JPH1040638A - Data reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a time for reproduction until its final completion, which is hitherto lengthened due to a standby time at the initial reproduction of data. SOLUTION: A reproducing means consisting of a reproducing mechanism part 21 and a demodulation control part 22 is capable of reproducing data at a reproducing speed corresponding to a system clock signal Sc, and the reproduced data is temporarily stored in a buffer memory 23a constituting a buffer means and is read out by a host computer 10. On the other hand, a data writing address Aw and a data reading address Ar at each time in the buffer memory 23a are managed by a memory controller 23b constituting the same buffer means, and from a difference between them, a data accumulated amt. Db is obtained by a calculating part 24a of a reproducing control part 24 constituting the reproducing means. A control voltage of a VCO 24c for outputting the system clock signal Sc is decided and outputted by a clock control part 24b to change reproducing speed of data without overflowing the buffer memory 23a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a data reproducing apparatus, and more particularly to a data reproducing apparatus having a buffer memory for temporarily storing read data.

[0002]

2. Description of the Related Art In an optical disk reproducing apparatus using an optical disk as a data storage medium, target data is reproduced from the optical disk at a predetermined speed in accordance with a data read request from an external device. Further, the optical disk reproducing device sends the reproduced data to an external device via a bus line. In such an apparatus, the reproduced data is temporarily stored in a buffer memory provided in the optical disk reproducing apparatus. Then, the external device reads data from the buffer memory.

Therefore, if the data reading speed of the external device from the buffer memory is lower than the data reproducing speed of the optical disk in the optical disk reproducing device,
As shown in FIG. 3, as the accumulated amount L (bytes) of data in the buffer memory increases as time t elapses and the maximum storage capacity Lb (bytes) of the buffer memory is reached, the buffer memory overflows at time ta. Occurs.
As a solution to such a problem, a device disclosed in JP-A-63-29373 shown in FIG. 4 is conventionally known.

[0004] A CD-ROM reproducing apparatus 1 shown in the figure is connected to a host computer 2.
From the data read speed Sh as a data read request
(Byte / sec) and the data length Lr (byte) to be read are input. These data read speeds Sh
The data length Lr and the data length Lr are input to the calculation unit 3, which calculates a data reproduction speed Sr (byte / sec) at which the buffer memory unit 4 does not overflow.

[0005] The information on the data reproduction speed Sr is input to the clock control unit 5, and the clock control unit 5 outputs a control voltage corresponding to the data reproduction speed Sr. This control voltage is input to the VCO 6, which generates a system clock signal Sc having a cycle corresponding to the control voltage. The system clock signal Sc is input to the demodulation control unit 7, and the demodulation control unit 7 outputs the data from the data reproduction unit 8 while controlling the rotation speed of the servo motor in the data reproduction unit 8 according to the system clock signal. The data is reproduced based on the EFM signal.

[0006] The demodulation control unit 7 operating in accordance with the system clock signal Sc outputs a data reproduction speed S from the CD-ROM.
r, the data is reproduced. If the data reproduction speed Sr at this time satisfies the following condition: Sr ≦ {Lr / (Lr−Lb)} Sh (1), the buffer memory unit 4 overflows. The host computer 2 can read data continuously.

The operation of the CD-ROM reproducing apparatus 1 and the host computer 2 having the above-described configurations will be described with reference to the operation diagram shown in FIG. Assuming that a data read request is input from the host computer 2 at time t1 shown in FIG.
At time t2 when the time required for the calculation and setting of has elapsed, the state becomes the search state S, and at time t3, the state becomes the data reproduction state P. Then, the CD-ROM reproducing device 1 continuously reproduces the data until the time t5 at which the reproduction of all the data ends, without entering the middle search state S.

On the other hand, the host computer 2 enters the waiting state W at time t1 in FIG. 1B, and enters the data reading state R from the buffer memory unit 4 at time t4 after the time t3. And the host computer 2
Until the reading of all data stored in the buffer memory unit 4 is completed, data can be read continuously without entering the waiting state W.

[0009]

The above-mentioned conventional data reproducing apparatus has the following problems. After receiving the data read request from the host computer 2, it needs time to calculate and set the data reproduction speed Sr. If the data read speed Sh of the host computer 2 is low or the read data length Lr is long, the CD-ROM reproducing device 1 searches and reads data from the optical disc at a data reproduction speed Sr that is lower than normal. Reading must be performed, the speed of accumulating data in the buffer memory unit 4 becomes slow, and the time of the first search state S becomes long.

[0010] The present invention has been made in view of the above problems, and has as its object to provide a data reproducing apparatus capable of achieving higher speed.

[0011]

In order to achieve the above object, the invention according to claim 1 comprises a reproducing device for reproducing data from a data storage medium at a desired speed, and a reproducing device for reproducing data from a data storage medium. Buffer means for temporarily storing the interposed reproduced data and readable by the reading device; and the reproducing means so as not to overflow the buffer means by referring to the substantial stored data amount in the buffer means. And control means for controlling the data accumulation speed from the data.

According to the invention having such a configuration, the data reproduced from the data storage medium by the reproducing means is temporarily stored in the buffer means interposed between the reading device and the reproducing means. The stored data is read from the reading device. Here, the control means refers to the substantial stored data amount in the buffer means, and controls the data storage speed from the reproducing means so that the buffer means does not overflow. In other words, when the overflow is about to occur, the data reproduction speed is reduced to reduce the data accumulation speed, and when there is a margin, the data reproduction speed is increased again to increase the data accumulation speed.

The reproducing means may be any means capable of reproducing data from a data storage medium at a desired speed. The data storage medium may be an optical disk, a magneto-optical disk, a tape, a semiconductor element, or the like. It can be changed as appropriate. The reading device may be any device that reads data at a predetermined processing speed and sequentially processes the data, and may be an external host computer or another internal data processing unit. .

The buffer means may be any means capable of temporarily storing data substantially, regardless of the name of the buffer. Therefore, it may be a buffer provided in the original peripheral device, a memory on the control device side, or a temporary storage device other than the semiconductor memory. The control means only needs to control the data accumulation speed with reference to the substantial accumulated data amount in the buffer means. The amount of data stored in the buffer means is a substantial amount of data that has not been read, and does not always match the amount of data stored. Further, it is not necessary to refer to a strict data amount, and the data amount may be roughly detected. Further, it may be another data that substantially matches the data amount.

The data storage speed is controlled so that the substantial stored data amount of the buffer means does not overflow. Generally, the data reproduction speed is changed to adjust the speed of the stored data amount. In other words, the reproduction speed may be changed linearly, or if the reproduction means can reproduce and stop the data, the reproduction and stop may be repeated to change the speed. The difference between the data amount to be read and the data amount to be reproduced is the accumulation speed, and any data that affects this speed may be used. In controlling such inversely proportional speed,
The speed may be sequentially changed to change the speed, or the speed may be instructed to be inversely proportional to hardware.

According to a second aspect of the present invention, a first aspect is provided.
In the data reproducing device described in the above, the reproducing means, a rotating storage medium, a reproducing speed changing unit capable of changing the data reproducing speed by changing the rotational speed of the rotating storage medium according to control from the control means, Is provided. According to the invention having such a configuration, the rotating drive unit that mechanically drives the storage medium or the like to rotate is provided, and the reproducing speed changing unit changes the rotating speed of the rotating drive unit according to control from the control unit. Thus, the data reproduction speed is changed.

A motor or the like that is driven to rotate is not limited to a case where the storage medium itself is driven to rotate, and may be a disk-shaped storage medium or a magnetic tape. .

According to a third aspect of the present invention, in the data reproducing apparatus according to the first or second aspect, the control means outputs a clock signal having a predetermined cycle corresponding to a data accumulation speed. And the reproducing means includes a clock synchronous reproducing unit for reproducing at a speed corresponding to the cycle of the clock signal.

According to the invention having such a configuration, the control means outputs a clock signal of a predetermined cycle corresponding to the data accumulation speed by the clock oscillating unit, and the reproducing means outputs the clock signal by the clock synchronous reproducing unit. Since data is reproduced at a speed corresponding to the cycle of the clock signal, data is reproduced at a data reproduction speed corresponding to the data accumulation speed as a result. In reproducing data according to the cycle of the clock signal, the data may be reproduced at a speed corresponding to the average frequency at that time, or one operation may be performed every clock or several clocks to reproduce the data. You can do it.

As an example of changing the period of the clock signal,
According to a fourth aspect of the present invention, in the data reproducing apparatus according to the third aspect, the clock control section controls the data accumulation speed by thinning out the clock signal. According to the invention having such a configuration, the clock control unit controls the data accumulation speed by thinning out the clock signal like a frequency divider. As for the thinning out of the clock signal, the frequency may be divided, or the gate may be formed as necessary to completely cut off the clock signal, and as a result, the thinning out may be performed.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a main part of a CD-ROM reproducing apparatus to which a data reproducing apparatus according to an embodiment of the present invention is applied. In FIG. 1, a host computer 10 is connected to a CD-ROM playback device 20, and the host computer 10 transmits a CD-ROM.
A request to reproduce data is issued to the ROM reproducing device 20 to read data. In this sense, in the present embodiment, the host computer 10 corresponds to a reading device. In this example, reading from an external device is performed. However, the reading device may be an external device or an internal device with respect to the data reproducing device.

The CD-ROM playback device 20 is a CD-RO
A reproducing mechanism 21 for reproducing M and outputting an EFM (Eight to Fourteen Modulation) signal; a demodulating process and an error correcting process for the EFM signal to convert the EFM signal into original digital data; And a demodulation control unit 22 that outputs the drive control signal of More specifically, the drive control signal is transmitted from a spindle motor for rotating the CD-ROM in the reproducing mechanism 21 or an optical pickup to the CD-RO.
These are a pickup feed motor for moving in the M tracking direction, a servo motor for tracking and focusing of the objective lens, and other servo signals required for data reproduction.

The demodulation control unit 22 receives the system clock signal Sc and receives the system clock signal Sc.
, The rotational speed of the spindle motor is controlled. Similarly, the EFM signal is also processed based on the same system clock signal Sc. As a result, while the rotation speed is controlled by the same system clock signal Sc, the demodulation of data is also performed in synchronization with the desired speed. Data can be reproduced. That is, in the present embodiment,
The reproducing mechanism section 21 and the demodulation control section 22 constitute a reproducing section. Therefore, the data storage medium corresponds to a CD-ROM as a rotating medium, and data can be reproduced at a desired speed according to the system clock signal Sc.

The demodulation control section 22 processes the EFM signal and returns the digital data to a buffer memory section 23.
Of the buffer memory 2 under the control of the memory controller 23b.
3a is temporarily stored. That is, the memory controller 23b writes and reads the reproduced data to and from the buffer memory 23a, and manages the data. The reproduced data output from the demodulation control unit 22 is stored in the buffer memory 23a. While writing, in response to a read request from the host computer 10,
The same data is read and output. That is, the memory controller 23b writes and reads data by designating an address of the buffer memory 23a, and realizes a function as a buffer using a predetermined address space. Therefore, in the present embodiment, the memory controller 23b and the buffer memory 23a constitute buffer means.

In realizing the buffer function, the memory controller 23b manages a data write address Aw and a data read address Ar at each time with respect to the buffer memory 23a, and outputs the data write address Aw to the arithmetic unit 24a of the reproduction control unit 24. ing. The calculation unit 24a calculates Aw-Ar = Db (2) in order to obtain the data accumulation amount Db in the buffer memory 23a, and outputs the accumulation amount Db to the clock control unit 24b.

The clock control unit 24b outputs a control voltage of the VCO 24c in order to adjust the data reproduction speed from the data accumulation amount Db calculated by the calculation unit 24a. The VCO 24c corresponds to the control voltage. A periodic system clock signal Sc is generated. As described above, the system clock signal Sc changes the data reproduction speed, and the reproduction speed is changed based on the data accumulation amount Db only in the buffer memory 23.
This is to prevent a from overflowing. To do this, the accumulated amount Db is stored in the buffer memory 23.
It is necessary to reduce the data reproducing speed when the maximum storage capacity Lb approaches the maximum storage capacity Lb. The clock control section 24b adjusts the cycle of the system clock signal Sc to adjust the cycle of the system clock signal Sc so as to achieve such a relationship. Output the control voltage.

In order to prevent the buffer memory 23a from overflowing, the buffer memory 23a
The data reproduction speed is set such that the data reproduction is performed at a high speed until the data storage amount Db reaches a predetermined amount, and the data reproduction speed is kept constant after the data storage amount Db exceeds the predetermined amount. May be controlled, or various correspondences may be made, such as simply changing the data reproduction speed in inverse proportion to the data accumulation amount Db.

That is, in the present embodiment, the reproduction control section 24 constitutes a reproduction means, and the accumulated amount Db, which is the difference between the data write address Aw and the data read address Ar, is substantially equal to the data stored in the buffer memory 23a. Buffer memory 23a
The data playback speed is changed so as not to overflow. In the present embodiment, since the data reproduction speed matches the data accumulation speed, the data accumulation speed is controlled by changing the data reproduction speed.

The rotation speed of the spindle motor is controlled by controlling the system clock signal Sc. The arithmetic unit 24a calculates Lb- (Aw-Ar) = Lb-Db (3) It is also possible to perform the following calculation to directly control the rotation speed of the spindle motor.

Next, the operation of the present embodiment having the above configuration will be described with reference to FIG. Here, FIG.
Shows the operation of the CD-ROM playback device 20, and FIG.
Represents the data reproduction speed Sr, and FIG. 4C shows the operation of the host computer 10.

At time t21, it is assumed that the host computer 10 outputs a data read request to the CD-ROM reproducing device 20, and the CD-ROM reproducing device 20 starts operating. Then, as shown in FIG.
The OM playback device 20 immediately starts the search state S at the same time t21.
, And enters the data reproduction state P at time t22. At this time, data reproduction is performed at high speed until time t24 when the data accumulation amount Db of the buffer memory 23a reaches a predetermined value, as shown in FIG. Gradually decelerate so as to converge. Until the time t25 at which the reproduction of all data is completed, the search is continuously performed without entering the search state S on the way.

On the other hand, the host computer 10 operates at time t.
21, the state becomes the waiting state W, and the time t2 after the time t22
3, the data read state R from the buffer memory 23a
Becomes Then, the host computer 10 can continuously read the data without entering the waiting state W until the time t26 when the reading of the data stored in the buffer memory 23a ends.

Even if the host computer 10 reads data of a long data length,
It is not necessary to reduce the reproduction speed Sr of the initial data.
Therefore, data reproduction can be started earlier than before. That is, the data reading start time t23 of the host computer 10 is advanced earlier without the CD-ROM reproducing device 20 being in the search state S on the way, so that the time until the data reading end time t26 is shorter than in the conventional case. I'm done.

As described above, the reproducing means including the reproducing mechanism unit 21 and the demodulation control unit 22 provides the system clock signal Sc
The data can be reproduced at a reproduction speed corresponding to the data, and the reproduced data is temporarily stored in the buffer memory 23a constituting the buffer means and read out from the host computer 10. The memory controller 23b constituting the same buffer means manages the data write address Aw and the data read address Ar at each time with respect to the buffer memory 23a, and the arithmetic section 24a of the reproduction control section 24 constituting the reproduction means. Calculates the data accumulation amount Db from this difference, and the clock control unit 24b adjusts the system clock signal S to change the data reproduction speed so that the buffer memory 23a does not overflow.
The control voltage of the VCO 24c that outputs c is determined and output.

[0035]

As described above, according to the present invention, the reproduction of data is started without performing an operation first, so that no extra time is required. Since the reproduction is started at a normal speed, the search time is shortened. It is possible to provide a data reproducing device that can achieve higher speed. Of course, there is no buffer overflow. Until the amount of data stored in the buffer memory reaches a predetermined amount, data can be reproduced from the optical disk at high speed and stored in the buffer memory.

According to the second aspect of the present invention, since the rotation speed of the rotary drive unit is changed, the speed can be controlled relatively easily.

Further, according to the third aspect of the present invention,
The clock signal controls the reproduction speed, and only the cycle is changed, so that the configuration can be simplified.

Further, according to the invention of claim 4,
Since only the clock signal is thinned out, the configuration can be simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram of a CD-ROM playback device to which a data playback device according to an embodiment of the present invention is applied.

FIG. 2 is a diagram for explaining an operation state of the data reproducing apparatus.

FIG. 3 is a diagram showing the amount of data stored in a buffer memory when there is a difference between a reading speed and a reproducing speed.

FIG. 4 is a CD-ROM to which a conventional data reproducing apparatus is applied.
It is a block diagram of a reproducing device.

FIG. 5 is a diagram for explaining an operation state of a conventional data reproducing apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 host computer 20 CD-ROM playback device 21 playback mechanism unit 22 demodulation control unit 23 buffer memory unit 23a buffer memory 23b memory controller 24 playback control unit 24a operation unit 24b clock control unit 24c VCO

Claims (4)

[Claims] 1. A reproducing means for reproducing data from a data storage medium at a desired speed, and interposed between a reading device and the reproducing device for temporarily storing reproduced data and reading from the reading device. Possible buffer means, and control means for controlling the data accumulation speed from the reproducing means with reference to the substantial accumulated data amount in the buffer means so that the buffer means does not overflow. Data playback device. 2. A data reproducing apparatus according to claim 1, wherein said reproducing means changes a rotational speed of said rotary drive section and a rotational speed of said rotary drive section in accordance with control from said control means. A data reproduction device comprising: a reproduction speed changing unit that can change the data reproduction speed. 3. The data reproducing apparatus according to claim 1, wherein said control means has a clock oscillating section for outputting a clock signal of a predetermined cycle corresponding to said data accumulation speed, and said reproducing means. Is a data reproducing apparatus having a clock synchronous reproducing section for reproducing at a speed corresponding to a cycle of the clock signal. 4. The data reproducing apparatus according to claim 3, wherein the clock control section controls the reproduction speed by thinning out the clock signal.