequency four times that of the color subcarrier from the reference oscillator 26 is supplied to the control signal 24, and this clock signal is supplied to the memory 2.
1 and the conversion circuit 25, and the read signal is taken out to the output terminal 27.

However, in the above-mentioned device, the chroma signal in the reproduced signal taken out to the terminal 19 is
The phase is controlled by the signal from , and jitter is removed.

Therefore, if such a signal is supplied to the TBC, the horizontal synchronization signal in the luminance signal is detected, and time correction is performed to eliminate jitter in the luminance signal, jitter in the opposite direction will be added to the chroma signal. I'm getting used to it.

Furthermore, when performing variable-speed playback such as slow playback or double-speed playback in the above-mentioned VTR, the same field is played repeatedly or fields are played intermittently, resulting in a loss of continuity in the playback signal.

In other words, for example, in an NTSC video signal, the signal is shifted by 1/2 horizontal period in the second field with respect to an arbitrary first field.
In the third field, the phase of the chroma signal is inverted, and in the fourth field, the chroma signal is shifted by 1/2 horizontal period and the phase of the chroma signal is inverted.
These first to fourth fields are repeated in order.

Therefore, for example, when performing still reproduction, the above-mentioned first to fourth fields are formed from a single field. That is, in the first field, the signal is extracted as is, in the second field, the signal is delayed by 1/2 horizontal period and extracted, in the third field, the phase of the chroma signal in the signal is inverted and extracted, and in the fourth field, it is extracted by 1/2 The signal delayed by the horizontal period is further extracted by inverting the phase of the chroma signal in the signal.

In this case, the delay of 1/2 horizontal period can be performed by the above-mentioned TBC. However, in order to invert the phase of the chroma signal, the luminance signal and chroma signal must be separated again, and if such separation is repeated, there is a risk that the signal will be significantly degraded.

In view of these points, the present invention solves these problems with a simple configuration.

That is, the present invention separates a chroma signal in a reproduced video signal in which the chroma signal has been low-frequency converted, converts this chroma signal to a high frequency using a predetermined conversion signal, and converts this high-frequency converted chroma signal. When mixing the chroma signal with the reproduced video signal from which the chroma signal has been removed and extracting this mixed signal by time-base correction, the jitter in the mixed signal is detected, and the converted signal is corrected according to this jitter. In addition to giving equal jitter to the chroma signal, the continuity of the mixed signal is detected, and the phase of the converted signal is inverted based on this detection signal.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2, parts corresponding to those in FIG. 1 are given the same reference numerals.

In FIG. 2, a color subcarrier containing the same jitter as the reproduced signal is extracted from the AFC circuit 23, and this signal is supplied to the phase correction circuit 28. Further, the control circuit 24 detects the continuity of the chroma signal, and supplies a signal indicating that the chroma signal has become discontinuous to the correction circuit 28. When this signal is supplied, the phase of the color subcarrier is inverted. This color subcarrier is taken out to terminal 29.

In the VTR, instead of the oscillator 16,
A signal from terminal 29 is supplied to converter 17 and comparison circuit 18 through changeover switch 30.

Therefore, in this device, the converter 17 and comparator circuit 18 of the VTR are supplied with a color subcarrier having a jitter equal to that of the reproduced signal, and the converter 17 takes out a converted signal having a jitter equal to that of the reproduced signal. As a result of high-frequency conversion, a chroma signal having jitter equivalent to that of the luminance signal is extracted from the converter 14.

Furthermore, when the phase of the chroma signal in the reproduced signal becomes discontinuous, the phase of the color subcarrier supplied to the converter 17 and the comparison circuit 18 is inverted, and thereby the phase of the converted signal taken out from the converter 17 is inverted. Ru. As a result, the phase of the high frequency converted chroma signal is inverted, and the phase of the chroma signal in the reproduced signal is made continuous.

In this way, the reproduced signal from the VTR is taken out through the TBC, but according to the present invention, the converted signal when performing high frequency conversion is given jitter and phase inversion is performed as necessary. , it is possible to always perform good time axis correction, and also maintain continuity of chroma signals.

Furthermore, since there is no need to separate the luminance signal and the cross signal, signal deterioration does not occur and the configuration is extremely simple.

Note that VTRs have already been announced that are provided with a terminal corresponding to the terminal 29 in order to use external synchronization and the like. The present invention can be easily applied to such a VTR, and can also be applied to a device that integrates a VTR and a TBC.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a conventional device, and FIG. 2 is a system diagram of an example of the present invention. 14 and 17 are frequency converters, 15 is a VCO,
18 is a phase comparison circuit, 22 is a synchronous separation circuit, 23
is an AFC circuit, and 28 is a phase correction circuit.

Claims (1)

[Scope of Claims] 1. A video signal in which a chroma signal is frequency-converted to a lower frequency band of a luminance signal is reproduced, a jitter component included in the chroma signal is detected, and a converted signal containing this jitter component is used to reproduce the chroma signal. In a playback device that performs high-frequency conversion of a signal, mixes the high-frequency converted chroma signal and a luminance signal, and performs time axis correction on this mixed signal, the time included in the luminance signal in the mixed signal is a first means for detecting an axis variation; a second means for detecting continuity of color subcarriers in the mixed signal; and adding the time axis variation from the first means to the converted signal; and means for controlling the phase of the converted signal using the continuity detection signal from the second means.