JPS6271062A - Magnetic tape recording and reproducing device - Google Patents

Abstract

PURPOSE:To always make proper reproduction of recorded information as far as a reproducing system is normal, by installing a switch for switching a recording alarm level signal and reproducing alarm level signal to each other to an error rate alarm detecting circuit. CONSTITUTION:The error detecting signal of a channel A or B is inputted to an input terminal 35 and the number of error detecting times in a fixed period is counted by an error counter. The counted value is held by a latch section 37 until the next calculation. The value is compared with a recording alarm level signal outputted from a recording alarm level signal generating section 40 at the time of recording, and with a reproducing alarm level signal outputted from a reproducing alarm level signal generating section 41 at the time of reproduction in level by means of a comparator 38 through a switch 39. The value of the recording alarm level signal from the section 40 is set smaller than the value of the reproducing alarm level signal of the section 41.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a digital recording type magnetic tape recording and reproducing device, and in particular to error rate alarm detection for a magnetic tape recording and reproducing device that performs high-density recording such as a digital VTR. It is related to circuits.

[Conventional technology]

The alarm detection value of the conventional error rate alarm detection circuit was a constant value without distinguishing between recording and reproduction.

[Problem that the invention seeks to solve]

However, in the digital VTR having the above-mentioned conventional error rate alarm detection circuit, even if the error rate is lower than the alarm detection level during recording and no alarm is generated, during playback the error rate may be lower than the alarm detection level, but during playback An alarm could occur due to a deterioration of the error rate due to changes in characteristics or compatible playback. In this case, it may be necessary to re-record after a considerable period of time (several days to half a year) has passed, which is inconvenient.The above problem can be solved by lowering the alarm detection value, but the reproduced image An error rate alarm will occur within a range that is sufficient to withstand use, and digital V
In TR, the range of use is narrowed and this is not preferable.

c. Means for Solving Problems] In order to solve these problems, the present invention provides a recording alarm level signal generating section that generates a recording alarm level signal, and a reproduction alarm level signal generating section that generates a reproduction alarm level signal. The error rate alarm detection circuit is provided with a generator and a switch for switching between the recording alarm level signal and the reproduction alarm level signal.

[Effect]

In the present invention, the error rate alarm detection value is switched to different values during recording and reproduction, and the detection value during recording is made lower than the detection value during reproduction. As a result, recorded information is always reproduced correctly as long as the reproduction system is normal.

[Embodiment] An embodiment of the magnetic tape recording/reproducing device according to the present invention is shown in FIG. 1, FIG. 2 is a layout diagram showing the position of the head in the drum section 30, and FIG. 3 is a configuration of the device. FIG. 3 is a circuit diagram showing an error rate alarm detection circuit.

Figure 1(a) shows the recording system of this device, and 1 indicates NTSC.
An input terminal to which an analog video signal is input; 2 is an A/D converter that is sampled at a frequency four times that of the subcarrier and has a quantization number of 8 bits; 3 is a drum unit 30 shown in FIG.
A time axis compression section that delays the compression by 2 hours so that the input signal is recorded according to the tape format specified in the magnetic tape winding effective section of the magnetic tape. 4 is necessary for correctly restoring the playback signal from the magnetic tape. 2 Adding synchronization signals, address signals, error detection codes, error correction codes, etc.
5 is an M-sequence signal generating section; 6 is a scrambler for digital signals outputted from the adding section 4 and M-sequence signal generating section 5 to undergo addition modulo 2, that is, to be scrambled; , 7 is a parallel-to-serial converter for parallel-to-serial converting the scrambled signal, 8 is a recording amplifier for amplifying this signal, 9 is a rotating transformer, 1
0A and IOB are recording heads for recording signals on tape. This device uses scrambled NRZ as a channel code.

Next, the regeneration system shown in Fig. 1 will be explained.

The signals recorded on the tape are transmitted to the playback head 11A,
11B, and is amplified with low noise by a regenerative amplifier 12 mounted on the drum section shown in FIG. This reproduced and equalized signal is subjected to serial-to-parallel conversion in a serial-to-parallel converter 16 using the clock and synchronization signal output from the clock recovery synchronization signal detection section 15. Next, the time axis correction unit 17 removes the time axis variation included in the reproduced signal.The 0M sequence signal generation unit 18 is the same as the M sequence signal generation unit 5 in the recording system, and the output signal of the M sequence signal generation unit 1 day is the same as the M sequence signal generation unit 5 in the recording system. A descrambler 19 performs addition modulo 2 of and the output signal of the time axis correction section 17 using a descrampler 19.
The output signal of is descrambled, and the pre-scrambled signal is demodulated.

Next, an error detection section 20 detects an error in the data using an error detection code added to the reproduced signal.

In the error correction unit 21, error data within a theoretically correctable range is corrected using the error signal output from the error detection unit 20 and the error correction code included in the reproduced signal.
The correct original signal will be reproduced. In the error correction section 21, most of the error data included in the reproduced signal is corrected and reproduced as a correct original signal, but if dropouts occur abnormally frequently, error data that cannot be corrected remains. These residual error data are processed in the next error correction section 22.
Replaced with the signal before the line. As a result, image quality deterioration due to error data is hardly visually noticeable. The signal is time-axis expanded by a time-axis expansion unit 23, and then demodulated into an analog video signal by a D/A conversion unit 24.
It is output from the output terminal 25. Another output signal of the error/detection section 20 is the error rate alarm detection circuit 2.
6 is input. The subsequent operations will be explained later with reference to FIG.

FIG. 2 shows the drum section 30 of this device. The outer diameter of this drum part is 134.62 mmφ, and the drum rotation direction is 31 mm.
It rotates at 119.88 rps in the direction of . In FIG. 2, IOA and IOB are recording heads, 11A and 11B are reproducing heads, 32 is an erasing head, and 33 is a magnetic tape. With respect to the recording head 10A, the erasing head 32 is advanced by 30 degrees, and the reproducing head IIA is positioned behind by 180 degrees, so that even during recording, simultaneous reproduction can be performed using the reproducing heads IIA and IIB, and reproduction can be monitored. The magnetic tape 33 is
During recording and playback, 241.3 mm in the running direction 34, /
Run in seconds.

Next, according to FIG. 3, the error rate alarm detection circuit 26
I will explain about it. The error detection signal of channel A or B is input to the input terminal 35, and the error counter counts the number of errors detected within a certain period (0.1 seconds in this embodiment). Retained until the next calculation. This value (digital amount) is determined by a comparator 38 through a switch 39, and is output as a recording alarm level signal outputted from a recording alarm level signal generation section 40 during recording, and outputted from a reproduction alarm level signal generation section 41 during reproduction. The level is compared with the reproduced alarm level signal. Count value a of the number of error detections input to the comparator 38
When the relationship a≧b exists between the level b of the alarm signal and the level b of the alarm signal, an alarm signal is output from the output terminal 28.

In this case, in addition to outputting an alarm signal to the host system, the LED 27 on the operation panel of the VTR indicates that the ear alarm is present.

On the other hand, the output a of the touch section 37 is logarithmically converted by the logarithmic converter 42, and then converted into an analog value by the D/A converter 43, and the error rate is displayed on the meter 29. This fluctuation of the meter 29 not only informs the moment-by-moment error rate, but also the in! of the vase 14 such as current recording and playback. ! 11.

Here, the recording alarm level signal outputted from the recording alarm level signal generation section 1 40 is set to a smaller value than the reproduction alarm level signal outputted from the reproduction alarm level signal generation section 41. In this example, the ratio of these signals is chosen to be 1:3.

By making the alarm level signal during recording smaller than the alarm level signal during reproduction in this manner, it is possible to guarantee that recorded information is always reproduced correctly as long as the reproduction system is normal. If the difference in alarm detection values due to the difference in alarm level signals during recording and playback is reduced, the above guarantee effect will be small (and if it is too large,
Although the guarantee effect is greater, the frequency of alarms occurring during recording increases, which is inconvenient for devices such as digital VTRs that do not have a margin for error rate tolerance. In this example, 1:3 was selected, but 1:2 to 1:5 was rarely found within the practically acceptable range.

2. Effects of the Invention] As explained above, the present invention has a recording alarm level signal generation section that generates a recording alarm level signal, a reproduction alarm level signal generation section that generates a reproduction alarm level signal, and a recording alarm level signal generation section that generates a reproduction alarm level signal. By providing the error rate alarm detection circuit with a switch for switching between the alarm level signal and the alarm level signal, it is possible to switch the error rate alarm detection value to different values during recording and playback. By setting the value lower than the detected value during reproduction, it is possible to ensure that the ζ recorded information is always reproduced correctly as long as the reproduction system is normal.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an embodiment of the magnetic tape recording/reproducing device according to the present invention, Fig. 2 is a layout diagram showing the position of the head of the drum section constituting this device, and Fig. 3 is a system diagram showing the position of the head of the drum section constituting this device. FIG. 2 is a system diagram showing an error rate alarm detection circuit constituting the circuit. l, 35...input terminal, 2...A/D conversion section,
3... Time axis compression part, 4... Addition part, 5.18
...M-series signal generator, 6...scrambler,
7... Parallel-serial conversion section, 8... Recording amplification section, 9.
... Rotating transformer, 10A, 10B... Recording head, IIA, IIB... Playback head, 12...
Regenerative amplification section, 13... Rotating transformer, 14...
Regeneration equalizer, 15... Clock recovery synchronization signal detection section, 16... Serial-to-parallel conversion section, 17... Time axis correction section, 19... Descrambler, 20...
Error detection unit, 21... Detection correction unit, 22...
Error correction section, 23... Time axis extension section, 24.43
...D/A conversion unit, 25.2EI...output terminal, 26...error rate alarm detection circuit, 27.
... LED, 29 ... Meter 1.30 ... Drum part, 32 ... Erasing head, 33 ... Magnetic tape, 36 ... Error counter, a7 ... Launch section, 38...Comparator, 39...Switcher, 40
...Recording alarm level signal generation section, 41...
Reproduction alarm level signal generation section, 42...logarithmic conversion section.

Claims (2)

[Claims] (1) A recording alarm level signal generation section that generates a recording alarm level signal, a reproduction alarm level signal generation section that generates a reproduction alarm level signal, and a switch for switching between the recording alarm level signal and the reproduction alarm level signal. and an error rate alarm detection circuit,
A magnetic tape recording/reproducing device characterized in that an error rate alarm detection value is set to be different during recording and during playback. (2) The magnetic tape recording/reproduction according to claim 1, wherein the alarm detection value of the error rate has a ratio between 1/2 and 1/5 during recording and during reproduction. Device.