JPH0466154B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is applicable to a video signal recording/reproducing device capable of obtaining high-quality reproduced video signals, particularly in the fields of news gathering (ENG), program production (EFP), and VTR. The present invention relates to an available video signal recording and reproducing device.

Conventional configuration and its problems At present, magnetic recording and reproducing devices (hereinafter referred to as VTR)
The mainstream is the helical scan type, in which a rotating head forms an image track diagonally on the tape. In particular, home VTRs are becoming smaller and more dense. For example, in a VHS system VTR, a video signal is recorded diagonally onto a 1/2 inch tape using two video heads arranged at 180 degrees to each other on a rotating cylinder with a diameter of 62 mm. Also, in broadcasting VTRs, news gathering (ENG) portable
For VTRs, there is a strong need for smaller size and lighter weight, and 3/4 inch U
Standard VTRs have also made considerable inroads. VTR for ENG
In addition to being small and lightweight, it is also required to have high image quality because it is used for broadcasting. The 3/4-inch U-standard VTR has a cylinder diameter of 110 mm and a tape width of 3/4 inch, so there are limits to miniaturization. Since a method is used in which a carrier chrominance signal that has been reduced and is superimposed is removed, the bands of the luminance signal and chrominance signal are limited, and the image quality is not necessarily sufficient for broadcasting. In Figure 1
The recording pattern of an NTSC 3/4 inch U standard VTR is shown. In Fig. 1, T _W , T _P , and T _S represent the video track width, video track pitch, and space, respectively, and approximately T _w = 85 μm, T _P = 137 μm,
T _S =52 μm.

In consideration of the above points, a new type of device was developed that records luminance signals and color signals on separate tracks in order to obtain reproduced images of high quality with a small size and light weight. According to this system, high-quality images can be obtained even with a cylinder diameter and cassette of the same size as a VHS system VTR, and the system can be made smaller and lighter than conventional ENG VTRs.

FIG. 2 is a plan view of the head arrangement on the cylinder used in the apparatus, FIG. 3 is a front view of the head, FIG. 4 is a diagram showing an example of the recording pattern by the head, and FIG. 5 is a diagram showing the head arrangement. FIG. 6 shows a waveform diagram of the main part of FIG. 5, FIGS. The recording method according to the following is explained below.

In FIGS. 2 and 3, A, A' and B, B' represent two sets of heads located at the same height and 180 degrees apart from each other on the circumference of the cylinder. Also, A, A', B, and B' in FIG. 4 represent trajectories drawn by heads A, A', B, and B', respectively. Figures 3 and 4
In the figure, T _A and T _B are A, (A'), B, (B') respectively.
TP is the track width of the head, and T _P is the track pitch.
T _S represents space. Now the diameter of the cylinder,
rotation speed, x and y values in Figure 3, T _A ,
If the values of T _B and T _S , the tape speed, and the angle between the tape and the recording trajectory are determined appropriately, the trajectory shown in Figure 4 can be obtained with the head arrangement shown in Figures 2 and 3. . To give an example, VHS system VTR
It is possible to construct a VTR that has a cylinder with the same diameter as the VHS cassette and is capable of recording approximately 20 minutes.

One method for recording and reproducing color video signals with the recording and reproducing apparatus described above is to record a luminance signal (frequency modulation) in the A (A') head and to transmit a chrominance signal (frequency modulation) in the B (B') head. There is a way to record it. In this way, the track width of the luminance signal can be increased, and since the chrominance signal is not superimposed, the band can be widened, and re-images with high S/N and high resolution can be obtained. In addition, color signals can be recorded by frequency modulating baseband signals (for example, R-Y signal and B-Y signal), so they can be recorded with high S/N over a wide band.
It is possible to obtain a playback signal of The device thus provides a device that is small, lightweight, and provides high quality images. In the example above, VHS
Constructed with a cylinder of the same diameter as a VHS system VTR, it is possible to record approximately 20 minutes on a VHS cassette, making it possible to construct a VTR for EGN that is smaller, lighter, and of higher quality than before.

In FIG. 5, 1 is a Y signal (luminance signal) input terminal, 2 is an RY signal input terminal, 3 is a B-Y signal input terminal, 4 is a time axis compressor, 5 and 6 are frequency modulators, and 7 , 8 is a recording amplifier, 9 and 10 are video heads, 11 and 12 are reproduction amplifiers, 13 and 14 are frequency demodulators, 15 is a time axis expander, 16 is a Y signal output terminal, and 17 is an RY signal output terminal. , 18 is B
-Y signal output terminal.

In addition, in FIG. 6, 1, 2, and 3 are the waveforms of the input Y signal, R-Y signal, and B-Y signal, respectively (a horizontal synchronization signal is added only to R-Y),
19 is the waveform of the output signal of the time axis compressor 4;
This is the waveform at each number in the figure. The Y signal applied to the Y signal input terminal 1 is modulated by a frequency modulator 5, amplified by a recording amplifier 7, and then recorded on a tape by a head 9. Y signal is approximately 4MHz
In order to record and reproduce this signal with good performance, the modulation frequency deviation is, for example, 4.4MHz to 6MHz.
It is set as follows. RY signal input terminal 2, B
-The R-Y signal and the B-Y signal applied to the Y signal input terminal 3 are processed by the time-base compressor 4, as shown in waveform 19 in FIG. The signal is compressed on the time axis and synthesized into the B-Y signal. This signal is modulated by a frequency modulator 6, amplified by a recording amplifier 8, and then recorded on a tape by a head 10. R-Y signal is approximately 1.5M
Hz, B-Y signal has a band of approximately 1.5MHz,
The signal obtained by compressing the time axis to 1/2 of each signal is R
- Approximately 3MHz in the Y signal section (denoted as -), B-
The Y signal part (denoted as -) has a band of approximately 3MHz. The frequency shift of this composite signal is, for example, 3.5M
Set between Hz and 5MHz. The tape pattern in which the Y signal and color signal are recorded by the two pairs of heads having the structure described above is as shown in FIG. In FIG. 4, A and A' are the recording trajectories of the Y signal, and B and B' are the recording trajectories of the color signal. During reproduction, the Y signal reproduced from the head 9 is amplified by a regenerative amplifier 11, demodulated by a frequency demodulator 13, and a reproduced Y signal is obtained at an output terminal 16. On the other hand, the color signal reproduced from the head 10 is amplified by a regenerative amplifier 12, demodulated by a frequency demodulator 14, and then by a time axis expander 15.
is expanded and separated into the original RY signal and BY signal, and the reproduced RY signal is output to the output terminals 17 and 18.
A B-Y signal is obtained.

However, in the above explanation, since a head with a structure as shown in Figs. 2 and 3 is used, self-recording may occur due to variations in the x value and adjustment accuracy in Fig. 3, during compatibility, and due to expansion and contraction of the tape. Even during re-timing, a time difference may occur between the reproduced Y signal and the reproduced color signal.

Therefore, it is necessary to add a timing detection pulse to the color signal to match the time difference between the reproduced Y signal and the reproduced color signal. At that time, one of the two color signals, for example, as shown in FIG.
It is sufficient to add a timing detection pulse only to R-Y as shown in FIG. This is because the two color signals are recorded on the same track.

As mentioned above, in FIG. 6, 1 is the luminance signal Y, 2 is the RY signal to which a timing detection pulse is added to match the timing with the luminance signal, and 3 is the B-Y signal. 19 is a signal obtained by compressing two color signals into one signal.
The RY signal is compressed into the first half, and the B-Y signal is compressed into the second half. FIG. 7 21 shows the pre-emphasized compressed signal, and FIG. 8 53 shows the − of FIG. 7 21.
An enlarged view of the blanking period of the signal, 54 is an enlarged view of the blanking period of the B-Y signal of 21,
PV indicates pedestal potential and CV indicates clamp potential.

Now, when the color signal is compressed as shown in Fig. 6, 19, the seventh
The position between the trailing edge of the timing detection pulse and the blanking period must be clamped as shown in FIG. However, when pre-emphasis is applied to this compressed signal, the trailing edge of the timing detection pulse becomes less straight as shown in FIG. 7, and the clamping potential becomes different from the pedestal potential, as shown in FIG. 8, 53. The blanking period is 11.12μsec, the horizontal synchronization signal is 4.7μsec, and the time from the start of blanking to the leading edge of the horizontal synchronization signal is 1.4μsec, so the period from the trailing edge of the horizontal synchronization signal to the end of blanking is 5.02μsec. Therefore, during compression, the clampable period is 2.51μsec. The width of the clamp pulse is required to be 1 μsec, so the trailing edge caused by the emphasis must settle down and become horizontal within 1.51 μsec from the trailing edge of the horizontal synchronizing signal.

However, in reality, the signal is not yet horizontal at the clamp position, and the clamped position is somewhat different from the pedestal position, as shown in FIG. 8, 53. As a result, when the reproduced video signal is observed with a vectorscope, the bright spot when there is no signal is shifted from the center.

Purpose of the Invention As described above, it is an object of the present invention to provide a video signal recording and reproducing device that eliminates the phenomenon of the clamp position shifting from the pedestal position and in which the clamp position does not always shift from the pedestal position regardless of the amount of emphasis. This is the purpose.

Composition of the Invention The video signal recording and reproducing device of the present invention compresses the chrominance signal so that the position of the pulse that detects the timing of the luminance signal and the chrominance signal is approximately in the center of the horizontal synchronization signal of the luminance signal, and compresses the timing detection pulse. This configuration is configured to clamp the blanking period of the color signal to which no color signal is added.

DESCRIPTION OF EMBODIMENTS FIG. 9 shows a block diagram of a video signal recording and reproducing apparatus according to an embodiment of the present invention. In FIG. 9, 22 is a Y signal input terminal, 23 is a R-Y signal input terminal, 24 is a B-Y signal input terminal, 25 is a Y signal pre-emphasis circuit, 26 is a sync signal separator, and 27 is a Y signal clamp circuit. , 28 is a Y signal clamp pulse generator, 29 is a frequency modulator, 30
is a recording amplifier, 31 is a Y signal recording head, 32
3 is a Y signal clamp pulse, 33 is a color signal clamp pulse generator, 34 is a color signal clamp pulse, 3
5 to 38 are variable delay lines, 39 is a compressed signal changeover switch, 40 is a compressed color signal, 41 is a pre-emphasis circuit for the compressed color signal, 42 is a signal obtained by emphasizing the compressed signal, 43 is a compressed signal clamp circuit, and 44 is a compressed signal clamp circuit. A compressed color signal clamped by a clamp circuit 43, 45 a frequency modulator for compressed color signals, 4
6 is a recording amplifier for compressed color signals, 47 is a head for recording compressed color signals, 48 is a control signal generation circuit for time axis compression, 49 is a PLL that generates a clock for driving a variable delay line, and 50 is a Y A synchronizing signal separated from the signal, 51 a switching signal for switching the compressed color signal, and 52 a variable delay line drive clock for compressing the color signal.

The Y signal is input from an input terminal 22, emphasized by a pre-emphasis circuit 25, clamped by a clamp circuit 27, frequency modulated by a frequency modulator 29, amplified by a recording amplifier 30, and recorded on a tape by a recording head 31.

The R-Y signal is input to the input terminal 23, and the B-Y
The signal is input to the input terminal 24 and input to variable delay lines 35 to 38, respectively. Next, a synchronization signal 50 is separated from the Y signal by a synchronization separator 26, and a variable delay line driving pulse 52 and a compressed signal switching signal 51 are generated from the synchronization signal 50 using a PLL 49 and a control signal generation circuit 48. . Variable delay line 35~
The signal compressed at 38 is switched by a changeover switch 39 to become one compressed color signal 40, which is emphasized by a pre-emphasis circuit 41, clamped by a clamp circuit 43, frequency modulated by a frequency modulator 45, and amplified by a recording amplifier 46. The color signals are recorded on the tape by the color signal recording head 47.

In addition, in FIG. 9, the synchronization signal is separated from the Y signal 22 to create a color signal clamp pulse, but the synchronization signal is separated from the R-Y signal 23 to create a color signal clamp pulse and a control signal. It's good to wear. Further, the Y signal clamp pulse generator 28 and the color signal clamp pulse generator 33 can be used in common to use the same clamp pulse.

FIG. 10 shows the timing of compressing color signals in the embodiment of the present invention. 10, 22 is the luminance signal Y, 23 is the RY signal, 24 is the B-Y signal, 4
0 is a color signal compressed in the order of -, -,
34 is a clamp pulse.

FIG. 11 shows an emphasis waveform of the compressed signal 40 shown in FIG. 10. Figure 11 22 is the Y signal, 4
2 is an emphasis waveform, 44 is a clamp circuit 43
The emphasis waveform is clamped by , and 34 is a clamp pulse. As shown in Figure 10, R-Y
From the leading edge of the timing detection pulse added to the signal
Color signal compression starts after 8μsec. The compression start position is changed by changing the clock switching position of the drive pulse 52. Then compressed −
The signals and - signals are arranged in the order of - and - to form one color signal 40. As a result, Figure 10 4
As shown at 0, the timing detection pulse of the - signal comes approximately near the center of the horizontal synchronization signal of the luminance signal. - The blanking period of the signal comes near the horizontal synchronization signal of the luminance signal. This compressed signal 40
When emphasis is applied to , the waveform shown at 42 in FIG. 11 is obtained. Since there is no timing detection pulse during the blanking period of this - signal, FIG.
As shown in , the blanking period is horizontal and equal to the pedestal potential, and even if a large amount of emphasis is applied, this blanking period is not affected. Therefore, the − blanking period of the compressed signal is set as the first
1. By clamping with the clamp pulse shown in FIG. 34, it is possible to obtain a compression signal that is not affected by emphasis and is clamped to a potential that always matches the pedestal potential.

Furthermore, as shown in FIG. 12, if compression is started 1.0 μsec before the leading edge of the timing detection pulse, the compression will be as shown in FIG.
By arranging the Y signal and the - signal in the order of - and -, the timing detection pulse can be brought approximately to the center of the horizontal synchronization signal of the luminance signal.

Effects of the Invention As explained above, in the video signal recording and reproducing apparatus of the present invention, the compressed signal is always clamped at a potential equal to the pedestal potential, regardless of the amount of emphasis, and when observed with a vector scope, a bright spot when there is no signal is detected. The deviation from the center disappears. In addition, the color signal clamp pulse can be created more easily than the Y signal synchronization signal, and furthermore, this color signal clamp pulse is
It can be used in common with the signal clamp pulse, and the same clamp pulse can be used for both the Y signal and the compressed color signal. Furthermore, since the clampable period is long, the accuracy of the clamp position does not need to be high.

[Brief explanation of the drawing]

Fig. 1 is a pattern diagram showing the recording pattern of a conventional VTR, Fig. 2 is a plan view showing the head arrangement of a video signal recording and reproducing device, Fig. 3 is a front view of the head, and Fig. 4 is a recording pattern by the head. A pattern diagram showing an example of the pattern, FIG. 5 is a block diagram of a recording method using the above-mentioned head, FIG. 6 is a signal waveform diagram for explaining a compressed signal in the same recording method, and FIG. 7 is similar to FIG. FIG. 8 is an enlarged view of the clamp portion thereof; FIG. 9 is a block diagram of a video signal recording and reproducing apparatus according to an embodiment of the present invention;
FIG. 2 is a signal waveform diagram for explaining the compressed signal in the present invention, and FIG. 11 is a waveform diagram when the compressed signal of FIG. 10 is pre-emphasized. 33...Color signal clamp circuit, 35-38...
Variable delay line, 39...Switch switch, 40, 50
... Compressed signal, 41 ... Pre-emphasis circuit,
43... Clamp circuit, 48... Control signal generation circuit, 49... PLL, 50... Synchronization signal, 51...
...Switching signal, 52...Drive pulse.

Claims (1)

[Claims] 1 Of the three components that form the video signal, the luminance signal component is compressed on the time axis in one pair of heads, while the other two color difference signal components are compressed on the time axis in units of a fixed period and time-division multiplexed to form one compressed color difference signal. In a video signal recording and reproducing apparatus that records on the other of a pair of heads and expands the compressed color difference signal in fixed time units during playback to obtain the original luminance signal and color difference signal,
means for adding a timing detection pulse to one of the color difference signals for matching the timings of the luminance signal and the color difference signal, and a position of the timing detection pulse between the two color difference signals to be synchronized with the luminance signal; a time-base compressor for time-base compressing and time-division multiplexing a color difference signal, and a time base compressor for compressing a color difference signal in a time domain and time-division multiplexing, and clamping a horizontal blanking period at the beginning of the compressed color difference signal with reference to a horizontal synchronization signal of the luminance signal component during recording; 1. A video signal recording and reproducing device comprising: means for recording and reproducing video signals.