JPS6120483A - Video signal reproducing device - Google Patents

Abstract

PURPOSE:To improve efficiency of recording of a recording medium and remove disturbing signals by correcting time base error included in signals frequency converted to low band and recorded and reproduced and signals frequency modulated and recorded reproduced by making a time base reference signal included in reproduced video signals a time base reference. CONSTITUTION:As a read address generating circuit 10 is controlled by a reference horizontal synchronizing signal that becomes standard of time bas and reference clock having frequency of 910 fH, time base error caused by a tape head system etc. is removed, and supplied to DA convertors 6, 14. Further, the reference clock is also supplied to DA convertors 6, 14. Thus, demodulated signals of band from zero to above 3MHz from which time base fluctuation is removed are obtained in the output terminal of the DA convertor 6, and signals transmitted in low band conversion transmission zone from which time base fluctuation is removed are obtained in the output terminal of the DA convertor 14. Carrier for balanced modulation for returning signals transmitted in low band conversion transmission zone to original band is supplied to a terminal 21.

Description

Detailed Description of the Invention: The video signal is recorded in the field of industrial use, and the low frequency component of the video signal is frequency-modulated to a higher frequency portion than the signal frequency-converted to the low frequency range and recorded on the recording medium. The present invention relates to an apparatus for reproducing the video signal from the recording medium.

Conventional configurations and their problems Conventionally, in home video tape recorders, etc., a signal is obtained by frequency converting the high frequency night portion of a video signal including a carrier color signal to a low frequency band, and a signal in which the low frequency component of the video signal is converted to a low frequency component is converted into a low frequency component. The frequency-converted signal is added to the frequency-modulated signal in the higher frequency range, and the resultant signal is recorded on a video tape or the like. When playing,
In the process of converting the frequency of the signal containing the carrier color signal converted to the low frequency band to the original high frequency band, the time axis variation (phase variation) included in the carrier color signal is removed, and the frequency modulated signal is demodulated. The reproduced video signal was added to the signal and displayed on the monitor TV receiver. This is because in the recording and playback system of a home video tape recorder, a certain amount of time axis fluctuation occurs, and this time axis fluctuation causes the phase of the carrier color signal to fluctuate significantly, so it is necessary to remove this phase fluctuation. It's for a reason.

In addition, in the low-frequency component of the video signal, that is, the luminance signal, the time axis fluctuation that occurs in a home video tape recorder is
Since its frequency component is low, it is removed by the AFC circuit included in the monitor television receiver. For this reason, there is no particular need to correct (remove) the time axis variation included in the luminance signal, and a circuit for correcting the time axis variation for the luminance signal has not been provided.

Therefore, among the signals including the carrier color signal converted to the low frequency signal, the high frequency component of the luminance signal is not used effectively.
The utilization efficiency of the recording medium in the home video tape recorder was poor.

Furthermore, the time axis of the low-frequency component of the luminance signal transmitted by the frequency modulation system and the high-frequency component of the luminance signal transmitted by the low-frequency conversion system is different due to the presence or absence of time axis correction. Therefore, there is a problem in that the high-frequency component of the luminance signal acts as a kind of interference signal on the image displayed on the monitor television receiver.

Purpose of the Invention The present invention solves the above-mentioned problems and improves the recording efficiency (linear recording density) of a recording medium by also using the high-frequency component of the luminance signal transmitted in the low-frequency conversion system as a reproduced video signal. The purpose of this system is to eliminate the high-frequency components of the luminance signal from acting as a kind of interference signal by using the high-frequency components of the luminance signals transmitted in the low-frequency conversion system as playback video signals. It is.

Structure of the Invention In reproducing the video signal from the recording medium in which the low frequency component of the video signal is frequency-modulated to a higher frequency portion than the signal frequency-converted to the low frequency and recorded on the recording medium, the video signal is reproduced. Using the time axis reference signal included in the video signal as a time axis reference, the time axis error included in the signal that has been frequency-converted to the low frequency range and recorded and reproduced is corrected, and the time axis error included in the signal that has been frequency-modulated and recorded and reproduced is corrected. It is configured to correct the included time axis error.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a frequency allocation run of a recording signal in a conventional example (for example, VH3 standard). In FIG. 1, the low frequency conversion transmission band transmits only the carrier color signal, and the FM transmission band transmits only the luminance signal. In the FM transmission band, a signal of approximately 2.51 times (approximately 200 TV lines in horizontal resolution) is transmitted at the black level, and approximately 2.51 times the signal at the dark level is transmitted.
．． 91tk (2SoTV lines) signals are transmitted.

On the other hand, FIG. 2 is a diagram showing the frequency allocation of the recording signal in one embodiment of the present invention.
4 OTV or more) signals are transmitted. As described later, in the low-frequency conversion system, the high-frequency components of the luminance signal and the carrier color signal are
i ~ about 4M, equivalent to 5oTv, is transmitted. As a result, more than 4 parts (Fig. 3 shows the entire circuit block diagram in one embodiment of the present invention. Fig. 3 shows the playback circuit section in a video tape recorder, including a rotary cylinder, a video tape 1, etc.) The mechanism is omitted as it is unnecessary for the explanation.The signal reproduced by the video head 1 is passed through a high-pass filter 2 and a low-pass filter 11.
Accordingly, the signal is separated into a frequency-modulated luminance signal included in the FM transmission band in FIG. 2 and a signal included in the low-frequency conversion transmission band. The output signal of the high-pass filter 2 is demodulated by a frequency demodulation circuit, and a demodulated signal (mainly a luminance signal) with a band from zero to three or more is obtained. This demodulated signal is supplied to an AD converter (analog-to-digital converter) 4 and a horizontal synchronizing signal separation circuit 7. The AD converter 4 is connected to a memory circuit 6, and the memory circuit 5 is connected to a DA converter (digital-to-analog converter) 6.

On the other hand, the horizontal synchronization signal separation circuit 7 separates the horizontal synchronization signal (described by H, two frequencies are described by fH) included in the demodulated signal, and supplies it to a PLL circuit (phase locked loop) 8. The PLL circuit 8 includes, for example, a phase comparator 25 and a low-pass filter 26, as shown in FIG. Consisting of a voltage controlled oscillator 27 and a frequency divider 9,
When the dividing ratio of the divider is set to □, a signal having a frequency of 910 fH is obtained at the output terminal of the PLL circuit 8. The horizontal synchronization signal and the output signal of the PLL circuit 8 are input to a write address generation circuit 9. The address of the write address generation circuit 9 is reset to zero by the horizontal synchronization signal, and thereafter the write address of the memory circuit @6 is set by counting the output signal of the PLL circuit 8. Similarly, write address generation circuit 9F
i. The write address of the memory circuit 13, which will be described later, is also set. On the other hand, the signal included in the low-pass conversion transmission band (the carrier color signal and the luminance signal component included in the carrier color signal band, that is, the high-frequency component of the luminance signal) converted into F waves by the low-pass filter 11 is The signal is supplied to the converter 12, converted into a digital signal, and supplied to the memory circuit 13. Further, clocks for AD converter 4 and AD converter 12 are provided from PLL circuit 8. The respective signals written to the memory circuits 5 and 13 in this manner are outputted from the memory circuits 6 and 13 according to the read address outputted by the read address generation circuit 1o. Here, the read address generation circuit 1o uses a reference horizontal synchronization signal (supplied to the input terminal 19, hereinafter referred to as reference H) serving as a time axis reference and a frequency of 91 OfH.
Since the reference clock (supplied to the input terminal 2o) is controlled by the reference clock (supplied to the input terminal 2o), time axis errors received by the tape head system (not shown) are removed, and the respective DA converters (digital-to-analog converters) 6. 14.

A reference clock (supplied to input terminal 20) is also supplied to the DA converter 6.14. This results in
At the output terminal of the DA converter 6, a demodulated signal (mainly a luminance signal) with a band of 0 to 3 or more from which time-axis fluctuations have been removed is obtained, and at the output terminal of the AD converter 14, a demodulated signal (mainly a luminance signal) with time-axis fluctuations removed is obtained. A signal transmitted in the low frequency conversion transmission band can be obtained. A balanced modulation carrier for returning the signal transmitted in the low frequency conversion transmission band to the original band is supplied to the terminal 21. The signal returned to its original band by the balanced modulator 16 passes through the bandpass filter 16 (
The pass center frequency is set to the color subcarrier frequency), and then added to the output signal of the AD converter 6 by the adder 17 and output to the output terminal 18.

That is, the signal output to the output terminal 18 mainly consists of a demodulated signal from zero to 3- or more consisting of a luminance signal, a carrier color signal, and a luminance signal component included in the carrier color signal band (luminance signal component of 3~4&Ik). Therefore, a signal in the band from zero to 4&lk (320 TV lines) and a carrier color signal are obtained as the luminance signal.

Note that the circuit block consisting of the AD converter 4, memory circuit 5, DART converter 6, horizontal synchronization signal separation circuit 7, PLL circuit 8, write address generation circuit 9, and read address generation circuit 1o is a so-called time base collector (time axis correction It is well known as a circuit) 29, but other configurations of the time base collector may also be used.

Further, the memory circuits 5 and 13 usually need to have a storage capacity sufficient to store data for a period of 3H or more.

Another embodiment is shown in FIG. The configuration shown in FIG. 5 differs from the configuration shown in FIG. 3 in that the output signal of the horizontal synchronizing signal separation circuit 7 is newly supplied to the PLL circuit 22. The PLL circuit 22 has a PLL circuit 5@a shown in FIG.
However, the passband of the low-pass filter 26 is extremely narrower than that of the PLL circuit 8, and the voltage-controlled oscillator 27 uses a crystal resonator. As a result, the responsiveness of the PLL circuit 22 is extremely slower than that of the PLL circuit 8, and has a characteristic of only following jitter components of a value equal to or less than several 1. From the PLL circuit 22, the frequency is 91 O.
A signal substituted for the fH reference clock signal is output from the voltage controlled oscillator 27, and a signal substituted for the reference H signal is outputted from the divider 28. This controls the time base collector 29. In the configuration shown in FIG. 6, time axis fluctuations are not completely removed (jitter components below the numerical ratio described above remain). However, since the monitor television receiver (not shown) connected to the output terminal 18 sufficiently responds to time axis errors of less than the above-mentioned numerical ratio, this does not pose a problem in actual use. On the other hand, since the signal substituted for the reference H signal and the signal substituted for the reference clock respond to jitter components of a numerical ratio or less, 2H is sufficient for the storage capacity of the memory circuits 6 and 13, and the circuit scale is becomes smaller.

As yet another embodiment, the configuration shown in FIG. 6 may be used. The difference between the configuration in FIG. 6 and the configuration in FIG. 3 is that the horizontal synchronizing signal separation circuit 7 directly performs KPLL,
This is the point where it is connected to.

The burst gate circuit includes the low-pass filter 1.
1 output signal is supplied, from which the low frequency converted color burst signal is extracted. Typically, the low-pass converted color burst signal is about 1.6 wavelengths. The zero-crossing point of this color burst signal is detected by the zero-crossing detection circuit 24, and is used as a substitute for the output signal of the horizontal synchronizing signal separation circuit 7 shown in FIG. 3 to control the time base collector 29. As a result, more accurate time axis correction can generally be expected than with the configuration shown in FIG.

Furthermore, similar to the configuration shown in FIG. 5, a PLL 22 may be provided to provide a similar configuration.

Further, as another configuration of the time base collector 29, a configuration such as a feedforward control type time base collector disclosed in the Technical Report of the Television Engineering Society (TEBS 83-1) may be used.

Effects of the Invention As described above, the video signal reproducing device of the present invention removes (corrects) the time axis error of both the signal transmitted in the FM transmission band and the signal transmitted in the low frequency conversion transmission band. After that,
Since the original video signal is restored by addition, in addition to the FM transmission band, the low frequency conversion transmission band is also used as a transmission path for the luminance signal, which improves the recording efficiency of the recording medium.
Linear recording density is effectively improved. Expressed in another way, the horizontal resolution is improved by about aoTV lines.

Furthermore, since the high-frequency component of the luminance signal transmitted in the low-frequency conversion transmission band is also used as a reproduced video signal, the high-frequency component of the luminance signal is removed from acting as a kind of interference signal.

Furthermore, by correcting only the time axis error components other than the low-frequency time axis error components corrected by the monitor television receiver, the above effects can be achieved with a small memory capacity. It will be done.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing frequency allocation of recording signals in a conventional video signal processing device, FIG. 2 is a diagram showing frequency allocation of recording signals used in an embodiment of the present invention,
FIG. 3 is a circuit block diagram of a main part of a video signal reproducing device according to an embodiment of the present invention, and FIG. 4 is a detailed circuit block diagram of some circuits in the main part block diagram shown in FIG. 3 or FIG. 6. , FIG. 6 is a block diagram of main parts of another embodiment.
The figure is a block diagram of main parts of yet another embodiment. 2... High-pass filter, 3... Frequency demodulation circuit, 4... AD converter, 6...
...Memory circuit, 6...DA converter,
γ...Horizontal synchronization signal separation circuit, 8...
PLL circuit, 9...Write address generation circuit, 10...Read address generation circuit, 11.
...Low pass filter, 12...AD
Co/verter, 13...Memory circuit, 14...
...DA converter, 1 end...Adder, 22
... PLL circuit, 23 ... Gate pulse generation circuit, 24 ... Zero cross detection circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 4

Claims (5)

[Claims] (1) From a recording medium in which the high-frequency component of a video signal is frequency-converted to a low-frequency range, and the low-frequency component of the video signal is frequency-modulated to a higher frequency part than the signal frequency-converted to the low frequency range and recorded. a reproduction means for reproducing the signal; a means for correcting a time-axis error contained in the signal frequency-converted to the low frequency band and recorded and reproduced, using the time-axis reference signal included in the reproduced video signal as a time-axis reference; and a video signal reproducing device comprising: means for correcting a time axis error included in a frequency-modulated signal recorded and reproduced. (2) The video signal reproducing device according to claim 1, wherein a horizontal synchronization signal included in the video signal is used as the time axis reference signal. (3) The video signal reproducing device according to claim 1, wherein a color burst signal included in the video signal is used as the time axis reference signal. (4) The video signal reproducing device according to claim 1, wherein a signal in a frequency band including a carrier color signal is used as the high frequency component of the video signal. (5) In correcting the time axis error included in the signal recorded and reproduced after frequency conversion to a low frequency band and the time axis error included in the signal recorded and reproduced after frequency modulation,
2. The video signal reproducing apparatus according to claim 1, wherein among the respective time axis error components, only components other than the low frequency components corrected by a monitor television receiver are corrected.