JPS60177406A - Digital signal reproducer - Google Patents

Abstract

PURPOSE:To produce no omission of data nor impairment of data continuity even in case the driving direction of a recording medium is inverted, by recording the same data with overlap to both record initiation parts of the 1st and 2nd recording directions. CONSTITUTION:The first data block of the coming-back route of a magnetic tape 7 may possibly have an omission. Therefore the comparison of a comparator 18 is cancelled for the first data read out of the 2nd memory 15. Then the comparator 18 starts comparison at and after the 2nd readout data. When the comparator 18 detects the coincidence of data, a coincidence output is delivered. A selector 19 selects the output given from the memory 15 in place of the output given from the 1st memory 14 in response to the coincidence output. Therefore the data on new blocks are read out sequentially out of the memory 15. Then the selector 19 delivers data which have no omission and secure the continuity.

Description

Detailed Description of the Invention [Technical Field of the Invention J] The present invention relates to a digital signal reproducing device, and more particularly to a digital signal reproducing device that can automatically reciprocate and reproduce digital signals recorded reciprocally on a recording medium such as a magnetic tape. .

[Prior Art] Conventionally, in tape recorders, video tape recorders, etc., so-called auto-reverse mechanisms (automatic reversing mechanisms) have been used.
There was one equipped with With this auto-reverse mechanism, the running direction of the magnetic tape can be automatically reversed, so reciprocating recording and reciprocating playback can be performed automatically without flipping the cassette tape or changing the reel-to-reel tape. I can do it. However, in the conventional auto-reverse mechanism, when shifting to reverse running, it takes several tens of milliseconds to several hundred milliseconds to return to a normal state in which recording or reproduction is possible again.

As a result, there was a drawback that the sound and picture were cut out at the part where the vehicle was reversed.

[Summary of the Invention] This invention was made to eliminate the drawbacks of the conventional ones as described above, and provides a recording medium in which a digital signal is recorded in advance in a reciprocating manner, and the same information is recorded redundantly on the forward and backward paths in the reverse recording section. When reproducing the data, the reproduced data before and after the reverse playback is stored in separate storage means, and the readout of data from the storage means is temporally controlled. This eliminates data loss during the reverse playback and improves the quality of the data. The object of the present invention is to provide a digital signal reproducing device that can perform reproduction without impairing continuity.

The above objects and other objects and features of the invention will become more apparent from the following detailed description with reference to the following.

[Embodiment of the Invention] FIG. 131 is a block diagram showing the configuration of a recording system in a tape recorder according to an embodiment of the invention.

In the figure, an input terminal 1 is supplied with a recorded ε signal, that is, a digital signal obtained by sampling, quantizing, and encoding a continuous analog signal.

A digital signal input from this input terminal 1 is applied to a memory 2 and stored therein. Reading and filling of the memory 2 is controlled by an address control circuit 3. A reverse command signal is applied to this address control circuit 3 from an input terminal 4. The digital signal read from the memory 2 is modulated into a recordable signal by the modulation circuit 5, and then applied to the magnetic head 6 and recorded on the magnetic tape 7.

FIG. 2 is a diagram showing an input data string to the memory 2 shown in FIG. 1 and an output data string read from the memory 2. The reversal recording operation will be explained below with reference to FIG.

In FIG. 2, each block @ to O in the input data string is a block-contained digital signal group recorded on the magnetic chip 17, distributed over multiple tracks, and with frame synchronization signals, CRC, etc. added. recorded.

000 to 111 shown in each block are memory 2
means the address to write to. On the other hand, [share]~O in the output data string from the memory 2 means each block of the digital signal group to be read, and OOO~111 shown in each block means the read address of the memory 2. Further, FIG. 2 shows that the input data string and the output data string match in time series in a vertical relationship. First, in a normal state, input data to the memory 2 is stored in an area expressed by 2 bits OO to 11 according to a write address from the address control circuit 3. On the other hand, from the address control circuit 3 to the memory 2
The subsequent address given to is set to follow the write address, and under normal conditions is shifted by 2 bits, or 2 blocks, from the write address.

In this situation, when a memory preset command is output several blocks before the reverse operation starts, the write address is set to expand the memory area, and the 3 bits from 000 to 111 are set. It becomes stored in the area where it is expressed. On the other hand, the following addresses are
When it is detected that the reverse operation has started, reading is redone from the data block two blocks earlier, and subsequent addresses are expanded and data is output from the area expressed by 3 bits from 000 to 111. When recording is performed by the operation described above, the data output from the memory 2 is recorded on the magnetic tape 7 as shown in FIG.

As shown in FIG. 3, in the two blocks before and after the start of reverse recording, the same block is recorded in the forward and backward passes. However, it is quite conceivable that some of the first data on the return trip may be lost due to time loss during inversion recording.

FIG. 4 is a block diagram of a reproduction system according to an embodiment of the present invention, and as shown in FIG. 3, data recorded in reverse on the forward and backward passes can be read out continuously without data loss. be. In the figure, the signal reproduced from a magnetic tape 7 by a reproducing head 10 is applied to an amplifier circuit 11, where it is amplified, and then applied to a recovered data detection circuit 12, where it is converted into a complete binary signal. The output of the data detection circuit 12 is applied to an am circuit 13 and demodulated, and then applied to a first memory 14 and a second memory 15.

The first memory 14 and the second memory 15 each include:
Successive address control circuits 16 and 17 are connected to control respective read addresses. 1st
The data read from the memory 14 is sent to the data comparator 18
is applied to one input of the selector 19, and also applied to one input of the selector 19. The data read from the II2 memory 15 is applied to the other input of the data comparator 18 and the other input of the selector 1'9. A data comparator 18μ compares the data from the first memory 14 and the data from the second memory '15 for each block and detects whether or not they match. The detection result of data comparator 18 is applied to selector 19 and successive address control circuit 17. On the other hand, the reverse control circuit 8 controls the reversal of the running direction of the magnetic tape 7. The reverse control circuit 8 also controls the rotational speed of the capstan 9, that is, the traveling speed of the magnetic tee 17. A reverse advance command is given to this reverse control circuit 8, and the reverse operation is started after a certain period of time from this reverse advance command. Further, when the reverse operation is completed, the reverse control circuit Me outputs a reverse completion signal and supplies it to the successive address control circuit 17.

The read address control circuit 17 starts reading the second memory 15 a predetermined time after receiving the reverse completion signal.

FIG. 5 shows a write data string to the first memory 14 and an induced data string from the first memory 14, and a write data string to the second memory 15 and an induced data string from the second memory 15. It is a diagram. In addition, in this FIG. 5, time l! moves from the right side of the drawing to the left side. It shows the general information. Further, in the figure, OOO-111 at the top of each block indicates a write address or read address to the memory, and numbers 6-28 at the bottom of each block mean the absolute number of the data block. Hereinafter, with reference to FIG. 5, the operation of the reproducing system shown in FIG. 4 during reversal reproduction will be explained.

First, APC (Auto phase Control) is applied to the outgoing path of the magnetic tape 7 at 6' during normal reproduction, and the reproduced data block from the magnetic tape 7 is matched with the successive address from the read address control circuit 16. The information is written to the first memory 4 in synchronization. Here, a reverse warning command is given to the reversal control circuit 8 several blocks before starting the reverse operation. In response to this reverse warning command, the reverse control circuit 8' cancels the APC and instructs the capstan servo controlling the tape feeding speed to increase the tape feeding speed. As a result, the feeding speed of the magnetic tape 7 is increased, and a large amount of data can be reproduced in a short time. At this time, the feeding speed of the magnetic tape 7 is the first memo of the reproduced data.

The selection is made within a range in which the PLL that generates the reproduced clock for generating the address counter to be loaded into the first memory 4 does not become unlocked, and within a range in which the area for storing data in the first memory 4 does not overflow. . Further, in response to the reverse notice command, the write address of the first memory 4 is expanded from 2 bits to 3 bits. After the feeding speed of the magnetic tape 7 is increased as described above, when the last data on the outward path of the magnetic tape 7 is reproduced,
Reverse control circuit 8 starts reverse operation. This reverse operation reverses the running direction of the magnetic tape 7 and rotates the reproducing head 10 so that data recorded on the backward path of the magnetic tape 7 can be reproduced. When such a reverse operation is completed, the reverse control circuit 8
The magnetic chip 77 is run at a faster feed speed than the normal playback speed. At this time, the data reproduced from the magnetic tape 7 is written into the second memory 15.

On the other hand, reading of data from the first memory 14 is always performed sequentially at a constant cycle, regardless of an increase in the feeding speed of the magnetic tape 7. Therefore, the data written to the first memory 14 after jI, that is, the magnetic tape 7
The final data readout on the forward path is carried out quite late from the start of reverse. At this time, selector 19
selects and outputs data from the first memory 14. On the other hand, when the reverse operation is completed and writing of the first block of playback data (writing to the second memory 15) is completed, the successive address control circuit 17
Data reading from the second memory 15 is started in synchronization with the data reading cycle at step 4.

At this time, data on the outward path of the magnetic tape 7 is also being read from the first memory 14. In this state, the read data of the first memory 14 and the second memory 15 is provided to the data comparator 18, and it is detected whether or not both data match. If the data do not match, a mismatch output is derived from the data comparator 18. This mismatch output causes the selector 19 to maintain the state in which the output from the first memory 14 is selected. Furthermore, this coincidence output causes the successive address control circuit 17 to send the second memory 1
Update of the read address given to 5 is stopped. Therefore, the same data block is repeatedly read from the second memory 15. In contrast, the read address given to the first memory 14 advances one block at a time. In this state, the data comparator 18 compares data block by block. Thereafter, the output of the first memory 14 and the output of the second memory 1.
This state is repeated until the output of No. 5 matches the output of No. 5.

However, the data block repeatedly read from the second memory 15 at this time is 111 on the inverted recording portion of the magnetic tape 7.
It is necessary to select a normal data block that is one of the blocks (blocks 20 or 21) recorded m and in which no data is missing due to inversion recording. In this actual IM example, since there is a possibility that the first data block on the return path of the magnetic tape 7 will be missing, the second memory 1
The data comparison in the data comparator 18 is canceled for the first data read from the first data, and the data comparison in the data comparator 18 is started from the second data read out by V first. Here, when a data match is detected by the data comparator 18, a match output is derived. In response to this match output,
The selector 19 selects the output from the second memory 15 instead of selecting the output from the first memory 14. Further, the update of the read address in the read address control circuit 11117 is stopped. Therefore, new blocks of data are successively read from the second memory 15. Therefore, the selector 19 outputs data without any data loss or continuity.

Note that although the embodiments described above have been shown as having both a recording system and a reproducing system, the present invention may be of the type having only a reproducing system. In this case, the condition is that the digital signal is re-recorded in the state shown in FIG. 3 on the magnetic tape to be reproduced.

Further, in the above-described embodiment, the upper and lower stages of the magnetic tape are divided into two parts and played back and forth, but the present invention can also be applied to, for example, a comb-shaped track format.

[Effect of the Invention J As described above, according to the present invention, when reproducing digital signals from a magnetic tape on which digital signals have been recorded reciprocally, there is no data loss even if the running direction of the recording medium is reversed. A digital signal reproducing device that does not lose data continuity can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a recording system in an embodiment of the present invention. FIG. 2 is a diagram showing an input data string to the memory 2 shown in FIG. 1 and an output data string from the memory 2. FIG. 3 shows an inversion of the magnetic tape recorded by the recording system shown in FIG. 4 is a diagram showing a recording frame in a recording section. FIG. 4 is a block diagram of a reproduction system in an example of an actual flvI of the present invention. FIG.
FIG. 2 is a diagram chronologically representing a data string passed to and a data string read from the first memory 14, a data string written to the second memory 15, and a data string read from the second memory 15. In the figure, 2 is a memory, 3 is an address control circuit, 5 is a modulation circuit, 6 is a recording head, 7 is a magnetic tape, 8 is a reverse control circuit, 9 is a capstan, 10 is a reproduction head,
11 is an amplifier, 12 is a data detection circuit, 13 is a demodulation circuit, 14 is a first memory, 15 is a second memory, 16 and 1
7 is a read address control circuit, 18 is a data comparator, 19th representative Masu Oiwa h1 diagram

Claims (1)

[Claims] A V4 system for reproducing a digital signal obtained by sampling, m-digitizing, and encoding a continuous analog signal from a recording medium on which the digital signal is recorded, wherein the magnetic tape is the first! The digital signal is recorded along the direction of 11, the recording direction is reversed midway, and the digital signal is recorded along the direction of m2, which is opposite to the direction of wX1, and the recording direction of ml is The same data is recorded redundantly at the recording end of the magnetic tape and the recording start of the second recording direction, and the reproduction position of the magnetic tape approaches the recording end of the first recording direction. When the running direction of the magnetic tape is reversed, means for reversing the running direction of the magnetic tape, storage means for storing reproduced data before the running direction of the magnetic tape is reversed, and storage means for storing playback data before the running direction of the magnetic tape is reversed; a second storage means for storing reproduction data; a means for increasing the running speed of the magnetic tape before and after the running direction of the magnetic tape is reversed than the running speed during normal reproduction; and storage in the first storage means. a first successive reading means for sequentially reading out the reproduced data stored in the second storage means at a constant cycle; a second reading means for sequentially reading out the reproduced data stored in the second storage means at the constant cycle; means for detecting whether the data read from the first storage means and the data read from the second storage means match; reading the wI2 when the detection means detects a mismatch between the data; Digital! i playback device.