JPS62203494A - Drop out correction system for recording medium - Google Patents

Abstract

PURPOSE:To replace with a completely corrected normal signal at a drop out generating point at the time of reading a recording signal and to output it by storing the time code data of a position where the drop out has occurred and the normal recording signal to the first and the second memories. CONSTITUTION:The first memory means 18 for storing the time code corresponding to the drop out position of a recording medium as the data and the second memory means 19 for storing the signal recorded in the drop out point are provided. At every time when the time code recorded in the recording medium coincides with the time code data recorded in the first memory means 18, the signal is read from the second memory means 19. Thereby, at the point having the drop out, a video signal stored in the memory or the like is outputted to perform the complete drop out correction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for effectively correcting signal loss caused by dropouts of tapes, disks, etc.

[Summary of the invention]

The dropout correction method of the present invention records an if memory for recording a time code when a dropout is detected, and recording information corresponding to a time code position that matches data in this first memory. A second memory is provided, and when the time code matches that of the first memory, recorded information is read from the memory of JrI2 and output in place of the reproduction signal.

[Conventional technology]

When recording signals on a magnetic tape or the like, increasing the Q density inevitably narrows the recording track width, and even small scratches in the magnetic layer can cause signal loss. Therefore, it is difficult to avoid dropouts that occur in high-density recording.

Therefore, for example, in video IQ recording and reproducing apparatuses, a dropout correction circuit is usually used that uses an IH delay circuit to supplement the video signal before LH when a dropout is detected.

[Problem that the invention seeks to solve]

In this case, since the video signal has line correlation in the vertical direction, the effect of dropout correction can be seen considerably, but strictly speaking, the video signal is a different signal for each IH, so a particularly high resolution is required. This can be a problem for broadcast stations and data screen signals.

The present invention has been made in view of these problems.
The purpose of this invention is to provide a dropout correction method that completely corrects dropouts by outputting a video signal stored in a memory or the like.

[Means for Solving the Problems] The present invention provides a first memory means that stores a time code corresponding to a dropout point of a recording medium as data, and a first memory means that stores a signal recorded at the dropout point. a second memory means, and a signal is read from the second memory means each time the time code recorded on the recording medium and the time code data recorded on the first memory means match. Configure it as follows.

[Effect]

A time code corresponding to a missing portion on the recording surface of the recording medium is recorded in the first memory means in advance or during playback, and a recording signal input at that point is stored in the second memory means. Therefore, when a dropout point is encountered during playback, a normal signal before being dropped out is output from the second memory means, making it possible to avoid dropout.

〔Example〕

1(a) and (b) are block diagrams of an embodiment in which the dropout correction method of the present invention is applied to a magnetic tape recording/reproducing method, and 11 is a recording signal processing circuit when recording a video signal; 12 is a rotating head, 13 is an A/D converter,
14 is a digital comparator, 15 is a decoder, 16 is a fixed head that detects the time code, 17 is a switch circuit, 18 is a second memory that can record video signals for 1 field, and 19 is a second memory that can record video signals for 1 field. This is the first memory that stores the time code on the recording surface of the magnetic tape T where the recording surface is missing.

Further, FIG. 1(b) shows a block diagram of a playback mode using the dropout correction method of the present invention.
A) and the same-a clear part are given the same reference numerals. In this figure, 21 is a reproduction signal processing circuit, 22 is a dropout detection circuit, 23 is a D/A converter, 24 is a logic gate, 25 is a switching circuit, 26 is a conventional IH delay dropout compensation circuit, 27 is a gate circuit.

Hereinafter, a dropout correction method will be explained with reference to the above-mentioned block diagram.

In FIG. 1(a), the time code of the video signal (signal indicating the field width) is recorded on the magnetic tape T as described later, and the time code corresponding to the missing part on the magnetic surface of the magnetic tape T is recorded. is stored in the first memory 19.

When a video signal is supplied from the terminal TR to such a magnetic tape T, the video signal for each field is recorded by the rotary head 12, for example, in zone A shown in FIG. And the track TM where the time code is recorded
A signal indicating the progress state of the tape is detected from C by the fixed head 16 and inputted to the digital comparator via the decoder 15.

As described above, the first memory 19 stores the time code data when there is a defective part on the magnetic surface of the magnetic tape T, so the time code output from the decoder 15 during recording and the first When the data stored in the memory match, a missing position detection signal is output from the digital comparator 14, and the switch circuit 17 is closed. Then, the video signal being input at this time is input to the second memory 18 via the A/D converter 13.

In this case, if a control circuit (not shown) outputs a time code that is one track earlier than the time code of the missing video track, the video signal recorded on the missing track of the magnetic tape T, for example, , l fields can be recorded in the second memory 18 for one minute.

Thereafter, in this way, every time a missing track is encountered, the video signal for one field is stored in the second memory.

When the predetermined recording is completed, the data stored in the first and second memories are transferred to the leading portion DS of the magnetic tape T, for example, as shown in FIG. By recording this information together, the 1: dropout correction IF can be performed on other magnetic tapes as well.

When the magnetic tape T on which the dropout correction information is recorded in this way is played back, the dropout correction information is first recorded in the first . The data is read into the second memory 18-19.

The data is then reproduced in blocks as shown in FIG. 1(b).

That is, the video recording signal in the A zone of the magnetic tape T is read out by the rotary disc 12 while being read out by the playback signal processing circuit 21 and the switch circuit 2 normally located at the solid line position.
5 to the dropout compensation circuit 26, and is reproduced as a video signal from the terminal Tp. When a dropout that was not detected during recording is detected by the dropout detection circuit 22, it is corrected by a conventional draw/dropout compensation circuit 26 via a logic gate 24.

However, the data stored in the first memory 19 and
When the time codes detected by the fixed head 16 match and, for example, a signal indicating a video track with a dropout is output from the digital comparator 14,
The switch circuit 25 is switched to the dotted line position, and the previously written normal video signal is read out from the second memory 18 in response to a timing signal (not shown), and is output as a replacement for the reproduction signal.

That is, when the time code To indicating the dropout point is encountered in FIG. 2, the unrecorded video signal stored in the second memory 18 is output instead of the +Jg raw signal of the next video track. , which completely corrects dropout.

Therefore, when the dropout correction method for the recording medium of the present invention is adopted, dropouts that suddenly occur during playback can be avoided by the conventional dropout compensation circuit 26.
Since the dropouts detected in advance are completely corrected, dropouts can be corrected with extremely low redundancy.

Furthermore, if the gate circuit 27 is opened by the signal detected from the dropout detection circuit 22 during playback as shown by the dashed line in FIG. 1(b), the time code of the magnetic tape T at this time becomes the first Since it becomes possible to record additionally to the memory 19, the newly discovered dropout point will be sent to the predetermined address of the second memory at the next recording time, as shown in FIG. 1(a). - You will be able to memorize the same and be able to perform complete dropout correction.

At this time, it is necessary to record (1) data indicating new dropout information at the beginning of the magnetic tape T.

If the recording medium is a magnetic tape, as mentioned above, the data is placed in the area DS at the beginning of the magnetic tape.

I tried to record the dropout information, but the magnetic disk (
In the case of a floppy disk, etc., several tracks (DS) on the inner circumference side of the disk D can be designated as the recording area for dropout information, as shown in FIG.

FIG. 4 shows an operating circuit when inputting dropout information to a tape to which dropout information has not been inputted, for example, a virgin tape Tv, in which 28 is a time code generator and 29 is a dropout detection circuit.

For the virgin tape Tυ, use the fixed helad 16,
First, time code data is recorded, and the rotary head 30 records and reproduces standard signals in monitor mode. When a dropout is detected in the playback output, the switch circuit 31 is closed and the time code generator 2
8 data is recorded in the first memory 19.

Then, the entire recording area of the virgin tape Tv is inspected for dropout locations, and the dropout information is stored in the first memory, and at the same time, after the inspection is completed, the dropout information is written to the leading end of the virgin tape Tυ as described above. be recorded.

Note that defective tapes with more dropout information than a predetermined number may be discarded at this stage.

〔Effect of the invention〕

As explained above, the dropout correction method of the recording medium of the present invention is such that the time code (or frame number) data of the location where the dropout occurred and the normal recording signal are stored in the first and second memories. Since it can be memorized, when reading out the recorded signal, it can be output in place of a normal signal that has been completely corrected at the point where the dropout occurred, enabling dropout correction with low redundancy. It has the effect of becoming

Furthermore, by recording dropout information at the beginning of the target recording medium, there is an advantage that the dropout correction method of the present invention can be repeatedly applied during subsequent reproduction.

[Brief explanation of drawings]

FIGS. 1(a) and (b) are block diagrams of the recording/reproduction system showing the dropout correction method of the recording medium of the present invention, FIG. 2 is an explanatory diagram of the tape format showing dropout information, and FIG. FIG. 4 is a block diagram for detecting dropout. In the figure, 11 is a recording signal processing circuit, 12 is a rotating head, 1
3 is an A/D converter, 14 is a digital comparator, 15
is a decoder, 16 is a fixed head, 18 is a first memory,
19 is a second memory, 21 is a reproduction signal processing circuit, 22 is a dropout detection circuit, 23 is a D/A converter, and 24 is a logic gate.

Claims (2)

[Claims] (1) A first memory that records a time code when a dropout is detected, and a second memory that can record a signal corresponding to the time code recorded in the first memory. , when the time code read from the recording medium and the time code recorded in the first memory match, the signal recorded in the second memory is output in place of the signal being played back. A dropout correction method for recording media characterized by the following. (2) The data stored in the first and second memories is recorded as dropout information in the leading area of the recording medium, and the dropout information is recorded in the first and second memories during playback. A dropout correction method for a recording medium according to claim (1), characterized in that: