JPH06101837B2 - Recording medium drop-out correction method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a system for effectively correcting a loss of a signal caused by a dropout of a tape, a disk, or the like.

[Outline of Invention]

According to the dropout correction method of the present invention, a first memory that records a time code when a dropout is detected and recording information corresponding to a time code position that matches the data of the first memory are recorded. A second memory provided, and when the time code matches the first memory, the record information is read from the second memory,
The output is made instead of the reproduction signal.

[Prior Art] When recording a signal with a magnetic tape or the like, if the recording density is increased, the recording track width is inevitably narrowed, and even a small scratch on the magnetic layer causes a loss of the signal. Therefore, it is difficult to avoid some dropout in high density recording.

Therefore, for example, in a video signal recording / reproducing apparatus, normally,
When a dropout is detected using the 1H delay circuit, a dropout correction circuit that replenishes the video signal 1H before is commonly used.

[Problems to be solved by the invention]

In this case, in the case of the video signal, there is a line correlation in the vertical direction, so the effect of dropout correction is considerably recognized, but strictly speaking, the video signal is a signal that differs for each 1H,
This may be a problem particularly in the case of a broadcasting station that requires high resolution or a data screen signal.

The present invention has been made in view of such problems,
In terms of dropout, the purpose is to provide a dropout correction method in which a video signal stored in a memory or the like is output to perform complete dropout correction.

[Means for solving problems]

The present invention comprises a first memory means for storing, as data, a time code corresponding to a dropout point on a recording medium, and a second memory means for storing a signal recorded at a dropout point. Each time the time code recorded on the medium and the time code data recorded on the first memory means match, a signal is read from the second memory means.

[Action]

The time code corresponding to the defective portion on the recording surface of the recording medium is recorded in the first memory means in advance or during reproduction, and the recording signal input at that time is stored in the second memory means. Therefore, when the dropout point is encountered during reproduction, the normal signal before the dropout is output from the second memory means, and the dropout can be avoided.

〔Example〕

1 (a) and 1 (b) are block diagrams of an embodiment in which the dropout correction method of the present invention is applied to a recording / reproducing method using a magnetic tape, and 11 is a recording signal processing circuit for recording a video signal, 12 is a rotary 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, and 18 is a video signal for one field. A second memory 19, which can be used, is a first memory for storing a time code having a recording surface defect portion of the magnetic tape T as described later.

Further, FIG. 1 (b) shows a block diagram of a reproduction mode according to the dropout correction method of the present invention, and the same functional portions as those in FIG. 1 (a) are designated by 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 for switching, 26 is a conventional 1H delay dropout compensation circuit, 27 Is a gate circuit.

Hereinafter, the dropout correction method will be described with reference to the above block diagram.

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

Supplying video signal to such a magnetic tape T from the terminal T _R, for example, video signals of each field in the A zone shown in FIG. 2 is recorded by the rotary head 12. Then, a signal indicating the progress state of the tape is detected by the fixed head 16 from the track TMC on which the time code is recorded and is input to the digital comparator via the decoder 15.

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

In this case, if the control circuit (not shown) controls the time code of one track before the time code of the defective video track to be output, the video signal recorded on the defective track of the magnetic tape T is, for example, Only one field can be recorded in the second memory 18.

Thereafter, in this manner, every time a defective track is encountered, a video signal for one field is accumulated in the second memory.

When the predetermined recording is completed, the data stored in the first and second memories are recorded together with the start / stop marking signals ST and SM on the head portion DS of the magnetic tape T as shown in FIG. Then, the dropout can be corrected for another magnetic tape next.

When reproducing the magnetic tape T on which the dropout correction information is recorded, the dropout correction information is first read into the first and second memories 18 and 19.

Then, the blocks are reproduced as shown in FIG.

That is, the video recording signal in the zone A of the magnetic tape T is read by the rotary head 12 and is input to the dropout compensation circuit 26 via the reproduction signal processing circuit 21 and the switch circuit 25 normally located at the solid line position. It is played back from the terminal T _P as a video signal. Then, when the dropout which is not detected at the time of recording is detected by the dropout detection circuit 22, it is corrected by the conventional dropout compensation circuit 26 via the logic gate 24.

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

That is, when the time code T _O indicating the dropout point in FIG. 2 is encountered, the pre-recorded video signal stored in the second memory 18 is output instead of the reproduction signal of the next video track. , The one that completely corrects the dropout.

Therefore, when the dropout correction method in the recording medium of the present invention is adopted, the dropout that suddenly occurs during reproduction is corrected by the conventional dropout compensation circuit 26, and the dropout previously detected is completely corrected. Therefore, the dropout with extremely low redundancy can be corrected.

When the gate circuit 27 is opened by the signal detected by the dropout detection circuit 22 during reproduction as shown by the alternate long and short dash line in FIG. 1B, the time code of the magnetic tape T at this time is Since the data can be additionally recorded in the memory 19, as shown in FIG. 1 (a), at the time of the next recording, the dropout point newly found is also recorded at a predetermined address in the second memory. Will be memorized and dropout correction will be possible.

At this time, it is necessary to re-record the data indicating the new dropout information at the head portion of the magnetic tape T.

When the recording medium is a magnetic tape, the dropout information is recorded in the area DS at the beginning of the magnetic tape as described above. However, in the case of a magnetic disk (floppy disk) or the like, it is shown in FIG. As described above, several tracks (DS) on the inner peripheral side of the disc D can be designated as the recording portion of the dropout information.

Figure 4 is shows the operation circuit when the input tapes, for example, the drop-out information to the virgin tape T _V is not input dropout information, 28 time code generator, 29 denotes a drop-out detecting circuit .

For the virgin tape T _V, the fixed head 16 first records the time code data, and the rotary head 30
Records standard signals in monitor mode and outputs them for playback. When the dropout is detected in the reproduction output, the switch circuit 31 is closed and the time code generator 28
Data is recorded in the first memory 19.

Then, the dropout point is inspected for the entire recording area of the virgin tape T _V , and the dropout information is first recorded.
At the same time, the dropout information is recorded on the tip of the virgin tape T _V after the inspection is completed.

A defective tape having more dropout information than the specified number may be discarded at this stage.

〔The invention's effect〕

As described above, according to the dropout correction method of the recording medium of the present invention, the timecode (or frame number may be used) data at the location where the dropout has occurred in the first and second memories and the normal recording signal are recorded. Since it can be stored, when the recorded signal is read, it can be output by replacing it with a normal signal that has been completely corrected at the dropout occurrence point, enabling dropout correction with low redundancy. Has the effect of becoming.

Further, by recording the dropout information at the leading end portion of the target recording medium, there is an advantage that the dropout correction method of the present invention can be repeatedly used even after the subsequent reproduction.

[Brief description of drawings]

1A and 1B are block diagrams of a recording / reproducing system showing a dropout correction system of a recording medium of the present invention, FIG. 2 is an explanatory diagram of a tape format showing dropout information, and FIG. 3 is FIG. 4 is an explanatory diagram of the dropout information for the disc, and FIG. 4 is a block diagram for detecting the dropout. In the figure, 11 is a recording signal processing circuit, 12 is a rotary head, and 13 is A /
D converter, 14 is a digital comparator, 15 is a decoder, 1
6 is a fixed head, 18 is the first memory, 19 is the second memory, 2
1 is a reproduction signal processing circuit, 22 is a dropout detection circuit, 2
3 is a D / A converter, and 24 is a logic gate.

Claims (2)

[Claims] 1. A first memory for recording a time code when a dropout is detected, and a second memory capable of recording 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 instead of the signal being reproduced. A dropout correction method for a recording medium characterized by the above. 2. The data stored in the first and second memories is recorded as dropout information in the head area of the recording medium, and the dropout information is reproduced when the data is reproduced.
The dropout correction system for a recording medium according to claim 1, wherein the dropout correction method is recorded in the second memory.