JP2000348432A - Magnetic recording and reproducing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a running tape from stopping for a moment and also prevent a delay from being generated in data reproduction due to a rewind/re- tracking or the like at the time of re-readout of data in the case where a readout rate on a host computer side is low in a magnetic recording and reproducing apparatus using a rotary cylinder. SOLUTION: A signal read out by a rotary head is processed in a reproduced signal-processing section 1 to temporarily stored in a buffer memory 4. A memory capacity monitoring section 5 monitors the amount of data which have not yet been transferred to the buffer memory 4. A reproduction seed control section 6 outputs to a capstan control section 3 an instruction for lowering a transfer speed of a magnetic tape to 1/3, 1/5,..., in the case where the transfer rate from a host I/F section 8 to a host computer 9 has become low.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus for recording / reproducing digital data compressed or uncompressed on a magnetic tape by a rotary head, and more particularly to a digital data storage device.

[0002]

2. Description of the Related Art As a large-capacity backup device for computer data, there is a digital data storage device for recording and reproducing digital data by a rotary head using a magnetic tape of 4 mm or 8 mm width as a recording medium. In these devices, since compressed or uncompressed digital data is transferred discontinuously from a computer, during recording, the data is temporarily stored in a memory provided in the device and recorded on a magnetic tape according to a predetermined format. You. At the time of reproduction, a signal read from a magnetic tape is reproduced according to a predetermined format, temporarily stored in a memory in the apparatus, and data is transferred according to a request from a computer.

[0003]

Generally, a data storage device is connected to a general-purpose network of a computer such as SCSI, and when reproducing data, data is transferred to a hard disk or the like of a host computer via the network in response to a request from the computer. Sent. Usually, a plurality of accesses are always performed on this network, and the transfer speed of the network may be lower than the reproduction speed of the data storage device.

[0004] Further, the data storage device is provided with a data compression function, and depending on data, the compression ratio may be high. In this case, since the amount of decompressed data becomes large with respect to the reproduced data from the magnetic tape, it is necessary to transfer a large amount of data to the host computer,
The data reproduction speed of the magnetic tape may exceed the transfer speed of the network.

In such a case, since the buffer memory in the apparatus overflows, the reproduction of the magnetic tape is temporarily stopped, and after the data in the buffer memory is transferred, when the free space is sufficiently secured. The reproduction of the magnetic tape is performed again. At this time, in the magnetic recording / reproducing apparatus using the rotary head, since it is necessary to perform tracking, the magnetic tape is rewound once by a predetermined amount, and after performing tracking, data reproduction is restarted from a desired position. Has become. Since the rewinding operation and the re-tracking operation take several seconds, there is a problem that the average data transfer speed is extremely deteriorated as compared with the case where re-tracking does not occur. Further, when the rewinding operation and the re-reproducing operation are frequently performed, tension is applied to the magnetic tape, so that there is a problem that the damage to the magnetic tape is increased.

The present invention has been made in view of such a conventional problem, and realizes a data reproduction speed corresponding to a network transfer speed, thereby preventing a decrease in data transfer efficiency and preventing a magnetic tape from being reduced. It is an object of the present invention to realize a magnetic recording / reproducing apparatus capable of reducing the damage of a magnetic recording to the same level as that of normal reproduction.

[0007]

According to a first aspect of the present invention, there is provided a magnetic recording and reproducing apparatus for recording and reproducing compressed or uncompressed digital data on a magnetic tape by helical scanning of a rotary head mounted on a rotary cylinder. And
A reproduction signal processing circuit for processing a signal reproduced by the rotary head in accordance with a predetermined format; a buffer memory for temporarily storing digital data processed by the reproduction signal processing circuit; and a buffer memory in response to a request from a host computer A host interface unit that transfers the data to the host computer side, and a capstan control unit that transfers the magnetic tape at a specified speed.
A memory capacity monitoring unit that monitors the amount of data in the buffer memory during data reproduction; and a monitoring result of the memory capacity monitor, the data transfer speed requested by the host computer is higher than the data read speed during normal reproduction by the rotary head. When the speed becomes low, in order to reduce the data reproduction speed, the capstan control unit is instructed to gradually reduce the traveling speed of the magnetic tape while keeping the rotation speed of the rotary cylinder the same as during normal reproduction. And a playback speed control unit for outputting.

According to a second aspect of the present invention, there is provided a magnetic recording and reproducing apparatus for recording and reproducing compressed or uncompressed digital data on a magnetic tape by helical scanning of a rotary head mounted on a rotary cylinder. A reproduction signal processing circuit for processing a signal reproduced by the head in accordance with a predetermined format; a buffer memory for temporarily storing digital data processed by the reproduction signal processing circuit; and data in the buffer memory in response to a request from a host computer. A capstan control unit for transferring the magnetic tape at a designated speed, a memory capacity monitoring unit for monitoring the amount of data in the buffer memory during data reproduction, and the memory According to the monitoring result of the capacity monitor, When the data transfer speed requested by the host computer is lower than the data read speed at the time of normal reproduction, in order to reduce the data reproduction speed, in a state where the rotation speed of the rotary cylinder is kept the same as during normal reproduction, An instruction to gradually decrease the traveling speed of the magnetic tape is output to the capstan control unit, and when the data transfer speed to the host computer is increased, the instruction to gradually increase the traveling speed of the magnetic tape is issued. A reproduction speed control unit for outputting to the capstan control unit.

According to a third aspect of the present invention, there is provided a magnetic recording and reproducing apparatus for recording and reproducing compressed or non-compressed digital data on a magnetic tape by helical scanning of a rotary head mounted on a rotary cylinder. A reproduction signal processing circuit for processing a signal reproduced by the head in accordance with a predetermined format; a buffer memory for temporarily storing digital data processed by the reproduction signal processing circuit; and data in the buffer memory in response to a request from a host computer. A capstan control unit for transferring the magnetic tape at a designated speed, a memory capacity monitoring unit for monitoring the amount of data in the buffer memory during data reproduction, and the memory According to the monitoring result of the capacity monitor, When the data transfer speed requested by the host computer is lower than the data read speed at the time of normal reproduction, in order to reduce the data reproduction speed, in a state where the rotation speed of the rotary cylinder is kept the same as during normal reproduction, An instruction to reduce the running speed of the magnetic tape to an odd number during normal reproduction is output to the capstan controller, and one data track on which azimuth recording is performed by the rotary head is scanned at least once. And a playback speed control unit.

According to a fourth aspect of the present invention, there is provided a magnetic recording and reproducing apparatus for recording and reproducing compressed or non-compressed digital data on a magnetic tape by helical scanning of a rotary head mounted on a rotary cylinder. A reproduction signal processing circuit for processing a signal reproduced by the head in accordance with a predetermined format; a buffer memory for temporarily storing digital data processed by the reproduction signal processing circuit; and data in the buffer memory in response to a request from a host computer. A capstan control unit for transferring the magnetic tape at a designated speed, a memory capacity monitoring unit for monitoring the amount of data in the buffer memory during data reproduction, and the memory According to the monitoring result of the capacity monitor, When the data transfer speed requested by the host computer is lower than the data read speed at the time of normal reproduction, in order to reduce the data reproduction speed, in a state where the rotation speed of the rotary cylinder is kept the same as during normal reproduction, A reproduction speed control unit that outputs an instruction to gradually decrease the traveling speed of the magnetic tape to the capstan control unit,
Wherein the reproduction signal processing circuit performs a data reproduction process only on track data obtained by tracing the center of a track of the magnetic tape among reproduction signals obtained from the rotary head, When the rotating head does not trace the center of the track on the magnetic tape, the reproducing process is not performed.

According to the configuration of the first aspect, even when the transfer rate on the host computer side is reduced, the tape reproduction is not temporarily stopped or re-tracking is not performed.
Data is reproduced stably.

According to the second aspect of the present invention, the tape running speed is increased stepwise to the normal reproduction speed in accordance with the data request speed of the host computer, so that the fastest data can be transferred without stopping the tape running. Reading speed can be secured.

According to the third aspect of the present invention, the amount of data in the buffer memory is monitored during data reproduction, and when the data transfer speed required by the host computer becomes lower than the digital data read speed during normal reproduction, By setting the tape running speed to an odd number (1/3, 1/5,...), One data track on which azimuth recording is performed passes at least once by a rotary head, thereby reducing the number of tracks by one. Data can be reproduced.

According to the configuration of the fourth aspect, once every three times at the time of 1/3 speed reproduction, and once every five times at the time of 1/5 speed reproduction.
Trace the center of the track at a rate of times. By processing the reproduced data, the power consumption can be reduced by reducing the memory area for storing data and reducing unnecessary operations in addition to the above operation.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic recording / reproducing apparatus according to an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a block diagram showing a basic configuration of a magnetic recording / reproducing apparatus according to the present embodiment. This magnetic recording / reproducing device
A rotary cylinder, a spindle motor for rotating and driving the rotary cylinder, a reproducing head and a recording head (hereinafter also referred to as a rotary head) attached to a plurality of locations on an outer peripheral portion of the rotary cylinder, a capstan motor for transporting a magnetic tape, and a pinch roller. The recording / reproducing mechanism is shown in FIG. 1, but is not shown in FIG. Also, as signal processing and control units of the magnetic recording / reproducing device, a reproduced signal processing unit 1, an error correction processing unit 2, a capstan control unit 3, a buffer memory 4, a memory capacity monitoring unit 5, a reproduction speed control unit 6, a data compression / An expansion unit 7 and a host interface unit (host I / F unit) 8 are provided. Further, a host computer 9 for performing data processing using the reproduction data of the magnetic recording / reproducing apparatus is provided.

In the magnetic recording / reproducing apparatus having such a configuration, a reproduced signal read out from the reproducing head of the rotary cylinder and digitized is input to the reproduced signal processing section 1.
The reproduction signal processing unit 1 performs data processing on the digital reproduction signal according to a predetermined format, and stores the reproduction data in the buffer memory 4. Next, the error correction processing unit 2 checks the presence or absence of an error in the reproduction data stored in the buffer memory 4, and if the error is detected and the error can be corrected, the error correction of the reproduction data is performed. In the case of compressed data, the reproduced data in the buffer memory 4 on which the error correction has been performed is decompressed by the data compression / decompression unit 7 and transmitted from the host I / F unit 8 to the host computer 9 via the general-purpose network. Transferred continuously or intermittently. When the reproduced data is uncompressed data, the data is transferred to the host computer 9 via the host I / F unit 8 through the data compression / decompression unit 7.

At the time of normal reproduction, when the transfer speed between the host I / F unit 8 and the host computer 9 is faster than the data reproduction speed of the magnetic tape, the host I / F unit 8 stores data in the buffer memory 4. Each time transfer becomes possible, data transfer is performed to the host computer 9. At this time, the capstan control unit 3 transfers the magnetic tape at the normal reproduction speed (double speed ratio 1) according to the instruction from the reproduction speed control unit 6, and the reproduction head continuously reproduces the signal.

Next, a case where the transfer speed between the host I / F unit 8 and the host computer 9 is lower than the data reproduction speed will be described. Such a state may occur when the network is congested or the processing capacity of the host computer 9 is low, when the compression rate of the reproduction data is high, and the amount of data transferred to the host computer 9 after decompression of the reproduction data becomes large, This occurs when the reproduction data stored in the buffer memory 4 always exceeds a specific ratio. In such a case, the reproduction speed control unit 6 determines from the monitoring result of the memory capacity monitoring unit 5 that the reproduction speed is too high, and reduces the tape reproduction speed to the capstan control unit 3 in order to reduce the data reproduction speed. Give instructions to step down. Further, the reproduction speed control unit 6 gives the reproduction signal processing unit 1 a control signal for performing a thinning-out reproduction process in accordance with the speed stage. This prevents the magnetic tape from frequently stopping due to overflow of the buffer memory 4.

Further, in the reproducing state in which the running speed of the magnetic tape is reduced as described above, the reproduced data in the buffer memory 4 is always constant due to factors such as the elimination of network congestion and a reduction in the compression rate of the compressed data. In the case of the following, the reproduction speed control unit 6 determines that the reproduction speed is too slow. At this time, the reproduction speed control unit 6 issues an instruction to the capstan control unit 3 to increase the tape traveling speed, and performs control to gradually increase the traveling speed of the magnetic tape. Further, the reproduction speed control section 6 gives a control signal to the reproduction signal processing section 1 to perform the thinning-out reproduction processing corresponding to the above-mentioned speed step. In this way, a decrease in the data transfer speed to the host computer 8 due to the underflow of the buffer memory 4 is prevented.

The memory capacity monitor 5 monitors the amount of data in the buffer memory 4 during data reproduction, and when the data transfer speed required by the host computer 9 becomes lower than the data read speed during normal reproduction by the rotary head. ,
To reduce the data reproduction speed, the reproduction speed control unit 6 outputs to the capstan control unit 3 an instruction to gradually reduce the running speed of the magnetic tape while keeping the rotation speed of the rotary cylinder the same as during normal reproduction. . The control method at this time will be described with reference to the flowchart of FIG.

In step S1, when data is reproduced from the magnetic tape by scanning of the rotary head, the data is temporarily stored in the buffer memory 4 via the reproduction signal processing unit 1. In step S2, the memory capacity monitoring unit 5 monitors the used area or free space of the buffer memory 4. In the next step S3, it is checked whether or not the buffer memory 4 has been filled with data. If not, the flow proceeds to step S4, and if so, the flow proceeds to step S6. In step S4, it is determined that the data read speed (read speed) is equal to or less than the data transfer speed (host speed). In this case, step S5
The reproducing speed control unit 6 outputs to the capstan control unit 3 an instruction to maintain the current running speed of the magnetic tape.

When the process proceeds from step S3 to step S6, it is determined that the data read speed exceeds the data transfer speed. In this case, proceeding to step S7, the reproduction speed control unit 6 outputs to the capstan control unit 3 an instruction to lower the traveling speed of the magnetic tape by one step. In this way, data reproduction is continued.

FIG. 3 is an explanatory view showing the trajectory of the reproducing head at the time of 1-time speed reproduction (times ratio 1/1). Here, the magnetic tape 10 is transported in a running direction 11 indicated by an arrow.
In FIG. 3, tracks 101,
The track 101 is a + azimuth track B0, the track 102 is a −azimuth track B0, the track 103 is a + azimuth track A1, and the track 104 is a −azimuth track B1. Also, the trajectory 105 shown by a solid line or a broken line,
106, 107 and 108 are the tracks 101 and 10 respectively.
The trajectory of the reproducing head at 2, 103 and 104.
The trajectory 105 is the trajectory of the + azimuth reproducing head A, the trajectory 106 is the trajectory of the − azimuth reproducing head B, and the trajectory 107 is the trajectory of the + azimuth reproducing head A.
08 indicates the trajectory of the azimuth by the reproducing head B. Here, it can be seen that the reproducing heads A and B are respectively moved by two track pitches in the direction opposite to the running direction 11 of the magnetic tape 10.

FIG. 4 shows a half speed reproduction (1/2 speed ratio).
FIG. 4 is an explanatory diagram showing the trajectory of the reproducing head. Track 10
Tracks 1, 102, 103, and 104 are recorded at the normal speed in this order. The track 101 is a track A0 of + azimuth, the track 102 is a track B0 of -azimuth, and the track 103 is a track A1 of + azimuth. , Track 104-Track B of Azimuth
Setting to 1 is the same as in FIG. Unlike FIG. 3, the transfer speed 11b of the magnetic tape 10 indicated by the solid arrow is slower than the 1x transfer speed 11a indicated by the broken arrow. As shown by the solid line, the reproducing head A traces four tracks four times,
Similarly, as shown by the broken line, it can be seen that the reproducing head B traces four tracks four times. That is, the movement of one track pitch is performed.

During a certain scanning period, the reproducing head A traces the tracks 101 and 103 of the normal azimuth, that is, + azimuths as shown by the trajectories 105 and 109. Azimuths, that is, -azimuth tracks 102 and 104 are traced as shown in trajectories 107 and 111. Orbit 1
At 07 and 111, despite being on-track,
Since it is reverse azimuth, a reproduced signal cannot be obtained.

On the other hand, the trajectory of the reproducing head B becomes trajectories 106, 108 and 110 indicated by broken lines, and traces the boundary of each track.
A reproduced signal with a high N cannot be obtained. FIG.
Is a case of tracing once along every two tracks along the center of the normal track to obtain a normal reproduction signal, but the same applies when not tracing along the center of the normal track. In this case, the reproduction signals of the reproduction head A and the reproduction head B both have a low S / N. When the speed ratio is 1 / N, such an inconvenience occurs when N is an even number.

FIG. 5 shows a 1/3 speed reproduction (1/3 speed ratio).
FIG. 4 is an explanatory diagram showing the trajectory of the reproducing head. Track 10
Tracks 1, 102, 103, and 104 are recorded at normal speed, track 101 is a track A0 of + azimuth, and track 102 is a track B0 of -azimuth.
The track 103 is a track A1 of + azimuth and the track 104 is a track B1 of -azimuth as in FIGS. Unlike FIG. 3, 1 /
At the time of 3 × speed reproduction, as shown by the solid line, the reproducing head A
It can be seen that the track is traced six times, and that the reproducing head B traces four tracks six times, as also indicated by the broken lines.

Even in the case of 1/3 speed reproduction, for example, the trajectory 108 of the azimuth reproducing head B passing through the center of the azimuth track 102 substantially corresponds to the track 102
Coincides with the center of The reason why the track including the other tracks and the trajectory of the reproducing head A or B become parallel even at 1 / N speed reproduction is as follows. That is, in the normal reproduction, the relative speed of the recording or reproducing head with respect to the magnetic tape is extremely higher than the transport speed of the magnetic tape.
For this reason, even if the transfer speed of the magnetic tape is slower than during normal reproduction, the track tilt angle of the reproduction head with respect to the magnetic tape hardly changes. Therefore, during the subsequent scanning, the trajectory of the reproducing head B of -azimuth is 110, 112,
It looks like 114. Therefore, after three cycles from the trajectory 108, the trajectory 114 becomes the trajectory 114, and the center of the azimuth track 104 can be traced.

Similarly, the trajectory 105 of the + azimuth reproducing head A passing through the center of the + azimuth track 101 traces the center of the + azimuth track 103 after the rotary cylinder rotates three times through the orbits 107 and 109. You can see that.

FIG. 6 is a timing chart of the reproduction signal processing at the 1/3 speed when the magnetic tape is wound around the rotary cylinder by 90 °. As shown in FIG. 6A, a reproduced signal shown in FIG. 6B is obtained for each rotation of the rotary cylinder. Of the reproduced signal waveforms 13 to 19, the reproduced signal waveform 13, which is obtained when crossing the center of the recording track,
A prescribed amplitude can be obtained from 16 and 19. The reproduction signal processing unit 1 shown in FIG. 1 processes the reproduction signal waveforms 13, 16, and 19, and reproduces reproduction processing signals 20, 21, and 20 as shown in FIG.
22 is output. These reproduction processing signals are stored in the buffer memory 4 of FIG. 1 as reproduction data. Thus, the number of times of signal processing per time can be reduced, and power consumption can be reduced.

The reproduction speed control unit 6 shown in FIG. 1 controls the rotation speed to reduce the data reproduction speed when the data transfer speed required by the host computer 9 becomes lower than the data read speed during normal reproduction by the rotary head. While keeping the rotation number of the cylinder the same as during normal reproduction, the capstan control unit 3 issues an instruction to gradually decrease the traveling speed of the magnetic tape.
Output to Further, when the data transfer speed to the host computer 9 increases, the reproduction speed control unit 6 outputs to the capstan control unit 3 an instruction to gradually increase the traveling speed of the magnetic tape. The control method at this time will be described with reference to the flowchart of FIG.

In step S11 of FIG. 7, when data is reproduced from the magnetic tape by scanning of the rotary head,
Data is temporarily stored in the buffer memory 4 via the reproduction signal processing unit 5. In step S12, the memory capacity monitor 5 monitors the data storage area or free space of the buffer memory 4. In the next step S13, it is checked whether or not the data storage area of the buffer memory 4 is empty. If it is not empty, the process proceeds to step S14, and if it is empty, the process proceeds to step S16. In step S14, it is determined that the data read speed (read speed) is equal to or higher than the data transfer speed (host speed). And step S
Proceeding to 15, the reproduction speed control unit 6 outputs to the capstan control unit 3 an instruction to maintain the current running speed of the magnetic tape.

When the process proceeds from step S13 to step S16, it is determined that the data read speed is lower than the data transfer speed. In this case, proceeding to step S17, the reproduction speed control unit 6 outputs to the capstan control unit 3 an instruction to increase the traveling speed of the magnetic tape by one step. In this way, data reproduction is continued.

The reproduction speed control unit 6 shown in FIG. 1 controls the rotation speed to reduce the data reproduction speed when the data transfer speed required by the host computer 8 becomes lower than the data read speed during normal reproduction by the rotary head. While the rotation speed of the cylinder is kept the same as during normal playback, an instruction to reduce the magnetic tape traveling speed to an odd-numbered one during normal playback is output to the capstan control unit 3, and the azimuth recorded by the rotary head is output. One data track is scanned at least once. The control method at this time will be described with reference to the flowchart of FIG.

In step S21 of FIG. 8, a tape running value (reproduction speed ratio 1 / N) is set. N is 1, 3, 5
... An odd number of 2n + 1. In step S22, it is assumed that the magnetic tape is transported at a double speed ratio of 1 / N to perform tracking, and for example, on-track is performed at + azimuth A track. This track is set as the first track, and the data of the first track is read by the + azimuth rotary head.
When the rotary cylinder rotates 180 ° in the next step S23, the value of N is decremented in the next step S24. In the next step S25, it is checked whether or not N = 0. If N = 0, the process returns to step S23, and the same operation is repeated. If N = 0 in step S25, it is determined that the + azimuth rotary head is currently on-track to the second track, and the process proceeds to step S26 to read data from the current track. Step S26
Is completed, the process returns to step S21, and the same operation is repeated. In this way, the first track, the second track, the third track... Of + azimuth are scanned,
Data can be read at an odd multiple of 1/200.

[0036]

As described above, according to the present invention, the running of the magnetic tape is frequently paused in response to a change in the transfer speed of the computer network or a decrease in the data transfer speed due to a change in the compression ratio of the recording data. It is possible to perform data reproduction without performing. This prevents the data transfer efficiency from decreasing due to the stoppage of the tape running, and stops / stops the magnetic tape.
The effect of reducing tape damage due to repetition of rewinding / reproduction and reducing power consumption during low-speed reproduction can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a basic configuration of a magnetic recording and reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a control method (part 1) of a reproduction speed control unit in the magnetic recording / reproducing apparatus of the present embodiment.

FIG. 3 shows the magnetic recording / reproducing apparatus according to the embodiment;
FIG. 4 is a trace diagram of the rotating head at the time of double speed.

FIG. 4 shows the magnetic recording / reproducing apparatus according to the embodiment;
FIG. 5 is a trace diagram of the rotating head at the time of / 2 × speed.

FIG. 5 shows the magnetic recording / reproducing apparatus according to the embodiment;
FIG. 4 is a trace diagram of the rotating head at the time of ３ speed.

FIG. 6 shows the magnetic recording / reproducing apparatus according to the embodiment;
6 is a time chart of a reproduction signal obtained at / 3x speed.

FIG. 7 is a flowchart illustrating a control method (part 2) of a reproduction speed control unit in the magnetic recording / reproducing apparatus of the present embodiment.

FIG. 8 is a flowchart illustrating a control method (part 3) of a reproduction speed control unit in the magnetic recording / reproducing apparatus of the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Error correction processing part 2 Reproduction signal processing part 3 Capstan control part 4 Buffer memory 5 Memory capacity monitoring part 6 Reproduction speed control part 7 Data compression / decompression part 8 Host I / F part 9 Host computer 10 Magnetic tape 11 Magnetic tape Running direction

Claims (4)

[Claims] 1. A magnetic recording / reproducing apparatus for recording / reproducing compressed / uncompressed digital data on / from a magnetic tape by helical scanning of a rotary head attached to a rotary cylinder, wherein a signal reproduced by the rotary head is reproduced. A reproduction signal processing circuit for processing in accordance with a predetermined format; a buffer memory for temporarily storing digital data processed by the reproduction signal processing circuit; and transferring data in the buffer memory to the host computer side in response to a request from a host computer A capstan control unit for transferring the magnetic tape at a designated speed, a memory capacity monitoring unit for monitoring the data amount of the buffer memory during data reproduction, and a monitoring result of the memory capacity monitor. Data during normal playback by the rotating head When the data transfer speed requested by the host computer becomes lower than the read speed, in order to reduce the data reproduction speed, the running speed of the magnetic tape is maintained while the rotation speed of the rotary cylinder is kept the same as during normal reproduction. A reproducing speed control unit for outputting an instruction to decrease the speed in a stepwise manner to the capstan control unit. 2. A magnetic recording and reproducing apparatus for recording and reproducing compressed or uncompressed digital data on a magnetic tape by helical scanning of a rotary head mounted on a rotary cylinder, wherein a signal reproduced by the rotary head is recorded. A reproduction signal processing circuit for processing in accordance with a predetermined format; a buffer memory for temporarily storing digital data processed by the reproduction signal processing circuit; and transferring data in the buffer memory to the host computer side in response to a request from a host computer A capstan control unit for transferring the magnetic tape at a designated speed, a memory capacity monitoring unit for monitoring the data amount of the buffer memory during data reproduction, and a monitoring result of the memory capacity monitor. Data during normal playback by the rotating head When the data transfer speed requested by the host computer becomes lower than the read speed, in order to reduce the data reproduction speed, the running speed of the magnetic tape is maintained while the rotation speed of the rotary cylinder is kept the same as during normal reproduction. The capstan control unit outputs an instruction to gradually reduce the speed to the capstan control unit.If the data transfer speed to the host computer increases, the capstan control unit issues an instruction to gradually increase the traveling speed of the magnetic tape. A magnetic recording / reproducing apparatus, comprising: a reproducing speed control unit for outputting. 3. A magnetic recording and reproducing apparatus for recording and reproducing compressed or uncompressed digital data on a magnetic tape by helical scanning of a rotary head mounted on a rotary cylinder, wherein a signal reproduced by the rotary head is reproduced. A reproduction signal processing circuit for processing in accordance with a predetermined format; a buffer memory for temporarily storing digital data processed by the reproduction signal processing circuit; and transferring data in the buffer memory to the host computer side in response to a request from a host computer A capstan control unit for transferring the magnetic tape at a designated speed, a memory capacity monitoring unit for monitoring the data amount of the buffer memory during data reproduction, and a monitoring result of the memory capacity monitor. Data during normal playback by the rotating head When the data transfer speed requested by the host computer becomes lower than the read speed, in order to reduce the data reproduction speed, the running speed of the magnetic tape is maintained while the rotation speed of the rotary cylinder is kept the same as during normal reproduction. A reproduction speed control unit that outputs an instruction to reduce the speed to an odd number of times during normal reproduction to the capstan control unit, and scans one data track recorded azimuthally by the rotary head at least once; ,
A magnetic recording / reproducing apparatus comprising: 4. A magnetic recording / reproducing apparatus for recording / reproducing compressed / uncompressed digital data on / from a magnetic tape by helical scanning of a rotary head mounted on a rotary cylinder, wherein a signal reproduced by the rotary head is reproduced. A reproduction signal processing circuit for processing in accordance with a predetermined format; a buffer memory for temporarily storing digital data processed by the reproduction signal processing circuit; and transferring data in the buffer memory to the host computer side in response to a request from a host computer A capstan control unit for transferring the magnetic tape at a designated speed, a memory capacity monitoring unit for monitoring the data amount of the buffer memory during data reproduction, and a monitoring result of the memory capacity monitor. Data during normal playback by the rotating head When the data transfer speed requested by the host computer becomes lower than the read speed, in order to reduce the data reproduction speed, the running speed of the magnetic tape is maintained while the rotation speed of the rotary cylinder is kept the same as during normal reproduction. A reproduction speed control unit that outputs an instruction to reduce the speed in a stepwise manner to the capstan control unit, wherein the reproduction signal processing circuit comprises a track of the magnetic tape among reproduction signals obtained from the rotating head. Data reproduction processing is performed only on track data obtained by tracing the center of the magnetic tape, and the reproduction processing is not performed when the rotary head does not trace the center of the track of the magnetic tape. Playback device.