JPH0744933A - Magnetic recording and reprpoducing device - Google Patents

Abstract

PURPOSE:To effectively prevent the disturbance in a picture at the time of discriminating a mode and changing the mode when the numbers of revolution of a drum of in recording mode and reporducing mode are different from each other by switching the mode after temporarily freezing an output video signal and releasing the freeze after switching over the mode. CONSTITUTION:At the recording time, the video signal inputted from an IN is A/D-converted 21 in the state where the modes of an A/D converter 21, a compression circuit 1 and error correction encoding circuit 2 are set based on the selected number of revolution of the drum, and is written in a memory 7 through the compression circuit 1. Then, the signal written on a magnetic tape is switched to an ATF signal or a digital video signal according to the phase of a rotary drum. On the other hand, at a reproducing time, the signal reproduced from the magnetic tape is amplified by a head amplifier 13 to be inputted to a reproducing equalizer circuit 12, an LPF 14 and a synchronizing signal detection circuit 17. When the numbers of revolution of the drum of the recording and the reproducing modes are different from each other, the mode is switched after the output video signal is freezed temporarily, and the freeze is released after the mode is ehanged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has two or more kinds of recording modes in which the rotational speed of a rotary drum is different, and particularly, in a helical scan type magnetic recording / reproducing apparatus (VTR), mode detection and mode transition during reproduction. It concerns the processing of time.

[0002]

2. Description of the Related Art Conventionally, in a VTR of this type having two or more types of recording modes, the rotational speed of a rotating drum (drum rotational speed) is constant as in the case of the VHS system, and a magnetic tape is used. It is known that the tape feeding speed is changed to record.

FIG. 5 shows an example of the configuration of such a conventional VTR. In FIG. 5, reference numerals 30 and 37 denote A / D converters for converting analog signals into digital data, and 31 denotes a TV signal for VHS recording format. Signal processing circuits for converting the signals into digital signals, 32 and 35 D / A converters for converting digital data into analog signals, 33 an FM modulation circuit for FM-modulating the video signals, and 34 recording the FM-modulated video signals. Recording equalization circuit for equalization, 36 is a signal processing circuit for converting a reproduced video signal into a TV signal, 38 is an FM demodulation circuit for returning an FM-modulated signal to the original, and 39 and 40 are reproduced signals. A reproduction equalization circuit for equalization, 41 is a servo circuit for controlling the tape feeding speed, 42 is a microcomputer, and 43 is a cycle measuring circuit for measuring the cycle of CTL.

In the above structure, the video signal is converted into digital data by the A / D converter 30, further converted into a signal of the VHS recording format by the signal processing circuit 31, and then an analog signal through the D / A converter 32. Is output as. Then, the signal modulated by the FM modulation circuit 33 is recorded through the recording equalization circuit 34.

At the time of reproduction, the signal from the reproduction equalization circuit 39 is demodulated through the FM demodulation circuit 38. Thereafter, the signal digitized through the A / D converter 37 is converted into a digital TV signal in the signal processing circuit 36 and output through the D / A conversion 35. In this case, to detect the recording mode during reproduction, the cycle of the CTL signal output from the reproduction equalization circuit 40 is measured with a specific clock and this is input to the microcomputer 42. In the microcomputer 42, the recording mode is determined according to the cycle of the CTL,
As a result, the reproduction mode is switched to the servo circuit 41.

[0006]

However, in the above-mentioned conventional magnetic recording / reproducing apparatus, the CTL signal written in the longitudinal direction of the magnetic tape at a constant cycle at the time of recording is measured at the cycle to reproduce the mode. I try to judge. For this reason, when only the drum rotation number is switched at the time of recording and recording is performed at the same tape speed, the cycle of the CTL signal is always constant at the time of reproduction, so that there is a problem that the mode discrimination becomes impossible. In addition, when the mode is changed after the mode is determined, the reproduction signal from the magnetic tape is continuously output, so that the reproduction screen is disturbed when the mode is changed.

In view of the above situation, the present invention always accurately and promptly discriminates a plurality of recording modes,
Another object of the present invention is to provide a magnetic recording / reproducing apparatus which obtains a proper screen when the mode is changed.

[0008]

Magnetic recording according to the present invention
The reproducing apparatus has two or more kinds of recording modes in which the rotating speed of the rotating drum is different. At the time of recording, the rotating head on the rotating drum writes a signal of a constant frequency to a part of the magnetic tape and reproduces it. Sometimes the recording mode is identified by detecting the frequency of this written signal, and if the recording mode and the playback mode are different, a freeze or fixed pattern image is output at the same time as the mode switching, and the mode transition is completed. At this time, the reproduced video signal of the magnetic tape is output again.

[0009]

According to the magnetic recording / reproducing apparatus of the present invention, at the time of recording, a constant frequency signal is written in a part of the track recorded by the magnetic head mounted on the rotating drum regardless of the recording mode, and at the time of reproducing. The recording mode is determined by the cycle of the signal. Further, in particular, when the number of drum rotations in the recording mode and the reproduction mode is different, the output video signal is once frozen and then the mode is switched. By canceling the freeze after the mode is changed, it is possible to improve the screen discrimination at the time of mode discrimination and the mode change.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the magnetic recording / reproducing apparatus of the present invention will be described below with reference to FIGS.

FIG. 1 is a diagram best representing the features of the present invention. In FIG. 1, 1 is a compression circuit for compressing an input digital video signal, and 2 is an error correction code so that an error can be corrected during reproduction. , SYNC, and an error correction coding circuit 3 for adding ID convert 3 bits from 8 bits to 10 bits in order to remove the low-frequency component of the digital video signal, and from the 10-bit data, data with a low low-frequency component is reduced. This is a modulation circuit for allocation. Also, 4
Is a recording equalization circuit for recording / equalizing and amplifying, and 5 is an AT for generating four kinds of ATF signals to be recorded on a magnetic tape.
F signal generation circuit, 6 is a signal selection circuit for selecting an ATF signal to be recorded from the input ATF signals, 7, 8
Is a memory capable of writing and reading digital video signals.

Reference numeral 9 is a decompression circuit for decompressing and outputting a compressed digital video signal, 10 is an error correction decoding circuit for correcting digital data by an error correction code, SYNC and ID added to the digital video signal, 1
Reference numeral 1 is a demodulation circuit that performs inverse conversion to the above 8-10 conversion performed on the recording side, 12 is a reproduction equalization circuit that equalizes the waveform reproduced from the magnetic tape, and 13 is an amplifier that amplifies the waveform reproduced from the magnetic tape. It is a head amplifier.

Reference numeral 14 is a low-pass filter (LP) for extracting only the pilot signal from the ATF signal.
F), 15 is a pilot signal envelope detecting circuit for detecting the envelope of the pilot signal, 16 is an ATF error calculating circuit for calculating an ATF error based on this envelope signal, and 17 is a synchronizing signal detecting circuit for detecting a synchronizing signal from the reproduced signal. . 18 is ATF from the above synchronization signal
A timing generation circuit that determines the timing of sample hold with respect to the envelope of the pilot signal of the error calculation circuit 16, 19 is a servo circuit that controls the rotating drum and capstan using an ATF error or the like, and 20 is a synchronization signal detection and drum , Is a microcomputer that switches the playback mode from the servo lock of the capstan.

Further, 21 is an A / D converter for converting an analog video signal into a digital signal, and 22 is a D / A converter for converting a digital signal into an analog signal.

The magnetic recording / reproducing apparatus according to this embodiment is constructed as described above, and its operation will be described below. First, at the time of recording, with the mode of the A / D converter 21, compression circuit 1, and error correction coding circuit 2 set on the basis of the selected drum rotation speed, the video signal input from IN is A / D. A / D converted by the converter 21,
It is written in the memory 7 through the compression circuit 1. Then, the signal written on the magnetic tape is switched to the ATF signal or the digital video signal according to the phase of the rotating drum.

When writing the above ATF signal, one ATF signal is selected from the four types of ATF signals output from the ATF signal generation circuit 5 by the signal selection circuit 6 based on the phase of the rotating drum, and recording, etc. It is recorded on the magnetic tape through the digitizing circuit 4. When writing a digital video signal, an error correction code and SYNC, are added to the compressed video data retrieved from the memory 7.
The ID is added by the error correction coding circuit 2. afterwards,
The modulation circuit 3 performs the 8-10 conversion, and the data is written on the magnetic tape through the recording equalization circuit 4.

Here, an example of the track pattern recorded on the magnetic tape as described above is shown in FIG.

On the other hand, at the time of reproduction, the signal reproduced from the magnetic tape is amplified by the head amplifier 13 and input to the reproduction equalization circuit 12, LPF 14 and sync signal detection circuit 17, respectively. The sync signal detection circuit 17 detects sync signals 1 and 2 (see FIG. 2) in the ATF area on the magnetic tape, and detects the sync signals 1 and 2 (see FIG. 2).
Notify 8. In the timing generation circuit 18, AT
Generate the timing required for F error calculation, and set this to A
It is input to the TF error calculation circuit 16. The ATF error calculation circuit 16 samples the envelope of the pilot signal extracted through the LPF 14 and the pilot signal envelope detection circuit 15 at the timing from the timing generation circuit 18, calculates the ATF error by this, and outputs the ATF error to the servo circuit 19. The data is output and the servo circuit 19 controls the rotary drum.

The signal input to the reproduction equalization circuit 12 is reproduced and equalized, and then the demodulation circuit 11 outputs the signal.
It is inverse-converted from the −10 conversion and input to the error correction decoding circuit 10. In the error correction decoding circuit 10, the error correction of the data is performed by the error correction code, and the data is written in the memory 8. The decompression circuit 9 decompresses the video data in the memory 8, and the video data is output through the D / A converter 22. As described above, when the drum rotation number at the time of recording and the drum rotation number at the time of reproduction match, the operation is performed according to the above method.

Further, a case where the number of drum rotations at the time of recording is different from that at the time of reproducing will be described below. Here, FIG. 3 shows a decision table of the operation of the microcomputer 20 in this case. In FIG. 3, the drum rotation speed mode in the “condition” column of this decision table is the microcomputer 2
The drum rotation speed commanded by 0, and the servo lock,
Servo lock for the commanded drum speed,
The synchronization detection is ON when the synchronization signal is detected once or more in one frame. The operations to be performed by the microcomputer 20 under these conditions are shown in the "case" column.

For example, the drum rotation speed during recording is 9000.
rpm and the drum speed during playback is 4500 rpm
In this case, the reproduction signal of the sync signal of the ATF area on the magnetic tape has a frequency that is 1/2 of that in the case of recording. Then, the synchronization detection OFF is input to the microcomputer 20. At this time, if the rotary drum rotates at 4500 rpm and the servo lock from the servo circuit 19 to the rotary drum is ON, the microcomputer 20 causes the error correction decoding circuit 1 to operate.
For 0, data writing to the memory 8 is prohibited and the output image of the OUT terminal of the image signal is frozen. The microcomputer 20 sets the drum rotation speed mode to 9000 rpm.
Change to.

When the drum rotation speed mode is 9000 rpm, the drum servo lock signal from the servo circuit 19 is ON, and the synchronization detection is ON,
The write-protection to the memory 8 for the error correction decoding circuit 10 is released, and thereby the output image of the OUT terminal is switched from the freeze to the reproduced image. Even when the drum rotation speed during recording is 4500 rpm and the drum rotation speed during reproduction is 9000 rpm, the same operation as above is performed according to the decision table shown in FIG.

As described above, according to this embodiment, when the drum rotation speeds in the recording mode and the reproducing mode are different, the output video signal is once frozen and then the mode is switched. By canceling the freeze after the mode is changed, it is possible to improve the screen discrimination at the time of mode discrimination and the mode change. Therefore, it is possible to obtain an effect that a failed image is not output at the time of mode transition. It should be noted that in the above-described embodiment, the example in which the image is frozen at the time of mode transition has been described, but it is also possible to output a preset image such as a blue background.

Next, a second embodiment of the magnetic recording / reproducing apparatus of the present invention will be described. By the way, as described above, in the conventional magnetic recording / reproducing apparatus, the CTL signal written in the longitudinal direction of the magnetic tape at a constant period at the time of recording is measured at the period at the time of reproducing, the mode is determined, and the reproducing mode is set. I am trying to switch. Therefore, there is a drawback that the data written on the magnetic tape at the mode switching portion cannot be read until the mode is changed.

Therefore, according to the second embodiment, when the recording mode written on the magnetic tape at the time of recording is different from the recording mode to be recorded, the recording is started at the recording start position on the magnetic tape. In the recording mode to be recorded, after recording the fixed pattern data for a certain period of time, by recording the video signal that the user intends to record, the video signal recorded by the user at the time of reproduction is changed to the data accompanying the switching of the recording mode. It is intended to protect from the lack of.

Here, in the magnetic recording / reproducing apparatus according to the second embodiment, referring to FIG. 1, a panel 23 configured to appropriately display an alarm and to be operated by a user is connected to the microcomputer 20. It is supposed to be done. The basic configuration of the device according to the second embodiment is similar to that of the first embodiment.

In the second embodiment, when the recording mode written on the magnetic tape coincides with the recording mode to be recorded from now on, the drum rotation speed during recording and the reproducing time already described in the first embodiment are described. Basically, it operates in the same way as when the drum rotation speeds match.

Particularly in the second embodiment, when the recording mode written on the magnetic tape and the recording mode to be recorded do not match, the operation is performed according to the flow chart shown in FIG. The detection of the recorded mode is performed by using the sync signals 1 and 2 of the track pattern shown in FIG. For example, if the drum rotation speed during recording is 9000 rpm and the drum rotation speed during playback is 4500 rpm, A on the magnetic tape
The reproduction signal of the synchronization signal in the TF area has a frequency half that of the recording, and the synchronization signal detection circuit 17 does not detect the synchronization detection. At this time, synchronization detection OFF is input from the synchronization signal detection circuit 17 to the microcomputer 20. Similarly, when the drum rotation speed during recording is 4500 rpm and the drum rotation speed during reproduction is 9000 rpm, the synchronization detection OFF is input to the microcomputer 20. Synchronous detection ON is input to the microcomputer 20 only when the number of rotations of the drum during recording matches the number of rotations of the drum during reproduction.

By detecting a sync signal in the sync signal detection circuit 17 from the reproduced signal from the head amplifier 13, the recording mode written on the magnetic tape is determined. Then, when the recording mode to be recorded is not in agreement with the recording mode on the magnetic tape in response to the signal from the synchronization signal detection circuit 17, the microcomputer 20 outputs an alarm to the panel 23 as shown in FIG. To display.

Then, while the alarm is displayed on the panel 23, a fixed pattern recording command is input from the panel 23 to the microcomputer 20 by an operation by the user (operator). Then, the microcomputer 20 prohibits writing from the compression circuit 1 to the memory 7, newly writes the blue back fixed pattern in the memory 7, and sets the fixed period for the mode transition on the magnetic tape by the recording method described above. Recording is performed in the specified recording mode.

After that, the tape is rewound by the tape feed amount required from the stopped state to the start of recording, stopped, and a recording command from the operator is waited. In response to a recording command from the operator, the microcomputer 20 starts tape feeding and records a video signal from the end point of the fixed pattern (blue back) according to the recording method described above.

As described above, according to the second embodiment, particularly when the recording mode already written on the magnetic tape and the recording mode to be recorded are different, the recording mode to be recorded is By recording the required video signal after recording the fixed pattern for a certain period of time, it is possible to protect the required video signal from data loss even during the mode transition accompanying the switching of the recording mode during reproduction.

In the second embodiment, since the fixed pattern recording operation independent of the video signal recording operation is prepared, this fixed pattern can be used as a search point at the time of cueing.

[0034]

As described above, according to the present invention, a signal recorded at a constant frequency at the time of recording is detected at the period of the signal at the time of reproduction, and the mode is detected. Even if the recording mode is switched only by the drum rotation number and the tape feeding speed is constant, the recording mode can be detected during reproduction. In addition, even when the playback mode and the recording mode are different, the signal period can be measured, the detection time is short, and even if the VTR is in STOP mode and the tape is stopped,
It can be detected if the rotating drum is rotating. In addition, recording mode and playback mode are different, and when switching the mode during playback, by switching the output video signal to freeze or blue back, it is possible to effectively prevent screen disturbance during mode transition. Have

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a magnetic recording / reproducing apparatus according to the present invention.

FIG. 2 is a diagram showing a track pattern on a magnetic tape according to the present invention.

FIG. 3 is a diagram showing a mutual relationship between a “condition” and a “case” in the microcomputer according to the present invention.

FIG. 4 is a flowchart showing the operation of the microcomputer in the second embodiment of the magnetic recording / reproducing apparatus according to the present invention.

FIG. 5 is a block diagram showing a configuration example of a conventional magnetic recording / reproducing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 compression circuit 2 error correction coding circuit 3 modulation circuit 4 recording equalization circuit 5 ATF signal generation circuit 6 signal selection circuit 7, 8 memory 9 expansion circuit 10 error correction decoding circuit 11 demodulation circuit 12 reproduction equalization circuit 13 head amplifier 14 LPF 15 Pilot signal envelope detection circuit 16 ATF error calculation circuit 17 Synchronization signal detection circuit 18 Timing generation circuit 19 Servo circuit 20 Microcomputer 21 A / D converter 22 D / A converter 23 Panel

Claims (2)

[Claims] 1. A helical scan type magnetic recording / reproducing apparatus having two or more kinds of recording modes in which the rotating speed of a rotating drum is different, wherein a constant amount is applied to a part of a magnetic tape by a rotating head on the rotating drum during recording. Write a frequency signal and detect the frequency of the written signal during playback to determine the recording mode.If the recording mode and playback mode are different, the freeze mode or fixed pattern image is output at the same time when the mode is switched. The magnetic recording / reproducing apparatus is characterized in that when the mode transition is completed, the reproduced video signal of the magnetic tape is output again. 2. In a helical scan type magnetic recording / reproducing apparatus having two or more types of recording modes in which the rotational speed of a rotary drum is different, a recording mode previously written on a magnetic tape and a recording to be recorded from now on. A magnetic recording / reproducing apparatus characterized in that, when the mode is different, a fixed pattern is recorded in a recording mode to be recorded for a certain period from a recording start position, and then a video signal is recorded.