JPS6116074A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To check whether the drop-out can be corrected or not by outputting a drop-out detecting signal when a drop-out signal exceeding the limit of the error correcting capacity is produced after calculating said capacity limit. CONSTITUTION:The drop-out of the digital reproduction signals to which the error correction codes distributed to each track are added is detected by drop- out detectors 3-11 provided to each track. These detection outputs are calculated by an arithmetic part 13 through the gate processing, etc. Then the drop-out detection outputs are produced through terminals 14 and 15 of the part 13 in case the outputs of two of detectors 3-11 last longer than the prescribed time of the limit of the error correcting capability and in case all detection outputs last longer than another prescribed time of the limit respectively. In such constitution, it is possible to check whether the drop-out can be corrected or not. Thus, the state of deterioration due to the drop-out is clear for a reproduction signal.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a magnetic recording/reproducing device that converts a desired signal into a digital signal, adds an error correction code, and records the signal digitally, and particularly relates to a magnetic recording/reproducing device that converts a desired signal into a digital signal and records the digital signal by adding an error correction code. The present invention relates to a magnetic recording/reproducing apparatus having a function of warning of deterioration of a reproduced signal when a dropout exceeding the limit of correction ability occurs.

[Prior Art] Conventionally, there has been a dropout detection device for this type of magnetic recording/reproducing apparatus as shown in FIG. 1.6 FIG. 1 is a schematic diagram of a dropout detection device for five tracks. In the figure, (1) is the reproduction magnetic head of track l, (2 is the amplifier that amplifies the reproduction signal of the reproduction magnetic head (1), and (3) is the reproduction signal of the reproduction magnetic head (page l). This is a dropout detector that detects dropouts caused by Track (2) or track (
5) is also the same as the structure of the track (1), so a detailed explanation thereof will be omitted.

Next, the operation of the above configuration will be explained.

The dropout detection operation is the same for both tracks (1) to (5), so below:
An example of track (1) will be explained.

FIG. 2 shows output waveforms at various parts of the dropout detection device.

The reproduction signal of the reproduction magnetic head (+') is amplified by the amplifier (2) to a desired signal amplitude value shown in FIG. 2(a).

The amplitude value of the reproduction signal from the reproduction magnetic head (1) is:
Unevenness may occur due to non-uniformity of the magnetic surface of the recording medium (not shown), clogging in the gap of the reproducing magnetic head (1), or instability of the contact state between the reproducing magnetic head (1) and the recording medium. This results in a stable amplitude value.

This deterioration in the amplitude value of the reproduced signal is detected by a dropout detector (3), which generates an output signal consisting of a pulse signal as shown in FIG. 2(b). The generation of the output signal from the dropout detector (3) indicates that accurate signal processing is not being performed on the reproduction signal from the reproduction magnetic head (1).

However, the conventional dropout detection device described above is limited to the function of detecting dropouts in each track, and the playback signal itself is affected by the occurrence of dropouts.
There was a drawback that it was not possible to detect the degree of signal deterioration.

[Summary of the invention] This invention was made to solve the above-mentioned drawbacks.
Regarding random or burst dropouts that occur during the recording and playback process of a recorded signal to which an error correction code has been added, it is possible to determine whether or not the playback signal is a correctable dropout by calculating the limit of the error correction ability using a calculation means. An object of the present invention is to provide a magnetic recording/reproducing device capable of detecting.

[Embodiments of the invention] Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 3, (13) is an arithmetic unit, and this arithmetic unit (1
3) reads dropout signals corresponding to 5 tracks (1) to (5) from dropout detectors (3), (?), and (11), and detects each dropout signal of 5 tracks in 42. When the dropout signals of two tracks selected from the out signals are generated for a period of time t1 or more, the output terminal (14) which generates an output signal and all the dropout signals of the five tracks mentioned above are generated for a period of time t2 or more. and an output terminal (15) that generates an output signal when

FIG. 4 is a time chart of output signals in each component in FIG.
) The time chart of the dropout signal is omitted.

Next, the operation of the above configuration will be explained.

As mentioned above, after converting a desired signal into a digital signal, when transmitting the signal using an electric-magnetic conversion system, that is, a transmission system based on magnetic recording and reproduction, the magnetic spatula l'' (1
) and recording media, there is a problem that dropouts occur in the reproduced signal. As a countermeasure against this, interleaving is used to disperse the digital signal on the time axis, and means for adding an error correction code is used.

However, although the ability of these means to prevent deterioration of reproduced signals varies depending on the means, there is a limit to their ability. This correction ability can be expressed as how many tracks must have no playback signal to be corrected, and if playback signals cannot be obtained from all tracks at the same time, within how many seconds can correction be turned off? It is expressed in terms of strength such as.

Regarding the correction ability described in this example, if a dropout signal occurs simultaneously over two tracks,
If the generation time is less than, for example, 11 seconds, correction is possible, and if the dropout signal occurs simultaneously across all tracks, if the generation time is less than, for example, t2 seconds, correction is possible. Now, dropout detectors (3) for tracks 1.2 and 5, respectively.
), (?), and (+1) are shown in FIGS. 4(a) to h).

First, one limitation of the error correction capability of the arithmetic unit (13) will be explained. For the dropout signals of tracks 1 and 2.5 shown in FIG. 4(fL) to C), create the combinations of each two tracks shown in FIG. 4(d) to f), and perform AND on each. After detecting the output, the time period during which each AND output signal continues to occur is counted, and as shown in FIG.
An output signal is generated from the output terminal (14) of.

Next, another example of the error correction ability in the arithmetic unit (13)
To explain one limitation, all tracks 1 and 2
．． AND the dropout signal from 5, count the time that this AND output signal continues to occur,
As shown in FIG. 4(h), A
When an ND output signal is generated, the detection output signal is generated from the output terminal (15) of the calculation section (13).

When output signals are generated from the above output terminals (14) and (15), each output signal indicates a different state of dropout, but all signals mean that the error correction capability has been exceeded. Therefore, compensation means such as previous value correction and average value correction are used for the reproduced signal, and a signal different from the original signal is substituted.

In the above embodiment, a case has been described in which the calculation unit (13) calculates the limit of error correction ability for two items, but the calculation unit (13) also includes a detection means for detecting a new item other than the above, It may be provided with an output terminal corresponding to the limit [1, and furthermore, this calculation section (13) may be constituted by a microcomputer that performs calculation and counting functions.

Furthermore, even if the number of tracks is other than the above, by setting the error capacity limit item in the calculation unit (13) in the specific error correction means corresponding to the number of tracks,
The same effects as in the above embodiment are achieved.

Further, in the above embodiment, the case where the dropout detectors (3), (7), and (11) are provided for each track has been described;
), (7), and (11) can be shared between each track by time-division processing to detect a dropout signal, and the same effect as in the above embodiment can be obtained.

In the above embodiment, the operation of detecting whether or not the dropout exceeds the error correction capability was explained based on the dropout signal in the arithmetic unit (13). As shown in each output terminal (14)
, deciles that count the output signals of (15), ;I
Counting devices (16) such as a-meters (16a) and (18b)
and a display device (17) consisting of respective indicators (1?a) and (+7b) for the counted values, or a light emitting device (17) consisting of light emitters (+8a) and (18b) as shown in Fig. 6. By providing the display device (18), it is possible to know more specifically the frequency of occurrence of the detection output signal.

That is, in FIG. 5, the number of occurrences of the detection output signal of the arithmetic unit (13) is counted by the counting device (18), and the counted value can be displayed on the display device (17). In addition, in FIG.
When a detection output signal is generated, a light-emitting display device W such as a lamp
(18) to emit light, and this light emitting display device (
18) is recommended to be designed so that the luminescence time can be visually detected.

■As shown in -, based on the detection output signal, count table / ] <
The quality status of the reproduced signal can be known more specifically by the count display by the device (17) and the light emission by the light emitting display device (18).

Also, in the error correction section, the quality of the reproduced signal can be determined by the presence or absence of the flag using the error detection code.
When a long-term dropout occurs due to a clogged magnetic head, etc., the number of flags generated is extremely large, and it is very difficult to count the number of flags generated. The number of occurrences can be easily counted.

[Effects of the Invention] As described in 2 below, according to the present invention, there is provided a means for detecting dropouts of a plurality of tracks and outputting a dropout signal, and a means for receiving the dropout signal to overcome the limit of the error correction ability. arithmetic means having an arithmetic function to perform an arithmetic operation, and the arithmetic means is configured to generate a dropout detection output signal when the above-mentioned tropout signal is generated beyond the limit of error correction capability; The function is not limited to detecting dropouts in each track as in the past, but also detects how much signal degradation has occurred due to the occurrence of dropouts in the playback signal itself, and whether or not the playback signal is a correctable dropout. It has the advantage of being able to

In addition, for recorded signals with error correction codes added, we can also test whether dropouts that occur during the recording and playback process are random or eight-stroke, or whether they are due to long-term dropouts due to clogging of the magnetic head. 'There is an effect that can be produced.

[Brief explanation of the drawing]

Fig. 1 is a schematic block circuit diagram of a dropout detection device in a conventional magnetic recording/reproducing device, Fig. 2(a),
(b) is a time chart of output signals in the circuit section of FIG. 1, FIG. 3 is a schematic block circuit diagram of a dropout detection device in a magnetic recording/reproducing device according to the present invention, and FIG. h) is a time chart of output signals in the circuit section of FIG. 3, FIG. 5 is a schematic block circuit diagram showing an example of a count display device in a magnetic recording/reproducing apparatus according to another embodiment of the present invention, and FIG. FIG. 2 is a schematic block circuit diagram showing an example of a light emitting display device in a magnetic recording/reproducing device according to still another embodiment of the present invention. (3), (7), (I I)...Trombout detector, (13)...Calculating unit, (16)...Counting device, (17)...Counting display device, (18)... )...Light-emitting display device. In addition, the same reference numerals in Figure 1 indicate the same or equivalent parts.

Claims (5)

[Claims] (1) In a magnetic recording/reproducing device configured to convert a desired signal into a digital signal and add an error correction code, and then distribute the digital signal to a plurality of tracks, dropout of the plurality of tracks is detected. means for outputting a dropout signal, and a calculation means having a calculation function for calculating the limit of the error correction capability in response to the dropout signal, and the calculation means is configured to output a dropout signal when the dropout signal is corrected. A magnetic recording/reproducing device characterized in that it is configured to generate a dropout detection output signal when a dropout occurs beyond a capability limit. (2) The calculation means is configured to generate a dropout detection output signal when a predetermined number of dropout signals selected from dropouts of a plurality of tracks occur for a preset detection time or longer. A magnetic recording and reproducing apparatus according to claim (1). (3) The above-mentioned calculation means is configured to set a plurality of dropout detection tracks and a plurality of detection times, and generate a dropout detection output signal corresponding to each combination. No. (
2) The magnetic recording and reproducing device described in item 2). (4) Claims (1) to (1) comprising counting means for counting the number of dropout detection output signals generated from the calculation means, and counting display means for displaying the counted value. The magnetic recording and reproducing device according to any one of paragraph (3). (5) Claims according to any one of claims (1) to (3), comprising a light-emitting display means for displaying the number of dropout detection output signals generated from the calculation means by light-emitting light. magnetic recording and reproducing device.