JPH0523119B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a color television signal recording system, and more particularly to a color signal recording system that is compatible with the conventional color under system.

[Prior art]

An example of the color under system, which is a conventional color television signal recording system, is the 8mm video standard. The problem with the color under method is that it is difficult to obtain a sufficient S/N ratio for the color signal and that it is difficult to secure a sufficient bandwidth for the luminance signal.

Hereinafter, the problems of the prior art will be explained in detail with reference to the drawings. FIG. 1 is a block diagram showing a recording circuit of an 8 mm video standard video tape recorder, and FIG. 2 is a diagram showing the spectrum of the recording signal according to FIG. In FIG. 1, 24 is a video signal input terminal, 16 is an AGC circuit for keeping the amplitude constant,
17 is an LPF that suppresses the chroma signal and extracts only the luminance signal, and 18 is a synchronization separation circuit that outputs both horizontal and vertical synchronization signals. 19 is a vertical synchronization signal extraction circuit, 20 is a monostable multivibrator for frequency division into 1/2, 7 is a phase comparator, 8 is a motor driver, 9 is a drum motor that rotates the video head, 2 and 3 are The rotating video head 5 is a drum pulse pickup head for detecting the rotational phase of the video head.
5, 6, 7, 8, and 9 constitute a phase-locked loop, and the video head rotates in phase synchronization with the frame frequency (1/2 of the vertical synchronization frequency) of the input video signal. 10 is a capstan motor, 11 is a head for detecting the rotational phase of the capstan, 12 is a pulse amplifier, 13 is a phase comparator, 14 is a reference frequency generation circuit consisting of a crystal oscillator and a frequency divider, 10, 11, 12, 13, 14, and 15 also constitute a phase synchronization circuit, and have the function of running the tape 1 at a constant speed. 21 is an emphasis circuit, 22 is a frequency modulation circuit, and 23 is an HPF, the outputs of which provide signals with spectra shown at 38, 39, and 40 in FIG. 38 is a carrier of a signal obtained by frequency modulating a luminance signal (hereinafter referred to as Y _FM ), 39 is a lower side band wave of Y _FM , and 40 is an upper side band wave of Y _FM . 25 is BPF for extracting chroma signal,
26 is a low-frequency conversion circuit, 27 is a color killer circuit that shuts off the circuit when there is no chroma burst, and 28 is an LPF for suppressing unnecessary signals, and a signal having the spectrum shown at 42 in FIG. 2 is obtained at its output. 42 indicates a low frequency converted chroma signal (hereinafter referred to as C _L ). 2
Reference numeral 9 designates an input terminal for audio signals, 30 represents an audio signal processing circuit, 31 represents a frequency modulation circuit, and 32 represents a BPF for suppressing unnecessary signals. At its output, a signal having a spectrum shown at 41 in FIG. 2 is obtained. 41 is a signal obtained by frequency modulating an audio signal (hereinafter referred to as _AFM ). 33 is a phase comparator, 34 is a 1/378 frequency divider, 3
5 is a VCO of _378fH ( _fH : horizontal synchronization frequency), 36 is a frequency divider, and 33, 34, and 35 constitute a phase synchronization circuit. A signal having a frequency of 378f _H that is phase synchronized with the horizontal synchronization signal which is the output signal of the synchronization separation circuit 18 is obtained as the output of the VCO 35. The frequency division ratio of the frequency divider 36 is switched to 1/58, 1/50, 1/36, and 1/40 for each field of the input video signal, and the outputs are approximately 6.5f _H , 7.5f _H , and 10.5f. A signal with a spectrum shown at 43 _{in FIG. 2 having a frequency of 9.5f H is} obtained. 43
is a 4-frequency pilot signal for tracking servo. Reference numeral 37 denotes a recording amplifier, which outputs signals 38, 39, 40, 41, 42, 4 shown in FIG.
Write a signal with a spectrum of 3.

The problems with the conventional method are (1) Y _FM bandwidth is limited because A _FM and _CL are frequency-multiplexed below Y _FM , and (2) _CL is recorded with a bias bias of Y _FM . (3) Since C _L has a subcarrier, it is susceptible to fluctuations in the time axis, making it difficult to ensure image quality.

[Purpose of the invention]

The purpose of the invention is to eliminate the drawbacks of the prior art and _to
An object of the present invention is to provide a new recording circuit for video signals, which makes it easy to secure a bandwidth and is not affected by amplitude modulation noise or time axis fluctuations.

Another object of the present invention is to provide a recording circuit capable of recording both the conventional color under method and the new method.

[Summary of the invention]

In the present invention, the luminance signal and the horizontal and vertical synchronization signals are time-compressed at the same rate, the chroma signal is time-compressed at a greater rate, and the luminance signal and the chroma signal are recorded by time division multiplexing.

In a circuit that combines the conventional color under method and the new method described above, depending on the presence or absence of the chroma burst signal, a band limiting filter (LPF and
HPF) to a wide band for the new method and a narrow band for the color under method.

The time compression ratio of the synchronization signal is set within a range that allows the conventional horizontal synchronization signal extraction circuit and vertical synchronization signal extraction circuit to operate sufficiently, and the rotation phase control circuit of the rotating video head and the pilot signal generation circuit for the tracking servo are both combined. The same shall apply.

With the above configuration, in the color under method, recording of both methods is possible by simply adding a filter switching circuit for the luminance signal circuit and a time division multiplex signal generation circuit. Some of the conventional color under type video tape recorders have the above-mentioned filter switching function called B/W mode, and in this case, a time division multiplex signal generation circuit can be connected with an adapter.

For those with relatively wide luminance signal bands, such as the 8mm video standard and U-matic, it is possible to record in a new format by connecting a time division multiplex signal generation circuit with an adapter, even without the band switching function described above.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings. Fig. 3 is a block diagram showing an embodiment of the video tape recorder of the present invention which is capable of both time division multiplexing and color under recording. FIG. 5 is a block diagram showing one embodiment of the invention, FIG. 5 is a waveform diagram showing an example of a time division multiplexed signal used in the invention, and FIG.
The figure is a diagram showing a recording signal spectrum of a time division multiplexing system.

The differences between FIG. 3 and FIG. 1 will be explained. The input terminal 24 receives not only normal composite video signals, but also
A time division multiplexed signal shown at 58 in FIG. 5 is also input. The switches 45 and 46 are connected to the black circle side during color under recording, and are connected to the white circle side during time division multiplex recording. Color Killer 27, A _FM
The killer 47 transmits a signal during color under recording and shuts off the time division multiplex recording circuit.
The output signal of the pilot signal generator 36 is the same pilot signal since both types have horizontal synchronization signals of the same frequency. Therefore, the output signal spectrum of the recording amplifier 37 is as shown in FIG. In FIG. 6, 60 is a carrier of a frequency-modulated time division multiplexed signal, 61 is a lower sideband wave, and 62
is the upper sideband wave. The upper and lower sidebands are hardly subject to any band limitations and are much wider than the sidebands of the color under system. For both types, the emphasis circuit 21 and frequency modulation circuit 22 are the same, so the carrier frequencies are also almost the same.
Reproduction is possible using the same reproduction circuit.

Although the vertical synchronization signal is not explained in FIG. 5, the vertical synchronization signal of the time division multiplexed signal has the same frequency as that of the color under, and the pulse width is time-compressed. If the time compression ratio is 2/3 or more, the vertical synchronization separation circuit 19 will not malfunction, and therefore both drum motors 9 will rotate at the same rate.

In Figure 3, the burst detection circuit 4 performs both types of discrimination.
4 with or without chroma burst.
Reference numeral 59 in FIG. 5 is a burst signal for discriminating the RY and BY signals, which has a different frequency from the chroma burst.

In FIG. 4, 50 is an input terminal for a composite video signal, 49 is a time division multiplex signal generation circuit, and 51 is an output terminal for a time division multiplex signal, from which the waveform 58 in FIG. 5 is output. FIG. 7 is a block diagram showing one embodiment of the time division multiplexed signal generating circuit 49 of FIG. 4.

In FIG. 7, 65 is an AGC circuit for keeping the amplitude within a constant value, and 66 is an LPF for suppressing chroma subcarriers, whose output has the waveform shown in FIG. 52. 63 in FIG. 5 is a horizontal synchronizing signal having a regular pulse width. 67 is an AD converter, 68 is a memory, 69 is a DA converter, and the fifth
A waveform shown at 55 in the figure is obtained. 64 in FIG. 5 is a time-compressed horizontal synchronizing signal. 70 is a BPF for extracting chroma signals, 71 is a color difference signal demodulation circuit,
72 is an RY signal output terminal, 73 is a BY signal output terminal, and the waveforms 53 and 54 in FIG. 5 are obtained.
74 is a switch for converting color difference signals into line-sequential signals, 75 is an AD converter, 76 is a memory, and 77 is a switch for converting color difference signals into line-sequential signals.
It is a DA converter, and its output is
Obtain the waveform of 78 is a phase comparator, 79 is a VCO,
80 is a 1/2 frequency divider, 81 is a 1/4 frequency divider, 82 is a phase comparator, 83 is a VCO, 84 is a 1/5 frequency divider, 85 is a 1/3 frequency divider, 86 is a waveform synthesizer It is a circuit.

In FIG. 7, the chroma subcarrier (455/2f _H in the case of NTSC) is taken out from the color difference signal demodulation circuit 71 and applied to the phase comparator 78, and the VCO
The output of 79 will be 455f _H. Therefore memory 6
The write clock of No. 8 becomes _455fH , the readout clock becomes 455×5/4= _568.75fH , and a signal whose time is compressed by 4/5 times can be obtained at the output of the DA converter 69.

Similarly, the write clock of the memory 76 is 455/4f _H = 113.75f _H , the read clock is 455/4 x 5f _H = 568.75f _H , and the output of the DA converter 77 has time compressed to 1/5 times. I can get a signal. 1/3
The output signal of the frequency divider 85 is a burst signal (59 in FIG. 5) for discriminating the R-Y and B-Y signals.
In the figure, a burst signal of 455/3f _H =1512/3f _H is added only during the period of the RY signal.

As can be seen from FIG. 6, the bandwidth of the time division multiplexed signal is secured at about 5 MHz, and even if the above-mentioned 4/5 time compression is taken into account, the luminance signal band can be secured at about 4 MHz. For chroma signals, the time compression ratio is 1/
5, and approximately 1 MHz of bandwidth is secured. In the present invention, since the chroma signal does not have a subcarrier and is frequency modulated and recorded on the tape, it is completely unaffected by the above-mentioned amplitude modulation noise and time axis fluctuation, and good chroma image quality can be obtained.

A feature of the time division multiplexed signal of the present invention is that the synchronization signal and the luminance signal have the same time compression ratio with respect to the original signal. The methods that have been proposed so far replace the horizontal synchronization signal with a special one, which may cause the pilot signal generation circuit of conventional video tape recorders to malfunction, or cause image shake because the horizontal synchronization signal is replaced during playback. However, it has not been put into practical use because it is prone to problems such as incorrect pedestal settings. In the present invention, during reproduction, the synchronization signal and the luminance signal are simply time-expanded at the same rate, and there is no need to replace the synchronization, so the above problem does not occur.

〔Effect of the invention〕

According to the present invention, it is possible to widen the bandwidth of a luminance signal, and to obtain good chroma image quality that is almost unaffected by amplitude modulation noise and time axis fluctuations.

Furthermore, it becomes possible to record time division multiplexed signals simply by connecting an adapter to a conventional color under system video tape recorder.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a recording circuit of a conventional color under type video tape recorder, FIG. 2 is a diagram showing a spectrum of a conventional recording signal, and FIG. 3 is an implementation of the recording circuit of a video tape recorder according to the present invention. A block diagram showing an example; FIG. 4 is a block diagram showing the principle of the time division multiplexing video tape recorder of the present invention; FIG. 5 is a diagram showing waveforms of each part of FIG. 7;
FIG. 6 is a diagram showing a spectrum of an embodiment of a recording signal of a time division multiplexing video tape recorder of the present invention, and FIG. 7 is a block diagram showing an embodiment of a time division multiplexing signal generation circuit of the present invention. . Explanation of symbols, 49... Time division multiplexed signal generation circuit, 50... Composite video signal input terminal, 18...
Synchronous separation circuit, 36...Pilot signal generation circuit, 1...Video tape, 37...Recording amplifier.

Claims (1)

[Claims] 1. A color video signal of a first method in which a chroma signal including a burst signal and a luminance signal are frequency-multiplexed in a predetermined frequency band, and a chroma signal and a luminance signal in the predetermined frequency band are an input terminal to which a division multiplexed color video signal of a second method is supplied; and a bandpass filter that frequency-separates a chroma signal and a luminance signal from the first method color video signal supplied to the input terminal. and a low-pass filter; a transmission means that is provided in parallel with the low-pass filter and outputs the color video signal of the second method supplied to the input terminal while maintaining its band; and an output signal of the band-pass filter. determining means for determining whether the color video signal supplied to the input terminal is of a first or second method based on the presence or absence of a burst signal; selection means for selecting an output signal of the low-pass filter when a color video signal of a second method is supplied, and selecting an output signal of the transmission means when a color video signal of a second method is supplied; By the output signal output from
FM modulation means for outputting an FM-modulated FM signal; and low-frequency conversion means for frequency-converting the output signal of the bandpass filter to a lower frequency band, and the first method is determined according to the output of the discrimination means. When a color video signal is supplied, the low frequency conversion signal from the low frequency conversion means is allowed to be output, and when a color video signal of the second method is supplied, the low frequency conversion signal is output. a recording amplifier connected to the output of the FM modulation means and the output of the chroma signal processing means, and a magnetic head connected to the output of the recording amplifier. A color video signal recording device characterized by: