JPS6318915B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording and reproducing device for color video signals, and in particular to a small and lightweight recording and reproducing device that achieves high-quality reproduced images suitable for news reporting for broadcasting, etc. This provides a device with significantly less deterioration.

Conventionally, the mainstream of color video signal magnetic recording and reproducing devices (hereinafter referred to as VTRs) is of the helical scan type, in which a rotating head forms a video track diagonally on a tape. In particular, home VTRs are compact and high-density recording, sacrificing image quality to a certain extent compared to those used for broadcasting, but at the expense of significantly reducing tape consumption. For example, in a VHS system VTR, color video signals are recorded diagonally onto a 1/2 inch (12.65 mm) wide tape using two video heads placed on a rotating cylinder with a diameter of 62 mm so that they have a rotation angle of 180 degrees from each other. has been done. In addition, in the field of broadcasting VTRs, 2" VTRs and 1" VTRs have traditionally been used as news gathering (ENG) portable VTRs, but the devices are large and heavy, so there is a strong desire for smaller and lighter VTRs.
3/4-inch U-standard VTRs, which were developed for industrial use, have recently come into widespread use for news reporting. This 3/4 inch U standard VTR has a cylinder diameter of 110
mm, the tape width is 3/4 inch (18.98mm), so
There are limits to miniaturization, and the recording method for video signals has changed from color video signals to luminance signals (approximately 3M).
Hz band) and color signals (approximately ±500KHz band),
The separated luminance signal is frequency modulated on the high frequency side, its low frequency is removed, and the chrominance signal is superimposed with a signal converted to a low frequency and recorded as a spectrum as shown in Figure 1. In order to use the method of
The luminance signal and chrominance signal bands are limited, and the normally reproduced luminance signal band is about -6 dB at 3MHz, and the chrominance signal band is about -6 dB at a point 500 KHz away from the subcarrier frequency. Furthermore, with this recording method, the signal is recorded as information with amplitude and phase, so VTR
Due to the influence of time axis fluctuations, there are problems such as uneven hue and saturation on color monitors, and the image quality is not sufficient for broadcasting. Furthermore, in the ENG system, dubbing is performed several times as shown in FIG. That is, in Figure 2, 50 is a color camera and a portable VTR.
are shown integrated. This portable VTR
A news interview was conducted at 50, and the tape 51 of the interview was played back on the studio VTR 1 at 52, and the playback signal was transmitted to the studio 53 for only the necessary period.
Recorded on VTR2. Dubbing is performed by so-called electronic editing. Although not shown in FIG. 2, after such a method is performed several times, the time axis correction device 54 removes the time axis fluctuation, and
The apparatus is configured to obtain a color video signal of a broadcast station. As a result, as mentioned above, the dubbing image quality of 3/4-inch U standard VTRs, which have many band limitations, has low resolution and blurry image quality, color blurring due to the narrow color signal band, and even hue unevenness. The disadvantage was that the color saturation was uneven.

In view of the above points, the present invention provides a method for obtaining high-quality reproduced images suitable for news gathering for broadcasting, and particularly provides a dubbing method in which deterioration in dubbing image quality is extremely small. .

According to the present invention, it is possible to obtain high quality images and good dubbing characteristics even with a cylinder diameter and cassette that are the same or smaller than those of the VHS system VTR mentioned above, and the VTR is smaller and lighter than the conventional ENG VTR. can do.

The present invention will be explained in detail below.

FIG. 3 shows the arrangement of a head on a cylinder according to the present invention, FIG. 4 shows a front view of the head, FIG. 5 shows an example of a recording pattern, and FIG. 6 shows a block diagram of an embodiment of the invention.

In Figures 3 and 4, A, A', and B,
B' represents two sets of heads arranged at the same height and 180° apart on the circumference of the cylinder.

The heads A and B form the video tracks T _A and T _B shown in FIG. 5, and the heads A' and B' form the video tracks T _A ' and T _B ', which alternately form the video tracks. . In Figure 4, T _A and T _B are the track widths of heads A, A', B, and B', respectively.
T _P represents track pitch, and T _S represents space.
Now, the cylinder diameter, rotation speed, x, y values, T _A ,
If the values of T _B and T _S , the tape speed, and the angle formed by the tape and the recording trajectory are appropriately determined, a recording pattern as shown in FIG. 5 will be obtained. To give an example, a VTR that is set as T _A > T _B , has a cylinder with the same diameter as a VHS system VTR, and is capable of recording approximately 20 minutes on a VHS cassette.
can be configured.

Now, one embodiment of the recording and reproducing system for obtaining high quality according to the present invention is shown in FIG. 6 and will be described in detail. In FIG. 6, 1 is a luminance signal input terminal. 2 is the color difference input terminal of the color signal. For example, the RY signal or the I signal. This will be explained below as an I signal. 3 is another color difference signal input terminal for color signals. For example, it is a BY signal or a Q signal. This will be explained below as a Q signal. Each signal input terminal 1, 2, and 3 corresponds to the output of the color camera in the portable VTR for news reporting shown in FIG. 2, and is a wideband luminance signal, I signal, and Q signal.

Now, the luminance signal from this luminance signal input terminal 1 is band-limited by a low-frequency triple wave generator 4 that limits the band to, for example, 4MHz, and then a circuit (not shown) for clamping the separated luminance signal and a high-frequency The signal is passed through an emphasis circuit that emphasizes frequency components and a circuit that clips the signal to a level corresponding to the highest recordable frequency, and then the next FM modulator 7 converts the signal to, for example, 4.4~
FM modulated with a frequency deviation of 6.0MHz,
After being amplified by the recording amplifier 10, the video head 1
5, the spectrum is recorded on the recording medium as shown in FIG. 7A.

On the other hand, the I signal from the color difference signal input terminal 2 is, for example,
The band is limited by a low-pass filter 5 with a 1 MHz band, and after passing through a clamp circuit, an emphasis circuit, a clip circuit, etc. similar to the luminance signal described above, the FM modulator 8 filters the signal with a frequency deviation of, for example, 5 to 6 M.
Hz, is band-limited by a bandpass filter 11 to approximately 3MHz to 8MHz, and is guided to an adder 13.

Furthermore, Q from another color difference signal input terminal 3
The signal is passed through a low-pass filter 6 with a band of 0.5MHz, for example.
After passing through a clamp circuit, an emphasis circuit, a clip circuit, etc. similar to the luminance signal described above, the signal is FM modulated by the FM modulator 9 so that the frequency deviation is, for example, 0.75MHz to 1.25MHz. Adder 1 to approximately 2MHz with low-pass filter 12
3, the signal is added to the FMI signal, amplified by the recording amplifier 14, and recorded on the recording medium by the video head 16 with a spectrum as shown in FIG.

The video head 15 for the luminance signal is the head A, A' in FIG. 3, and the video head 16 for the precolor signal is the head B, B' in FIG. 3. By recording in this way, the track width of the luminance signal can be increased, and since the color signal is not superimposed, high S/N,
High-resolution playback images can be obtained. Also, the track width of the chrominance signal is narrow, but the band is I
The signal is about 1/4, and the Q signal is about 1/8, and the triangular noise caused by FM modulation is correspondingly reduced, making it possible to obtain a reproduced color signal with a high S/N ratio.

During reproduction, the FM modulated luminance signal reproduced from the video head 15 is amplified by the preamplifier 17, and although not shown, a limiter circuit removes amplitude fluctuations due to uneven hitting of the video head, and the FM modulated luminance signal is amplified by the FM modulator 18. A reproduced luminance signal is obtained by a low-pass filter 19 with a band of about 4 MHz. On the other hand, the color signal reproduced from the video head 16 is amplified by a preamplifier 21 and guided to a bandpass filter 22 and a low-pass filter 23.
The FM modulated I signal and the FM modulated Q signal are separated.
These two signals each pass through limiter circuits similar to those for the luminance signal, and are FM demodulated by FM modulators 24 and 25 and low-pass filters 26 and 27.
A reproduced Q signal is obtained. The timings of the obtained reproduced I signal, reproduced Q signal, and reproduced luminance signal are adjusted by timing adjustment delay devices 28 and 20 so that the time timings match, and are connected to an NTSC encoder 30. As shown in FIG. 3 or 4 of the present invention, since the luminance signal and the chrominance signal are recorded in separate heads, there is a problem that the time axis fluctuations experienced during reproduction differ between the luminance signal and the chrominance signal.
To solve this problem, the NTSC encoder 30
means for quadrature two-phase modulation of the I signal and the Q signal, means for superimposing the reproduced luminance signal on the quadrature two-phase modulated signal, and a subcarrier frequency used for the quadrature two-phase modulation. By using means for modulating _{the SC} (3.58MHz in NTSC) with a signal that creates _{an SC} that is phase-synchronized with at least the horizontal synchronization signal of the reproduced luminance signal, instead of using the crystal oscillator used in conventional encoders, the reproduced luminance signal The reproduced color signal is synchronized with the time axis fluctuation of In this way, the luminance signal and color signal are frequency interleaved within a band of about 4 MHz, similar to current color television signals, and a color video signal with time axis fluctuation is obtained at the VTR output end 31. For example, a stable color video signal can be obtained from the signal at the output terminal 31 using the TBC shown in FIG. It will be done.

Further, the luminance signal whose time timing matches,
The I signal and Q signal are connected to another VTR output terminal, that is, a dubbing output terminal 29.

Thus, when recording and reproducing are performed using the methods shown in FIGS. 2, 3, and 6, the following advantages arise.

In the luminance signal, the part subject to band limitation is the low-pass filters 4 and 19 in Figure 6, but the band is approximately
Since it is 4MHz, there is virtually no band restriction.
Furthermore, regarding the band of the electromagnetic conversion system after FM modulation, as can be seen from Figure 7A, for example, the band X from the frequency corresponding to the pedestal of the luminance signal is
4MHz or higher and not subject to band restrictions. Furthermore, since recording can be performed with a wider track width, a high S/N ratio can be ensured. Therefore, a reproduced luminance signal with high resolution and high S/N can be obtained.

For color signals, since the color difference signal is FM modulated, the band is much narrower than that of the luminance signal, so even if the track width is narrow, the S/N is high (for example, the above-mentioned
50 dB or more even for VHS format VTRs), and when recording on the recording medium, it is recorded without including amplitude and phase, so there is no uneven saturation or hue of the color signal.

When performing two-frequency recording by superimposing two color difference signals on one channel as in this color signal recording, third-order distortion caused by the hysteresis characteristic of the tape head system becomes a problem. The component is 3 _Q , where the carrier frequency of the Q signal _{is Q} and the carrier frequency of the I signal is _I.
and _I ±2 _Q. If such components exist within the I and Q bands, the FM demodulated I
Or it appears as beat disturbance in the Q signal. However, although the explanation of these components will be omitted here,
The spectrum arrangement shown in Fig. 7B is used, and during playback, as shown in Fig. 6, bandpass filter 22, low-pass filter 23, 2
6 and 27 so that it is outside the band or attenuated, so there is no problem.

Considering the third-order distortion mentioned above, a narrow-band color difference FM signal placed at a low frequency has fewer unnecessary components, so the FM signal of the Q signal
It is desirable that the modulated wave be on the lower frequency side compared to the FM modulated wave of the I signal.

Now, dubbing of signals recorded and reproduced in this manner will be described. To perform normal dubbing
The signal at the VTR output end 31 is connected to the input end of another VTR, but in the case of the one in which the luminance signal and the color difference signals of the I signal and Q signal are input, as in this embodiment, the signal is connected to the input end of another VTR. Brightness signal by decoder,
It is necessary to separate the I signal and Q signal. but,
Regarding luminance signal separation, if the luminance signal is separated using a low-pass filter with a 3MHz band, there is no point in obtaining a high-resolution signal. If you try to obtain a luminance signal in the 4MHz band, it can be separated using a comb filter using a 1H (one horizontal period) delay line, but a big problem arises in that the vertical resolution decreases. A similar problem occurs with color signals, and when creating a continuous wave that is phase-synchronized with the reproduced burst signal for decoding, the output end 31 has time axis fluctuations, so it is difficult to completely The problem arises that it is substantially difficult to create a continuous wave that follows. In view of these points, signal processing during dubbing, which is the main part of the present invention, will be explained using FIG. 8.

In FIG. 8, the same numbers as in FIG. 6 indicate the same operations. 32 shows a part of Figure 6 necessary for dubbing VTR1. 33 is a detailed diagram of the vicinity of the input section of FIG. 6 necessary for dubbing of the other VTR 2, 29a, 29b, and 29c are the luminance signal of the dubbing output terminal 29 of FIG. 6, the I signal,
The Q signals are shown respectively. 34, 35, 36
is the dubbing signal input terminal of VTR2, and the luminance signal,
The I signal and Q signal are shown respectively. The switches 37, 38, and 39 each have a luminance signal, an I signal,
This is a switch that switches the Q signal between the signal from the camera and the dubbing signal, and the figure shows the connection when dubbing. 40, 41, 42, and 43 are time timing delay devices.

The I signal and Q signal of the luminance signal and color difference signal with the same time timing regenerated from the VTR 1 of 32 are obtained at the dubbing output terminals 29a, 29b, 29c, respectively, and the luminance signal input terminal 34, 29a and the luminance signal input terminal 34, 2
9b and the I signal input end 35, and 29c and the Q signal input end 36 are connected by cables. This input end 34,
The three signals from 35 and 36 are transmitted through the camera and dubbing switch 37, 38, and 39 during dubbing.
-c becomes conductive, and the luminance signal is FM-modulated by the FM modulator 7 via the timing adjustment delay device 42. This FM modulated signal is connected to 10 recording amplifiers in FIG.

The I signal is passed through a timing adjustment delay device 43.
FM modulation is performed by an FM modulator 8.

The Q signal is FM modulated by an FM modulator 9.

The timing adjustment delay devices 42 and 43 are inserted so that the time timings match when recording is performed by the video heads 15 and 16.
Camera, dubbing switch 37, 38, 3
9 to the video head, time delays occur in the bandpass filter 11 and the low-pass filter 12 after the FM modulator for the I and Q signals, and usually the low-pass filter The delay time of No. 12 is longer. Therefore, the delay devices 43 and 42 for timing adjustment are installed to achieve the delay time, but if a group delay corrector is installed in the bandpass filter 11 or the low-pass filter 12, this principle does not always apply. However, in that case, the timing adjustment delay device can be appropriately placed between the camera dubbing switch and the FM modulator for the three signals so that they match the recording conditions with the video head.

Further, it is not always necessary to match the recording state with the video head, and a timing delay device may be installed so that the timing is a certain predetermined time.

With this configuration, the FM demodulated luminance signal, I signal, and Q signal with time axis fluctuations can be input to the FM modulator of the other VTR, and there is no image quality deterioration during that time. After performing such dubbing several times, the final output from the VTR can be performed using the color video signal output terminal 31 of the NTSC encoder 30 shown in FIG. In FIG. 8, when a camera signal is used, conduction is established between b and c of camera dubbing changeover switches 37, 38, and 39. In this case, the luminance signal is passed through a low-pass filter 4 to a band of about 4 MHz.
The I signal is limited to about 1 MHz by a low pass filter 5, and the Q signal is limited to about 0.5 MHz by a low pass filter 6. Therefore, since the Q signal has the most time delay, the timing adjustment delay devices 40 and 41 are used to match the delay time.

If such a dubbing method is used, the recording and reproducing method of the present invention will be made most effective, and furthermore, the deterioration of the dubbing image quality will be minimized.

In the description of the embodiment, a case has been described in which the I signal and the Q signal of the color difference signal are frequency-modulated and multiplexed, but the present invention is not limited to such a case. The signal obtained by adding the time-axis compressed signal may be frequency-modulated and recorded.

This method will be briefly explained using FIG. 9. In Fig _. 9, n ₁ , n ₂ ... are the horizontal line numbers, I ₁ , I ₂ , ... are the information of the horizontal lines of the I signal, and Q ₁ , _{Q 2 ...} are the information of the horizontal lines. Q signal n ₁ , n ₂ ...
...Indicates horizontal line information. A shows the luminance signal of each line, B shows an I signal of each line with a band of, for example, 1 MHz, and C shows a Q signal of each line with a band of, for example, 0.5 MHz. These B and C signals can be converted to a CCD, for example.
(charge coupled device) and other charge transfer elements, and send the I signal to 2/3H (H: 1 horizontal scanning period)
If you add the signals read out in a time of
It is possible to obtain one time-base compressed color difference signal D in the Hz band and in which the I signal and Q signal do not overlap in time. FM these two signals with one carrier wave.
By demodulating and recording, and performing FM demodulation during playback, the second reproduced color difference signal can be obtained.

By extending the time axis of this one color difference signal and performing the operation opposite to recording, it is possible to obtain the I signal B and Q signal C, and these I signal and Q signal are shown in Fig. 6, 30.
Quadrature modulated with NTSC encoder. Now, in dubbing using this recording method, the above-mentioned 1.
If two reproduced color difference signals, that is, signals that have been time-base compressed, are used as signals for dubbing, only one cable is required for dubbing the color signals, and dubbing output is obtained without deterioration in image quality. Also, as can be seen from Figure 9, the color difference signal is delayed by 1H with respect to the recording luminance signal, so to compensate for this, the reproduction luminance signal must be
Needless to say, this problem can be easily solved by delaying the luminance signal by 2H or by delaying the luminance signal by 1H during recording and playback.

In this case, the color signal can be recorded with one frequency modulated wave, so there is no problem with the third-order distortion mentioned above. Other methods may also be used. In other words, the color difference signal of the color signal is subjected to signal processing suitable for recording, includes means for frequency modulating with one or more carrier waves, and means for frequency modulating the luminance signal, and a signal that is frequency demodulated from the reproduced signal. The reproduced luminance signal and reproduced color difference signal are used as dubbing input for the next VTR.

Also, during dubbing, it is desirable to prevent the signal from passing through the low-pass filters 4, 5, and 6 as shown in FIG.
The signal may be connected to a low-pass filter and passed through a low-pass filter.

As described above, according to the present invention, the luminance signal is frequency-modulated and recorded, and the color difference signal of the color signal is frequency-converted using one or more carrier waves and recorded and reproduced, thereby achieving the above-mentioned VHS system VTR
It is made up of a head cylinder that is about the same size as the original, and is small and lightweight, making it possible to obtain high-quality reproduced signals for both luminance and color signals. In particular, only during the final transmission, the demodulated luminance signal and chrominance signal are encoded and output as an NTSC color video signal, and during dubbing, the demodulated baseband luminance signal and chrominance signal are input to another VTR as they are. By using the signal as a signal, deterioration in image quality due to dubbing can be reduced and good dubbing image quality can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a recording signal spectrum of a conventional VTR. Figure 2 is a system diagram explaining ENG. FIG. 3 is a plan view showing the head arrangement in an embodiment of the video signal recording/reproducing apparatus according to the present invention, FIG. 4 is a front view of the same, and FIG. 5 is a diagram showing an embodiment of the recording pattern according to the present invention. FIG. 6 is a basic block diagram of the recording/reproducing system of the present invention, FIG. 7 is a diagram showing the recorded signal spectrum of the main part of FIG. 6, FIG. 8 is a diagram explaining the dubbing method of the present invention, and FIG. FIG. 7 is a principle explanatory diagram showing another example of recording color signals according to the present invention. 1... Luminance signal input terminal, 2, 3... Color difference signal input terminal, 4, 5, 6, 12, 19, 23, 2
6,27...Low pass filter, 7,8,9...FM modulator, 10,14...Recording amplifier, 17,21...
...Preamplifier, 18,24,25...FM demodulator, 28,40,41,42,43...Time timing delay device.

Claims (1)

[Claims] 1. Frequency modulation of a luminance signal, frequency modulation of at least one or more carrier waves using a color difference signal, recording of each, and frequency demodulation of each of the frequency modulated signals at the time of reproduction, and reproduction. In a video signal recording and reproducing apparatus that obtains a luminance signal and a reproduced color difference signal, uses the reproduced color difference signal to obtain a color signal that is quadrature-phase modulated, and obtains a color signal by superimposing this color signal and the reproduced luminance signal as a color video signal, comprising: A video signal recording and reproducing device characterized in that a demodulated reproduced luminance signal and a reproduced color difference signal are used as signals for dubbing. 2 Frequency modulation of two color difference signals with two carrier waves with different frequencies, superimposition and recording of these modulated signals, frequency demodulation of each during playback, 2
2. The video signal recording and reproducing apparatus according to claim 1, wherein two reproduced color difference signals are obtained, and these reproduced color difference signals and reproduced luminance signals are used as signals for dubbing. 3 Compress the two color difference signals in time, mix the compressed two signals so that they do not overlap in time, convert them into one color difference signal, frequency modulate with one carrier wave, and record. 2. The video signal recording and reproducing apparatus according to claim 1, wherein during reproduction, one color difference signal which has been subjected to frequency demodulation and which remains time-base compressed and the reproduced luminance signal are used as signals for dubbing. 4. Claims 1, 2, or 4, characterized in that the dubbing signal is a signal in which the time timings of the reproduced luminance signal and one or more reproduced color difference signals are set to have a predetermined relationship. The video signal recording and reproducing device according to item 3. 5. A switching device is installed in the recording system of the video signal recording and reproducing device up to frequency modulation, and when dubbing,
Claim 1, characterized in that the dubbing signal of another video signal recording and reproducing device is switched at a predetermined time timing in a state where the dubbing signal is not band-limited and is recorded in a video head. The video signal recording and reproducing device described in .