JPS61972A - Magnetic recording and reproducing system - Google Patents

Abstract

PURPOSE:To reduce the probability of data dropout due to flaws or the like on a tape and to shorten the read time of retrieval data by recording data of plural units plural recording tracks unit by unit in a prescribed order and recording data on other recording tracks in the same manner plural times. CONSTITUTION:Recording tracks T1-Tn in a recording part 10 of data for retrieval of a magnetic tape 1 are divided to, for example, blocks B1-B8, and 16 recording tracks are allocated to every block if there are 16 chapters 1-1-3-4. Data for retrieval of the chapter 1-1 is recorded on the first recording tack T1 in the block B1, and data for retrieval of chapters 1-2, 1-3, 1-4, 2-1, 2-2-3-3, and 3-4 are recored in order on recording tracks T2-T16 successively similarly. In blocks B2-B8, data for retrieval of chapters 1-1-3-4 are recorded successively on individual recording tracks similarly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field 1] The present invention relates to a data recording method for a magnetic recording/reproducing device, and more particularly to a recording method for search data in a VTR or the like.

[Prior art 1 Helical scan type VTR (for example, 1/2 inch, 8
In a video and still image search device using
Usually, a chapter number corresponding to the first address of the video to be searched is recorded on the recording track at the beginning of the magnetic tape.

FIG. 2 shows a conventional recording method for this type of search data, in which the search data is recorded at a specific position on a video track formed by a rotating head of a VTR, for example, in 15 horizontal sections (from the switching position of the rotating head). 15H) One chapter worth of data is recorded in the second column.

The magnetic tape on which such search data is recorded is
When set to T''R, the search device sequentially reads the search data on the magnetic tape before searching, records the first address of the chapter and the corresponding start address, such as the reel counter value of a VTR, in the memory within the device. The search device enters a standby state.By inputting a chapter number from the outside, the search device indexes the corresponding start address on the memory, fast-forwards the magnetic tape to the start address, and switches the VTR to playback mode or still image from the start address. By entering the mode state, searching and cueing of the desired image is executed.Such search devices, especially simple search devices, detect errors in the search data (parity, C
RC code, etc.), but it does not have an error correction function (cross interleaving, Reed-Solomon, etc.), so data is lost due to dropouts and the like that exist in the magnetic recording medium.

Therefore, in the conventional search data recording method, the same search data is recorded in, for example, eight consecutive recording tracks. That is, the search data for chapter 1-1 is recorded on consecutive tracks T1 to T8, and then the search data for chapter 1-2 is recorded on recording track T9.
~T17, and the search data for chapter 3-4 was similarly recorded in recording tracks Tn-s~Tn. This prevents signal dropouts.

However, in such a conventional search data recording method, when the number of chapters becomes enormous due to the inclusion of still images, it takes a long time to read the search data.

For example, to read 256 chapters on a current 1/2 inch VTR, approximately 34 seconds are required in 8-track continuous recording mode.

In addition, it is known that in VTRs, there is an effect of the difference in adhesion between the leader tape and the magnetic tape, which is commonly known as ``depressing'', and data reading and errors at the beginning of the tape are about 20 times worse than those near the middle. There is a possibility of a collective data error in this part.

Such dropouts and data reading errors are caused by
In the case of video information, it is visually compensated by a dropout compensation circuit, but in the case of search data, it cannot be compensated, resulting in a data error.

Furthermore, a data error also occurs if there are scratches or tape folds on the magnetic tape.

[Object of the Invention] The present invention aims to provide a recording method that eliminates the possibility of data loss due to scratches on the tape, tape bends, and the effects of "rolling", and further reduces the time required to read search data. purpose.

[Structure 1 of the Invention The magnetic recording and reproducing method of the present invention records a plurality of units of recorded data one unit at a time on a plurality of recording tracks in a predetermined order, and records such recording on a plurality of recording tracks. It is characterized by being repeated repeatedly.

This invention will be described below with reference to one embodiment.

In FIG. 1, the leading portion 10 of the magnetic tape 1 is a retrieval data recording portion, and the recording tracks T1 to Tn in this leading portion are, for example, eight blocks Bl-B8.
For example, if there are 16 chapters from 1-1 to 3-4, 16 recording tracks are allocated to each block.

For example, in the block B1+, the first recording track T1 contains search data for chapter 1-1,
Search data for chapters 1-2 is recorded in the second recording track T2, and in the same way, each recording track is sequentially recorded.
Chapter 1-3.1-4.2- on racks T3 to T16
1.2-2. ..., 3-3, 3-4 are recorded in order. In the second to eighth blocks B2 to B8, the search data for each chapter 1-1 to 3-4 is recorded on each recording track in the same manner as described above.

Note that an image recording portion 12 follows the recorded portion of search data.

VT the magnetic tape with the search data recorded as above.
When it is set to R and a search is performed, the video head sequentially scans the recording tracks T1 to T16 of the first block B1,
The search data obtained by scanning is sequentially read out, the search data is checked for errors, and if there is no error, it is stored in the memory.

If there is no error in the result of reading out the search data in the first block B1, the reading of the search data is finished and the actual image search begins.

If it is found that there is an error in the search data in the first block B1, the second block B2 is scanned and the search data in which the error occurred in the first block is read out from the second block. If there is an error in the second block B2, the third block B3 is further scanned.

In this way, the search data is error-free,
Finish reading the search data.

As described above, in this invention, since the search data is recorded in units of plots, the data is distributed and it is possible to deal with collective errors caused by scratches or folds on the magnetic tape. Even if a part of the first block collectively becomes an error due to the influence of ``, the probability that the same data in the second block will become an error is reduced.

Therefore, although it depends on the probability of error occurrence, it is expected that reading the third block will complete the acquisition of error-free search data.

Therefore, the time required for searching can be reduced.

Also, second. Third. ..., as you progress to the 8th block, “
It is possible to deal with missing tweet data by reducing the influence of "sleeping", and it is also possible to shorten the time required to read search data.

On the other hand, in the case of a general β or VH8 type helical scan VTR, two heads are used for normal playback, but these two heads are used for special playback (slow, still), so normally These two heads have different head widths.

- In the example, for a track pitch of 58 μm, the R channel head is 58 μm and the L channel head is 40 μm.
It is μM. In this case, the track deviation is 10 μm.
If so, the R head output will be (58-10)158==83% and the L head output will be (40-10)158==52%.

Furthermore, when retrieval data is read using the 2nd and 2nd heads, the reproduction output of the L head is lower than that of the R head, and more errors occur.

In the example shown in FIG. 2, the number of chapters is 16, so the data of chapters 1-1 of the first block and the data of chapters 2, 3, etc.・・・
・The data of chapter 1-1 of all the eighth blocks will be reproduced by the same head.

In other words, even (odd) numbered chapter data has fewer errors, but odd (even) numbered chapter data has more errors, and many blocks must be read to eliminate errors. It is necessary to take it out.

Therefore, if the number of chapters is even, such as 16, 1
If two dummy chapters are inserted and the number of chapters is 17, chapters 1-1 of each block will use alternate heads such as L head, R head, L head, R head, and it will take time to eliminate errors. be shortened.

[Effects of the Invention] As described in detail above, the present invention records various data such as image search data on a videotape in a distributed manner on a plurality of recording tracks within one block, and also records a plurality of such blocks in a plurality of recording tracks. The data is recorded in a distributed manner, so that even if there is a scratch or the like in one block of the tape, the error can be corrected using data recorded in other blocks. This reduces the probability of error occurrence and reduces the time required to read error-free data.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the search data recording method of the present invention, and FIG. 2 is a diagram showing a conventional search data recording method. Bl, B2...Block T1. T2. ..., Tn...recording track.

Claims (1)

[Claims] (1) Magnetism characterized by recording a plurality of units of recording data one unit at a time on a plurality of recording tracks in a predetermined order, and repeating such recording multiple times on other recording tracks. Recording and playback method.