JPH065937B2 - Video signal recording method, video signal recording apparatus, and recording / reproducing apparatus - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a video signal recording method for recording a video signal of a predetermined period T by dividing it into a plurality of parallel slant tracks of a tape during the period of T. The present invention relates to a video signal recording device and a recording / reproducing device.

[Background of the Invention]

The development of high-definition television systems such as NTSC and PAL, which have much higher definition than current televisions, is under way. In order to make the resolution in the vertical and horizontal directions more than twice the current resolution, the signal band is as high as 30 MHz for both Y (luminance signal) and C (chromaticity signal). In order to transmit this signal in a band as small as possible (about 8 MHz), it has been proposed to perform offset sampling between scanning lines and frames, the contents of which are, for example, the Technical Report of the Television Society of Japan TEBS95-2 ('84). March).

This band-compressed signal is sent to the PC within the vertical blanking period.
An M audio signal, a zero level reference signal of a chromaticity signal, a reference signal for horizontal sync separation, etc. are multiplexed. On the other hand, the horizontal blanking period is as short as 0.7 μsec and has a positive sync signal of the same polarity as the video signal.

The rotary head helical scan VTR that records and reproduces such a video signal has the following problems. 8 MH above
When recording and reproducing the z band with a small device such as a home VTR, one vertical period is divided into a plurality of tracks for recording due to the diameter of the cylinder in which the rotary head is mounted. There is no choice but to adopt the segment recording method. For this reason, it is necessary to insert a time axis correction circuit (TBC) in the reproduction circuit for correcting the skew generated when the tracks are switched. Conventionally, this skew correction is performed by making the phase of the horizontal synchronization signal continuous before and after the track switching immediately before the horizontal synchronization signal (front porch without video). Therefore, considering the amount of skew generated in a normal home VTR,
It was necessary to secure several μsec as the period of the front porch. However, if there is only about 0.7 μsec in the entire horizontal blanking period, there is a problem that scratches (lack of signal) occur on the reproduced image during correction.

Also, for example, to stabilize the zero level of the chromaticity signal,
Although it is necessary to clamp the video signal to a certain level, the reference signal that gives the timing of this clamp is within the vertical blanking period as described above. Therefore, when there are a plurality of skew points in one vertical period as in the reproduction of the segment type VTR, the normal clamping is performed from the first skew occurrence point to the next vertical blanking period. However, there is also a problem that the zero level of the chromaticity signal cannot be detected.

However, the development of VTRs for high-definition televisions has a short history, and measures for solving these problems have not yet been disclosed.

[Object of the Invention]

An object of the present invention is to solve the above problems and provide a technique capable of performing good time axis correction, clamp operation, and the like when reproducing a video signal.

[Outline of Invention]

For the above-mentioned purpose, in the present invention, at least two rotary heads, which are arranged at a predetermined angle from each other with respect to the center of rotation, form an overlap portion which faces the tape at the same time. In the method of recording a video signal divided into a plurality of tracks for recording, the input video signal is divided into a plurality of signal blocks in the period of T, and the time axis conversion is performed for each of the signal blocks. A recording video signal having a redundant signal for an arbitrary period is formed between them, at least the recording video signal for each signal block thereof, at a timing when at least a part of the redundant signal is located in the overlapping portion of the track, It is characterized in that the redundant signal and the corresponding tracks are sequentially recorded.

Example of Invention

Next, an embodiment of the present invention will be described with reference to the circuit block diagram of FIG. 1 and the signal waveform diagram of FIG. The figure shows 2 heads 4
This is an embodiment in the case of a segment recording type VTR.

The video signal of the format shown in FIG. 2 (a) is input to the input terminal 1. In FIG. 2 (a), V is a video signal (including Y, C, and horizontal synchronizing signals), V-BLK is a vertical blanking period, and the audio signal indicated by A is V during a certain period of V-BLK. It is multiplexed. The audio signal is removed from the signal from the input terminal 1 by the gate circuit 2 driven based on the vertical blanking phase, and becomes the signal shown in FIG. 2 (b). After that, it becomes a digital signal in the AD converter 3. A signal through this signal and a signal through a delay circuit 4 having a constant delay time (for example, 1H; H is a horizontal period) formed of, for example, a shift register, and a signal through a similar delay circuit 5, and further a delay circuit. The signals via 6 are applied to the switching circuit 7, respectively. The switching circuit 7 is driven by the control signal from the input terminal 8. In the case of the two-head helical scan type VTR, this control signal is a known head switching signal (which indicates which head is on the magnetic tape, which is synchronized with the rotation phase of the rotary cylinder as shown in FIG. 2D). .) Should be used. Then, the switching point comes to an appropriate point in the V-BLK, and after that, it is switched to l ₁ , the head is switched to l ₂ , then l ₃ and l _4, and so on. Then, if the output is returned to the analog signal by the DA converter 9,
The signal shown in FIG. 2 (c) is obtained at the output terminal 10. This is F
It becomes an M-modulated signal and is recorded on the magnetic tape.

As indicated by α in FIG. 2 (c), for example, 1H (delay circuits 4, 5, 5) centered around the head switching point of the recording signal.
A signal-free period corresponding to a delay time of 6) is produced, and a sufficient time margin for skew correction during reproduction can be secured. Moreover, since this no-signal period appears in synchronization with the phase of the head switching signal even during reproduction, it is possible to easily detect the timing at which the correction operation should be performed. As a result, the video signal immediately before the vertical blanking period is delayed by 3H in the above example compared to the input original signal shown in FIG. 2 (a), but the redundancy is increased by the amount corresponding to the removal of the audio signal. If the blanking period is shortened by 3H, it is possible to restore the time relationship that matches the original signal input for each vertical blanking.

As mentioned above, this is a 4-segment recording type VTR.
However, it goes without saying that the same method can be used when the number of segments is different.

Further, it is not necessary to limit the delay time of the delay circuits 4, 5, 6 to 1H. The point is that the time margin for skew correction can be ensured, and any range may be used as long as the audio signal is removed and the time relationship can be returned to the original signal input with the video signal for each vertical blanking. Delay circuit 4, 5,
The delay times of 6 may be different from each other.

Further, it is not essential to delay the signal after digitizing it through the AD converter 3, and the delay processing may be performed as it is as an analog signal. Further, the digital signal output from the switching circuit 7 may be directly modulated and recorded on the magnetic tape without passing through the DA converter 9.

On the other hand, the no-signal period of, for example, 1H is set to α in FIG. 2 (c).
It is effective to set the potential to a constant potential as shown in, and clamp it to a constant DC potential in the signal processing circuit. Especially when the horizontal blanking period is extremely short, the effect is great when there is not enough time for sufficient clamping, and as described above, it is effective in stabilizing the zero level of the chromaticity signal. is there. The timing for performing this clamping can be easily detected from the head switching signal even during reproduction.

In the above description, the recording method of the audio signal is not mentioned at all, but this will be described with reference to FIG. 3 by taking the case of the two-head helical scan type as an example. In the figure, the input terminal 1 to the DA converter 9 may be the same as in FIG. DA
The output of the converter 9 becomes an FM modulated signal by the FM modulator 11,
It is added to one end of the switching circuits 12a and 12b. The signal from the input terminal 1 is applied to the gate circuit 13, where the PCM-converted audio signal portion is taken out based on the phase of vertical blanking. Of course, the gate circuits 2 and 13 may be combined into one switching circuit. Further, a modulated wave suitable for recording on a magnetic tape is made by the PCM processor 14 and applied to the other ends of the switching circuits 12a and 12b. The two switching circuits 12a and 12b are each driven based on the head switching control signal from the input terminal 8. The output is supplied to two video heads 16a, 1 via two recording amplifiers 15a, 15b.
Add to 6b. The magnetic tape 17 is wound around the rotary cylinder on which the video heads 16a and 16b are mounted, slightly more than 180 °. In this case, two video heads 16 are used as in this embodiment.
If the switch circuits 12a and 12b and the recording amplifiers 15a and 15b of different systems are provided to the a and 16b, respectively, the video is recorded in the above 180 ° section and the sound is recorded in the remaining section on the extension thereof. Can be realized.

In the case of the segment recording VTR, it is arbitrary whether the audio signal is recorded on the extension of each video track or every other audio signal, and in any case, it can be realized by converting the time axis by the PCM processor 14. Similarly, the processor 14 may be provided with a conversion function for giving redundancy to the audio signal, for example.

The above is the case of using the audio overlap recording, but it is not limited to this, and the output of the gate circuit 13 described above is returned to the analog baseband signal, and bias recording is performed on the magnetic tape end portion with the fixed head. Is also good.

Next, an embodiment for reproducing the recorded signal as described above will be described with reference to the circuit block diagram of FIG. 4 and the signal waveform diagram of FIG. This figure shows the case of reproducing the recorded signal based on the embodiment of FIG. 3, and the video heads 16a, 16b and the magnetic tape 17 may be the same as those of FIG. The operation will be described below.

The reproduction outputs of the video heads 16a and 16b are amplified to appropriate levels by the reproduction amplifiers 18a and 18b, and then added to the switching circuits 19a and 19b. The switching circuits 19a and 19b are driven by a head switching signal synchronized with the rotational phase of the rotary head at the time of reproduction from the input terminal 31, and as a result, the video signal is output to the output of 19a and the above-mentioned is output to the output of 19b. Audio signals due to overlap recording appear separately.

The output of the switching circuit 19a is demodulated by the FM modulator 20 and added to the time axis correction circuit 21. The head switching signal is also guided to the correction circuit 21, which is synchronized with the no-signal period on the video track created during recording. On the other hand, since the skew is generated in the no-signal period by the signal processing at the time of recording, the correction circuit 21 can perform the skew correction based on the switching signal with a sufficient time margin. As a result, at the output of the correction circuit 21, it is possible to obtain the same video signal as that shown in FIG. 2 (c), as shown in FIG. .

Next, it becomes a digital signal in the AD converter 22, and this signal, a signal through the delay circuit 23 (same delay time as the delay circuit 6 in FIG. 3), and a delay circuit 24 (same delay time as the delay circuit 5). ) And a signal via the delay circuit 25 (same delay time as the delay circuit 4) are added to the switching circuit 26. The switching circuit 26 is also driven by the head switching signal, and is switched to f ₁ during the vertical blanking period and immediately thereafter, to f ₂ after the next head switching point, and then to f ₃ and f ₄ . , Its output is DA converter 27
By returning to an analog signal with, a video signal similar to that shown in FIG. 2 (b) can be obtained as shown in FIG. 5 (b). The output of the DA converter 27 is added to the adder 28.

On the other hand, the output of the previous switching circuit 19b is the PCM processor 29.
The signal is demodulated at and returned to the same signal as the input signal at the time of recording. Further, after properly performing phase matching with the signal indicating the vertical blanking period after the time axis correction from the input terminal 30, it is added to the adder 28.

The video signal and the audio signal are added in the adder 28, and the signal shown in FIG. 5 (c) is output to the output terminal 32. This is the same as the recording input signal shown in FIG. 2 (a), and it can be seen that the intended recording / reproducing operation can be completed.

As described above, by providing a no-signal period at the head switching point where the track changes at the time of recording for recording, the no-signal period can be detected during reproduction based on the phase of the head switching signal. Skew correction can be performed with a time margin. Further, even in a skewed state before the time axis correction, clamping can be performed with a sufficient time margin by using this no-signal period based on the phase of the head switching signal. The zero level of can be stabilized.

〔The invention's effect〕

As described above, according to the present invention, a video signal having an extremely short horizontal blanking period is recorded in the segment recording type VTR.
Also in the case of recording by (1), it is possible to obtain a sufficient time margin to satisfactorily correct the skew generated at the head switching point during reproduction, and it is possible to prevent the lack of a signal on the reproduced image.

Further, for this purpose, by clamping the no-signal period formed at the time of recording, it is possible to perform clamping with a sufficient time margin even in a skewed state, for example, to stabilize the zero level of the chromaticity signal. be able to.

Further, there is an effect that the timing for performing the skew correction and the clamp can be easily detected from a known head switching signal.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an embodiment of the present invention, FIG. 2 is a signal waveform diagram for explaining the present invention, and FIGS. 3 and 4 are circuit block diagrams showing an embodiment of the present invention. FIG. 5 is a signal waveform diagram for explaining the present invention. 2 ... Gate circuit, 3,22 ... AD converter 4,5,6,23,24,25 ... Delay circuit 7,26 ... Switching circuit, 9,27 ... DA converter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuo Mohri 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside the Home Appliance Research Laboratory, Hitachi, Ltd. (56) Reference JP-A-58-1807 (JP, A) JP 49-131107 (JP, A) JP-A-59-111484 (JP, A)

Claims (6)

[Claims] 1. An overlapping portion in which at least two rotary heads arranged at a predetermined angle from each other with respect to a center of rotation are simultaneously opposed to the tape, and a video signal having a period T is transmitted to a plurality of parallel oblique tracks of the tape. In the recording method of the video signal to be divided and recorded into, the input video signal is divided into a plurality of signal blocks in the period of T, and time axis conversion is performed for each signal block to perform an arbitrary period between the signal blocks. Forming a recording video signal having a redundant signal of at least the recording video signal for each signal block, together with the redundant signal at a timing when at least a part of the redundant signal is located in the overlapping portion of the track. A recording method of a video signal, wherein the recording is sequentially performed on each of the corresponding tracks. 2. At least two rotary heads arranged at a predetermined angle from each other with respect to the center of rotation are formed with an overlapping portion which faces the tape at the same time. A device having a structure for dividing and recording the input video signal into a plurality of signal blocks in the period of T; and a signal axis block for performing time-axis conversion for each signal block. Recording video signal forming means for forming a recording video signal having a redundant signal for an arbitrary period therebetween; at least the recording video signal for each signal block, and at least a part of the redundant signal in the track overlap portion Signal recording means for sequentially recording on the corresponding tracks along with the redundant signal at the timing of A video signal recording device characterized by: 3. The video according to claim 2, wherein said recording video signal forming means comprises means for multiplexing a signal of a predetermined potential or a predetermined reference signal during the period of said redundant signal. Signal recorder. 4. The signal recording means forms a recorded audio signal in a PCM code format including a predetermined code redundancy based on an audio signal input separately from the input video signal, and the recorded audio signal. 3. The video signal recording apparatus according to claim 2, further comprising means for occupying and recording a signal on a track in an area different from the area where the recording video signal is recorded. 5. At least two rotary heads, which are arranged at a predetermined angle from each other with respect to the center of rotation, are formed with an overlapping portion which faces the tape at the same time. In a device having a structure for recording the divided video signal and reproducing the video signal, a signal input means for inputting the video signal and an audio signal accompanying the video signal; Signal dividing means for dividing into signal blocks; recording video signal forming means for performing time-axis conversion for each signal block and forming a recording video signal having a redundant signal of an arbitrary period between the signal blocks; at least the above recorded video For each signal block, a signal is shared with the redundant signal at a timing when at least a part of the redundant signal is located in the overlapping portion of the track. A video signal recording means for sequentially recording on each of the corresponding tracks; a recording audio signal forming means for forming a recording audio signal based on the input audio signal; and at least the recording audio signal of the recording video signal. Audio signal recording means for occupying and recording on a track in an area different from the area to be recorded; video signal reproducing means for reproducing the video signal recorded by the video signal recording means; and recorded by the audio signal recording means An audio signal reproducing means for reproducing an audio signal which reproduces an audio signal; and after switching reproduction of the signal block within the period of the redundant signal between the signal blocks included in the reproduced video signal from the video signal reproducing means, A video signal processing that performs time-axis conversion for each signal block to remove the redundant signal and restores and outputs a signal of the same format as the input video signal. Audio signal processing means for processing the reproduced audio signal from the audio signal reproducing means and for restoring and outputting a signal of the same format as the audio signal input at the time of recording. Characteristic video signal recording / reproducing apparatus. 6. The recorded voice signal forming means is configured to form a recorded voice signal in a PCM code format including a predetermined code redundancy on the basis of the inputted voice signal. A video signal recording / reproducing apparatus as described in.