JPH09222957A - Disk access device and video-on-demand device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate futile time and to improve response to an external device by making a schedule according to the number of terminal devices in a connection state or the number of access request signals. SOLUTION: As a cycle for a case wherein external devices 1-4 are all connected in advance, a cycle TP which is a time wherein requests from all the external devices can be processed is set in a timer 7 by a cycle time control means 12. Then, when the number of external devices in the connection state which is obtained from a connection monitor device 11 is equal to the total number 4 of the external devices, the cycle TP is outputted as it is to a scheduling device 6. When the number of external devices in the connection state is less than the total number of the external device, a value obtained by shortening the cycle TP is outputted to the scheduling device 6. The scheduling device 6 changes access order at every cycle time determined by the cycle time control means 12 according to data positions of respective requests on a disk so that disk access is made fast.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video-on-demand device that provides video information in response to a request from a user, and in particular, scheduling is performed at a fixed cycle when data is read from a disk device by a plurality of requests. The present invention relates to a disk access device for performing.

[0002]

2. Description of the Related Art FIG. 10 is a block diagram showing an example of the configuration of a conventional general disk access device. In the figure, access requests from the four external devices 1 to 4 are stored in a FIFO memory 5 which is a request receiving memory. The scheduling device 6 optimizes the access request sequence for each cycle time of the timer 7 in order to efficiently read the data, and writes the access request in the FIFO memory 8 which is the request service memory. The disk control device 9 that performs processing for reading data from the disk device 10
Access is performed in the order of requests stored in the FIFO memory 8. As a result, the disk controller 9 reads data in a time division manner in response to requests from the four external devices 1 to 4. The cycle time supplied by the timer 7 is set to the time from the disk device 10 until the reading of data according to the requests of all four external devices 1 to 4 is completed.

The operation of the disk access device configured as described above will be described with reference to FIGS. 11, 12 and 13. FIG. 11 is a diagram showing a flow of a request when changing from an arbitrary cycle N to a cycle N + 1 depending on the cycle time of the timer 7. Four requests R1 stored in the FIFO memory 5
The processing order of R4 to R4 is R2 → R4 → R1 → R3, but normally it is necessary to change the order according to the position on the disk so that the disk access becomes faster. Therefore, at the same time when the cycle N ends, the scheduling device 6 fetches four requests and changes the order so that the disk access speed is increased. Then, in the cycle N + 1, the requests arranged in the order for actual service are placed in the FIFO memory 8 To store. In this way, the disk device 10 (FIG. 10) is accessed according to the request order R1 → R2 → R3 → R4 stored in the FIFO memory 8.

Although FIG. 11 shows the flow of requests, FIG.
FIG. 9 is a diagram showing a relationship between a request and a data read time in a cycle N when the cycle time supplied by the timer 7 is TP. As in the case of FIG. 11, the four requests R1 to R4 are subjected to scheduling processing by the scheduling device 6 when the cycle N ends, and the processing in the FIFO memory 8 is executed at high speed by the scheduling device 6 and the actual data The processing time is so short that it can be ignored compared to the cycle time which is the read time. Therefore, it is not shown in FIG. In FIG. 12, the FIFO with the cycle N
The upper part shows the request accepted by the memory 5, and the lower part shows how the FIFO memory 8 actually reads the data in a time division manner. From FIG. 12, the time from the reception of a request to the actual reading of data is TP / 4 at the minimum and 7/4 TP at the maximum (for example, R in the case of FIG. 12).
It can be seen that 4) is required, and on average only the cycle time TP is required. In addition, the cycle time T until the next request
You need to wait for P.

Similar to FIG. 12, FIG. 13 is a diagram showing the relationship between the request and the data read time, but shows the case where there are only two requests (R4 and R2). Thus, even when there are only two requests, the time from the request to the data reading is fixed by the cycle time TP, and the request from each external device is made every cycle time TP.

FIG. 14 is a block diagram showing an example of the configuration of a conventional general video-on-demand apparatus. In the figure, a storage device 100 that stores video data is connected to a data transmission device 110.
Four terminal devices 131 to 134 are connected via ten to four buffer memories 121 to 124, respectively. The request control device 240 uses the terminal devices 131 to 134.
Receiving a distribution request from the storage device 100, the data is read from the storage device 100 in a time-division manner in response to each request,
By controlling 0, data is written in the buffer memories 121 to 124.

The operation of the conventional video-on-demand system configured as described above will be described with reference to FIGS. 14 to 16. FIG. 15 shows the length relationship between the data stored in the storage device 100 (FIG. 14) and written in the buffer memories 121 to 124 (FIG. 14) and the data processed in each terminal device 131 to 134 (FIG. 14). FIG.
The data stored in the storage device 100 requires a time of 1 TS before being read from the data and written in the buffer memories 121 to 124 via the data transmission device 110. This data is displayed in each terminal device 131-134 while decompressing, taking 1 TP time. At this time, the number of terminal devices is four, and the data transmission device 110 has four.
Since data is written to the buffer memories 121 to 124 in a time division manner, 1TP = 4TS. So 1
TP is the cycle time of this device.

FIG. 16 is a diagram showing how data is read out at each cycle time with the horizontal axis of the figure as time.
As shown in FIG. 15, the time required to read from one terminal device is 1TS, and the cycle time in the four terminal devices is 1TP. During 1TS,
From the disk device 100 to the buffer memories 121 to 124
Data is written to any one of them. Therefore, 4
During the TS, data is written in the four buffer memories 121 to 124, and the written data is displayed by the terminal device connected to each of them for 4 TS (= 1 TP) time. The state of the terminal device 132 at this time is shown in FIG.
It is shown in the bottom row. That is, the buffer memory 122
By taking two areas to be written in and alternately using them, the display (hatched portion) on the terminal device 132 is not interrupted. Such a video-on-demand device
JP-A-2-197914 (Japanese Patent Publication No. 6-1430)
No.). In such a video-on-demand device, a disk device is usually used as the storage device 100, and thus the disk access device as described above is used as the request control device 240. Therefore, the time interval at which the terminal devices 131 to 134 request data is fixed to the cycle time 1TP depending on the number of terminal devices.

[0009]

In the prior art as described above, all the external devices 1 to 4 (or the terminal device 13).
1 to 134), there is a problem in that the cycle time determined by the total number of external devices (or the total number of terminal devices) does not change even when there is no request, and there is a large amount of wasted time during which processing is not performed. .

In view of the above problems, it is an object of the present invention to provide a disk access device and a video-on-demand device which eliminate wasteful time during which processing is not performed and improve responsiveness to an external device (or terminal device). To do.

[0011]

DISCLOSURE OF THE INVENTION The disk access device of the present invention, when all the external devices are in the connected state,
When the cycle time T0 determined by the total number of external devices is output to the scheduling device and the number of connected external devices or the number of access request signals is less than the total number,
A cycle time control means for outputting a cycle time T1 shorter than the cycle time T0 to the scheduling device is provided. Thus,
The cycle for receiving an access request from an external device is shortened, and the responsiveness can be improved. The video-on-demand apparatus of the present invention is a disk access apparatus that operates a disk apparatus according to an access request signal that is scheduled at each cycle time that is changed according to the number of connected terminal apparatuses or the number of access request signals. The disk access device is provided with means for reading data from the storage device that stores the video data. The terminal device displays the read data while expanding the read data over a certain period of time. In this way, data can be read out without wasting time within the cycle time, so that the cycle for accepting an access request from the terminal device can be shortened and responsiveness can be improved.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A disk access device of the present invention is in a connected state by monitoring a request receiving memory for storing access request signals from a plurality of external devices and whether or not the external device is in a connected state. A connection monitoring device that detects the number m of external devices, a scheduling device that reads the access request signal stored in the request reception memory at every cycle time and changes the access order, and a request service memory that stores the output from the scheduling device. And a disk controller which operates the disk device according to the access request signal stored in the request service memory, and when the above-mentioned number m is input and all the external devices are in the connected state, it is determined by the total number of external devices. Output the periodic time T0 to the scheduling device, and if the number m is less than the total number of external devices, And a cycle time control means for outputting a periodic time T1 shorter than the time T0 to the scheduling apparatus.

Further, instead of the configuration of providing a connection monitoring device to detect the number of external devices in a connected state, the number m of access request signals stored in the request reception memory is monitored, and this number m is an external device. If the number m is less than the total number of external devices, the cycle time T0 determined by the total number of external devices is output to the scheduling device. A cycle time control means for outputting the short cycle time T1 to the scheduling device may be provided.

When the total number of the external devices is k, the cycle time T1 may have a relationship of T1 = (m / k) · T0.

The video-on-demand apparatus of the present invention expands and displays compressed video data and outputs a request signal for access to obtain desired video data. A disk access device that monitors whether or not there is a disk access device that operates a disk device according to an access request signal that is scheduled at each cycle time that is changed according to the number of connected terminal devices, and is controlled by the disk access device. A data sending and buffer means for writing the video data read from the storage device by the disk access device to the buffer memory, the storage device storing the video data and the buffer memory connected to each terminal device. Prepare

Another video-on-demand device of the present invention is
Instead of the disk access device of the video-on-demand device, a disk access device that operates a disk device according to an access request signal that is scheduled at each cycle time changed according to the number of access request signals given from a terminal device. Equipped with.

[0017]

Embodiments of the present invention will be described with reference to the drawings. << Embodiment 1 >> FIG. 1 is a block diagram showing the configuration of a disk access device according to the first embodiment. The disk access device 140 includes a connection monitoring device 11, a FIFO memory 5 as a request receiving memory, and a scheduling device 6.
A FIFO memory 8 as a requested service memory, a disk controller 9, a timer 7 for supplying a cycle time,
It is composed of the cycle time control means 12 and is connected to the external devices 1 to 4 and the disk device 10. . The connection monitoring device 11 constantly monitors whether or not the external devices 1 to 4 are in a connected state. Access requests from the external devices 1 to 4 are stored in the FIFO memory 5. The scheduling device 6 reads the requests stored in the FIFO memory 5 at each cycle time determined by the cycle time control means 12, and the access order is adjusted according to the data position on the disk of each request so that the disk access becomes fast. Are replaced and stored in the FIFO memory 8. The disk controller 9 operates the disk device 10 in accordance with the request stored in the FIFO memory 8 to read the data from the external devices 1 to 4 in a time-divisional manner and the cycle time control means 1
2 within the cycle time.

As the cycle time when all the external devices 1 to 4 are connected in advance to the cycle time control means 12, the timer 7 is provided with a cycle time TP which is a time during which requests from all external devices can be processed. Set it. Then, when the number of connected external devices obtained from the connection monitoring device 11 is equal to the total number of external devices, which is 4, the cycle time TP is output to the scheduling device 6 as it is. When the number of connected external devices is less than the total number of external devices, a value obtained by shortening the cycle time TP is output to the scheduling device 6. The value obtained by shortening the cycle time TP is a value given by (m / k) · TP, where k is the total number of external devices and m is the number of external devices in the connected state (the number of connections). That is, when the number of connections is 2, TP is 1 /
The value is set to 2, and when the number of connections is 1, the value is set to 1/4 of TP. This is because the cycle time TP is set as the time for reading data from the four external devices 1 to 4, so that when the number of connected external devices is two, it is 1 /
This is because the data can be read in 2 times and the data can be read in 1/4 of the time in one case.

FIG. 2 is a diagram showing the flow of requests when the number of connections of external devices is two in the first embodiment. R in the FIFO memory 5 and the FIFO memory 8 in FIG.
2 and R4 indicate the requirements of the external devices 2 and 4 (FIG. 1), respectively. The FIFO memory in the figure is such that the lowermost one is a request received earlier, the processing is performed first, and the next request is stacked on top. Therefore,
The requests stored in the FIFO memory 8 are processed in the disk device 10 (FIG. 1) in the order of R2 → R4.

In FIG. 2, since the number of connected external devices is 2, the number of requests stored in the FIFO memory 5 during the period N is two (R2 and R4). Further, the cycle time control means 12 which has received the signal indicating that the number of connections is 2 from the connection monitoring apparatus 11 reduces the value of the cycle time TP initially set in the timer 7 to ½, and the scheduling apparatus 6
To supply. Then, in the cycle N + 1, the scheduling device 6 fetches the request of the FIFO memory 5, changes the order according to the position on the disk so that the disk access becomes fast, and then stores it in the FIFO memory 8. In this example, the request that was R4 → R2 is changed to R2 → R4.
Are replaced in the order of. In this way, the external devices 2 and 4
Is processed at a cycle of 1/2 of the value TP set in the timer 7, and the cycle time does not change until the connection monitoring device 11 detects a change in the number of connections.

FIG. 3 is a diagram showing the relationship between the request and the data read time when the number of connections of external devices is 2 in the first embodiment. In the cycle N, the connection monitoring device 11 detects that the number of connections of the external devices 1 to 4 is 2, and processes the requests R4 and R1. The state of storage in the FIFO memory 5 with the time axis as the horizontal axis. In the upper part of the figure, the data stored in the FIFO memory 8 is read by the disk controller 9 in a time division manner. Here, as in the case of FIG. 2, the requests R1 and R4 have the cycle N ended and the cycle N +.
When it becomes 1, the processing is performed by the scheduling device 6 and the FIFO memory 8, and the scheduling process inside the scheduling device 6 and the FIFO memory 8 are performed.
The storage in is executed in a very short time that can be ignored as compared with the actual data read time, so it is not shown.

In FIG. 3, when the cycle is N, the connection monitoring device 11
Detects that the number of connections of external devices is 2, the cycle time control means 12 changes the cycle time from the cycle N + 1 to 1/2 of the value TP initially set in the timer 7.
Therefore, for example, the time until the request accepted in the cycle N + 1 is executed is always TP or less, and the external device 4
The request interval from is TP / 2. Furthermore, the cycle N + 1
After that, it can be seen that the data reading time is not wasted.

<< Second Embodiment >> Next, a second embodiment will be described. FIG. 4 is a block diagram showing the configuration of a disk access device according to the second embodiment of the present invention. The disk access device 140 includes a FIFO memory 5 that is a request reception memory, a scheduling device 6, a FIFO memory 8 that is a request service memory, and a disk control device 9.
And a timer 7 for supplying a cycle time, and a cycle time control means 13, which are connected to the external devices 1 to 4 and the disk device 10. External devices 1 to 4, FI
FO memory 5, scheduling device 6, timer 7, F
IFO memory 8, disk control device 9, disk device 1
For 0, the same operation as in the first embodiment is performed. The cycle time control means 13 constantly monitors the number of requests stored in the FIFO memory 5, and when the number of requests is equal to the total number of external devices, 4, the cycle time TP is used as it is.
When the number of requests is less than the total number of external devices, a value obtained by shortening the cycle time TP is output to the scheduling device 6
Output to The value obtained by shortening the cycle time TP means that TP is 1/2 when the number of requests is 2 as in the case of the first embodiment.
If the number of requests is 1, TP is set to 1/4.

FIG. 5 shows the external devices 1 to 4 in the second embodiment.
It is a figure showing the flow of a request when the number of requests from is 2. R1 and R4 in the FIFO memory 5 and the FIFO memory 8 in FIG. 5 indicate requests from the external device 1 and the external device 4, respectively. The FIFO memory in the figure is the same as that in the first embodiment, and the requests stored in the FIFO memory 8 are the disk device 10 in the order of R1 → R4.
The processing in (FIG. 4) is executed. In FIG. 5, the number of requests from the external device is 2, and during the period N, F
There are two requests stored in the IFO memory 5. This F
Cycle time control means 13 for monitoring the IFO memory 5
Detects that the number of requests is 2, reduces the value of TP initialized in the timer 7 to 1/2, and supplies the value to the scheduling device 6. Then, in the cycle N + 1, the scheduling device 6 fetches the request of the FIFO memory 5, changes the order according to the position on the disk so that the disk access becomes fast, and then stores the request in the FIFO memory 8. In this example, the request which was R4 → R1 is changed to R1 →
The order is R4. In this way, the request from the external device is processed in a cycle of ½ of the value TP set in the timer 7, and the cycle time control means 13 detects the change in the number of requests within the cycle. Does not change.

FIG. 3 is a diagram showing the relationship between the request and the data read time when the number of connections of the external device is two in the first embodiment. If the request R2 in FIG. In the second embodiment of the invention, there is a relationship between the request and the data read time when the number of requests within the cycle time is 2. The cycle time control means 13, which has detected that the number of requests is 2 in the cycle N, changes the cycle time from the cycle N + 1 to ½ of the value TP initially set in the timer 7. for that reason,
For example, the time until the request received in the cycle N + 1 is executed is TP or less, and the request interval from the external device 4 is TP / 2. Furthermore, in the cycle N + 1 and later,
It can be seen that the data reading time is not wasted. These operations are similar to those in the first embodiment. As described above, the second embodiment differs from the first embodiment only in the operation reference when the cycle time control unit 13 shortens the cycle time.

<< Third Embodiment >> Next, a third embodiment will be described. FIG. 6 is a block diagram showing the configuration of the video on demand device. The device is a disk access device 140, a disk device 100, and a data transmission device 11.
0, the buffer memories 121 to 124, and the terminal device 13
1-134. The internal configuration of the disk access device 140 is substantially the same as that of the disk access device 140 of the first embodiment shown in FIG. 1, and the same reference numerals are given to each component. The request reception memory 5 is the FIFO memory 5 of FIG. 1, and the request service memory 8 is the F memory of FIG.
Each corresponds to the IFO memory 8. The operation of each of these elements is as described in the first embodiment. The terminal devices 131 to 134 correspond to the external devices 1 to 4 of FIG. 1, and the disk device 100 corresponds to the disk device 10 of FIG.

Next, the operation of the video-on-demand device will be described. First, the terminal devices 131 to 134 issue a distribution request to the disk access device 140. Compressed video data is stored in the disk device 100, and the data read by the disk access device 140 is stored in the buffer memory connected to each terminal device 131 to 134 via the data transmission device 110. 1
21 to 124 are written. Terminal devices 131 to 134
Displays while expanding the data in these buffer memories 121 to 124 over a certain period of time.

The data stored in the disk device 100 is compressed video data and has a normal cycle time TP.
If it is, the data length is as shown in FIG. That is, it takes 1 TS to read from the disk device 100 and write to the buffer memories 121 to 124 via the data transmission device 110. This data is displayed in each terminal device 131-134 while decompressing, taking 1 TP time. In the case of FIG. 6, the number of terminal devices is four.
Since the data transmission device 110 writes data to four buffer memories in a time division manner, 1TP = 4TS
Becomes Therefore, 1TP is the cycle time of this device.

In FIG. 7, the number of connected terminals is 2 in the third embodiment.
In the case of, a diagram showing a temporal length relationship between data read from the disk device 100 and written in two of the buffer memories 121 to 124 and data processed in the terminal device. In this case, as described in the first embodiment, since the cycle time in the disk access device 140 changes to TP / 2, the writing time to the buffer memory and the reproduction time in the terminal device are also shown in FIG. 1 / each compared to the one (corresponding to the broken line in FIG. 7)
2, and the amount of read data is also halved.

FIG. 8 shows how data is read at each cycle time in the third embodiment with the horizontal axis of the drawing as time, and connection is made at the cycle N as in the first embodiment shown in FIG. The number of terminals becomes 2, and the cycle after cycle N + 1 is
It is TP / 2. The upper part of FIG. 8 shows the timing at which the disk access device 140 writes data from the disk device 100 in a time-sharing manner. Areas 131 and 132 in the drawing write data to the buffer memories 121 and 122 for the terminal devices 131 and 132, respectively. Is shown. The lower part shows how data is written to the buffer memory 122 and displayed on the data terminal device 132 which displays while expanding.

According to FIG. 8, in the cycle N where the cycle time is TP, the data written in 1 TS as shown in FIG. 15 is reproduced in 4 TS, that is, 1 TP. Cycle N + when cycle time becomes TP / 2
From 1 onward, the read data amount is halved, and the write time is set to TS / 2 as shown in FIG. 7, so that the reproduction time is also set to TP / 2. Buffer memory 1
By taking two areas to be written in 22 and using them alternately, in the third embodiment, the display in each terminal device is not interrupted. It can be seen from FIG. 8 that the distribution requests from the terminal devices 131 and 132 can be executed for each TP / 2. Further, the data writing time assigned to each terminal device is 1 TS, which is the same as when the cycle time is TP, even if the cycle time is shortened to TP / 2. Therefore, it is possible to double the reproduction data per unit time in each terminal device by setting the writing time to the buffer memory 122 to 1TS instead of TS / 2 as shown in FIGS. It is possible, and the double speed reproduction can be performed with the amount of the buffer memory unchanged.

<< Fourth Embodiment >> Next, a fourth embodiment will be described. FIG. 9 is a block diagram showing the configuration of the video on demand device according to the fourth embodiment of the present invention. The device is a disk access device 140 and a disk device 10.
0, the data transmission device 110, and the buffer memory 121
To 124 and terminal devices 131 to 134. The internal configuration of the disk access device 140 is shown in FIG.
The disk access device 140 is substantially the same as the disk access device 140 of the second embodiment shown in FIG.
The request receiving memory 5 corresponds to the FIFO memory 5 of FIG. 4, and the request service memory 8 corresponds to the FIFO memory 8 of FIG. The operation of each of these elements is as described in the second embodiment. The parts other than the disk access device 140 are the same as the configuration of the third embodiment.

The data stored in the disk device 100, the data written in the buffer memories 121 to 124, and the time for displaying while decompressing in each of the terminal devices 131 to 134 are the same as those in the third embodiment. Only the reference of the operation when the cycle time control means 13 shortens the cycle time is different. This is as described in Example 2. The reading of data for each cycle time is the same as that described with reference to FIG. 8 in the third embodiment, and in the fourth embodiment, the display in each terminal device is not interrupted. Further, as in the case of the third embodiment, it is possible to double the reproduction data per unit time in each terminal device, and it is possible to perform double speed reproduction with the amount of buffer memory unchanged.

In Examples 1 to 4, external devices 1 to 4
(Or the number of terminal devices 131 to 134) is four,
This is an example. As this number increases, the effect of improving responsiveness becomes relatively greater. Especially when the number is several tens, the effect is remarkable. In the first to fourth embodiments, the request receiving memory 5 and the request service memory 8 are configured by the FIFO memory, but the present invention is not limited to this, and may be any one that can store the order of the request contents correctly. Further, the request receiving memory 5 and the request service memory 8 may be physically the same memory, and the areas may be divided and used. Examples 1-4
In the above, the scheduling device 6 changes the access order according to the data position on the disk of each request so that the disk access becomes fast. However, the data reading of all requests from the disk device 10 (100) within the cycle time is performed. If the processing is completed, it is not necessary to change the access order, and in this case, the requests stored in the request reception memory 5 are collected every set cycle time, and the requests are passed to the request service memory 8. Just good.

[0035]

The present invention has the following effects.

The disk access device of the present invention is provided with a connection monitoring device for detecting the number of external devices in the connected state, and when all the external devices are in the connected state, a cycle determined by the total number of the external devices. Since the cycle time control means for outputting the time T0 to the scheduling apparatus and outputting the cycle time T1 shorter than the cycle time T0 to the scheduling apparatus when the number of connected external apparatuses is less than the total number is provided, The operation cycle time of the scheduling device can be shortened according to the connection state. Therefore, the cycle for accepting requests from external devices is shortened,
It is possible to improve responsiveness. When the external device (and the terminal device) is connected through a switching network such as a telephone line, the connection monitoring device can be realized by the switching device, and thus the configuration can be provided very easily.

Further, the disk access device having another configuration monitors the number of access request signals given from the external device and stored in the request reception memory, and if the number is equal to the total number of external devices, it is determined by the total number. Cycle time T
When the number 0 is output to the scheduling device and the number is smaller than the total number of external devices, the cycle time control means for outputting the cycle time T1 shorter than the cycle time T0 to the scheduling device is provided. Accordingly, the operation cycle time of the scheduling device can be shortened. Therefore, the cycle of receiving the request from the external device is shortened, and the responsiveness can be improved.

The video-on-demand apparatus of the present invention monitors whether or not the terminal device is in the connected state, and performs an access request scheduled for each cycle time that is changed according to the number of the connected terminal devices. Since the disk access device for operating the disk device according to the signal is provided, and the video data is read from the storage device by the disk access device and the video data is expanded and displayed by the terminal device, the terminal device is connected. Accordingly, the operation cycle time of scheduling can be shortened. Therefore, the period for receiving the request from the terminal device is shortened, and the responsiveness can be improved. Also,
By having such a configuration, if the writing time to the buffer memory is not shortened even if the cycle time is shortened, the reproduction data per unit time in the terminal device is doubled. It is also possible to perform double speed reproduction or the like in the terminal device without increasing the amount of buffer memory.

The video-on-demand apparatus having another configuration performs scheduling at each cycle time which is changed according to the number of access request signals given from the terminal apparatus, instead of the disk access apparatus of the above-mentioned video-on-demand apparatus. Since the disk access device for operating the disk device according to the access request signal is provided, the same effect as that of the video-on-demand device can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a disk access device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a request flow when the number of external device connections is 2 in the first embodiment.

FIG. 3 is a diagram showing a relationship between a request and a data read time when the number of connections of external devices is 2 in the first embodiment.

FIG. 4 is a block diagram of a disk access device according to a second embodiment.

FIG. 5 shows that the number of requests from an external device is 2 in the second embodiment.
It is the figure which showed the flow of the request in the case of.

FIG. 6 is a block diagram of a video-on-demand device according to a third embodiment.

FIG. 7 is a diagram showing a time length relationship between data stored in the buffer memory and data displayed on the terminal device when the number of connected terminal devices is 2 in the third embodiment. .

FIG. 8 is a diagram showing how data is read at each cycle time in the third embodiment.

FIG. 9 is a block diagram of a video-on-demand device according to a fourth embodiment.

FIG. 10 is a block diagram showing a conventional disk access device.

FIG. 11 is a diagram showing a request flow in a conventional disk access device.

FIG. 12 is a diagram showing a relationship between a request and a data read time in a conventional disk access device.

FIG. 13 is a diagram showing a relationship between a request and a data read time when the number of requests is 2 in the conventional disk access device.

FIG. 14 is a block diagram showing a conventional video on demand device.

FIG. 15 is a diagram showing the relationship between the length of time between the data stored in the buffer memory and the data displayed on the terminal device in the conventional video on demand device.

FIG. 16 is a diagram showing how data is read every cycle time in the conventional video-on-demand apparatus.

[Explanation of symbols]

 1-4 external device 5 FIFO memory (request reception memory) 6 scheduling device 7 timer 8 FIFO memory (request service memory) 9 disk control device 10 disk device 11 connection monitoring device 12, 13 cycle time control means 100 disk device 110 data transmission Device 121-124 Buffer memory 131-134 Terminal device

Claims (5)

[Claims] 1. A request reception memory for storing access request signals from a plurality of external devices, and a connection for monitoring whether or not the external devices are in a connected state and detecting the number m of the external devices in the connected state. A monitoring device, a scheduling device that reads an access request signal stored in the request reception memory at every cycle time and changes the access order, a request service memory that stores an output from the scheduling device, and a request service memory. A disk controller that operates a disk device according to a stored access request signal, and a cycle time T0 determined by the total number of external devices when the number m is input and all of the external devices are in a connected state. To the scheduling device, and when the number m is less than the total number of external devices, the Disk access device and a cycle time control means for outputting a periodic time T1 shorter than the time T0 to the scheduling device. 2. A request reception memory for storing access request signals from a plurality of external devices, a scheduling device for reading access request signals stored in the request reception memory at every cycle time, and changing the access order, A request service memory for storing an output from the scheduling device, a disk controller for operating a disk device according to an access request signal stored in the request service memory, and a number m of access request signals stored in the request receiving memory. If it is the same as the total number of the external devices, the cycle time T0 determined by the total number of the external devices is monitored.
To the scheduling device, and when the number m is less than the total number of the external devices, the cycle time T0
A disk access device comprising: a cycle time control means for outputting a shorter cycle time T1 to the scheduling device. 3. The disk access device according to claim 1, wherein the cycle time T1 has a relationship of T1 = (m / k) · T0, where k is the total number of the external devices. 4. A plurality of terminal devices which decompress and display compressed video data and output an access request signal for obtaining desired video data, and monitor whether or not the terminal devices are in a connected state. Then, a disk access device that operates the disk device according to an access request signal that is scheduled at each cycle time that is changed according to the number of connected terminal devices, and stores the video data controlled by the disk access device. Storage device and a buffer memory connected to each of the terminal devices, and data sending and buffer means for writing video data read from the storage device by the disk access device to these buffer memories. Video-on-demand device. 5. A plurality of terminal devices that decompress and display compressed video data and output an access request signal for obtaining desired video data, and the number of access request signals given from the terminal device. A disk access device that operates a disk device according to an access request signal that is scheduled according to a changed cycle time, a storage device that is controlled by the disk access device and that stores video data, and a connection to each of the terminal devices. On-demand device, which has a buffer memory configured to write the video data read from the storage device by the disk access device to the buffer memory and buffer means.