JP3040743B2 - Video library system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video for simultaneously reading a plurality of pieces of video information from an information storage device such as a disk device on which a large number of video information including audio information are recorded after being compressed and encoded. The present invention relates to a library system, and is used for a video-on-demand system or the like that simultaneously provides a plurality of pieces of video information via a network in response to requests from a plurality of terminal devices.

[0002]

2. Description of the Related Art A video library system as disclosed in Japanese Patent Application Laid-Open No. Hei 4-269087 is known as a conventional multiplex reading apparatus for video information of this kind. FIG. 6 is a configuration diagram of a conventional video library system. A disk device DK101, which is an information storage device for compressing and storing video information, stores a plurality of buffer memories BM101, BM102,
.., BM132, which are all controlled by the control device CN101.

FIG. 7 shows a timing chart of control in a conventional multiplex reading system. In the control device CN101, for example, 32 periodic time slots TS
, TS132, one control time slot sequence CTS101 is generated, and in each period, the first terminal system TE1 is used in the time slot TS101.
01 to the buffer memory BM101 of time slot T
In S102, the buffer memory B of the second terminal system TE102
In each time slot, different video information is read from the disk device DK101 as an information storage device, and the transfer destination of the information is set to a predetermined buffer memory BM10 by the switch SW101.
1, BM102, ... and write it,
The video information from the buffer memories BM101, BM102,...
.. Are decoded into video signals, and the video signals are displayed on subsequent monitors TV101, TV102,... To realize multiplexed video display on a plurality of terminals.

In a conventional video library system, in response to a request for reading video information from a terminal, one not-yet-occupied one within one cycle of a control time slot sequence is used.
One empty slot is searched for, and thereafter, reading from the information storage device is periodically performed using the searched time slot. Therefore, after the video read request arrives, the reading of the video information is waited until an empty slot in the control time slot sequence comes around. The response time from the issuance of this request to the end of the reading of the video information from the information storage device for the first time slot for the request is as follows. The worst case occurs when the slot is issued immediately after an empty slot, and the waiting time is equal to the length of one cycle.

For example, in FIG. 7, it is assumed that the n-th terminal issues a video information read request REQ101 at the end of the time slot TS132 in the first cycle. First, an empty time slot is searched from time slots for one cycle from that time. At this time, if the time slots TS101 to TS131 are already occupied and only the time slot TS132 is vacant, the request RE
Q101 is assigned to time slot TS132,
Reading of video information from the information storage device waits until the time slot TS132 of the second cycle. At this time, the start point RES101 of the monitor projection on the n-th terminal
Is exactly one cycle delayed from the time of the request REQ101. For example, if the number of time slots is 32 and one time slot is 125 ms, 4
Equivalent to a second delay.

In the conventional multiplex reading method, in order to shorten the worst response time, it is necessary to shorten each time slot and shorten one cycle. On the other hand, at the boundary of a time slot in the time division multiplex read control method, switching of read information in an information storage device generally requires an overhead time. For example, when a magnetic disk is used as the information storage device, it is necessary to switch the block to be read on the disk, and a head seek for that and an overhead time for sector search are required. Therefore, shortening each time slot relatively shortens the ratio of the actual data read time from the information storage device in each time slot, and lowers the effective average data transfer speed in the information storage device. Cause.

For example, if the overhead time is fixed at 50
If the time slot is 125 ms, the read efficiency of the disk device is 60% (= 75/12).
However, if the time slot is reduced to half, that is, 62.5 ms, the readout efficiency of the information storage device becomes 20% (=
12.5 / 62.5), and the average data read speed is reduced to 1/3.

[0008]

As described above, if each time slot is shortened to shorten the worst response time, the average data reading speed in the information storage device is reduced, and as a result, the multiplicity is reduced. There was a problem. In order to solve this problem, the present inventors have proposed a video library system which can always secure an empty time slot within the maximum phase difference of the control time slot sequence after receiving a request for reading video information. However, in this case, the first few segments of the video information provided from the center may be missing.

In the prior art, since each terminal has no video information content, in order to identify video information having similar attribute information such as a title, the center is actually accessed by accessing the video information. It was necessary to read and confirm the contents.

According to the present invention, in a video library system capable of shortening the worst response time for each video information read request without lowering the multiplicity, the first few segments of the video information provided from the center are missing. The purpose is to be able to display complete video information even when there is a problem. It is another object of the present invention to enable each terminal to check video information without accessing a center.

[0011]

In order to solve the above-mentioned problems, a video library system according to the present invention is, for example, shown in FIG.
It has each means as shown in FIG. In FIG. 1, 1 is a center, 2 is video information, 3 is an information storage device, 4 is a switch unit, 5 is a control device, 11, 11 'are terminals, 21, 21'.
Is a buffer memory, 31, 31 'are data storage units, 4
1, 41 'represents a data synthesizing unit, and 51, 51' represent a data selecting unit.

A system to which the present invention is applied is, for example, an information storage device 3 for reading out video information 2 which has conventionally been one set.
Are prepared, the video information 2 is divided into units that can be read in one time slot, and the divided information is distributed and stored in each information storage device 3. Also, a plurality of switches SW1, SW2, which form a pair with the information storage device 3 and switch the transfer destination of video information to a buffer memory of a predetermined terminal for each time slot.
.. Are provided. Then, in order to control the readout of the distributed and stored video information, a time slot sequence having the same period and having a different phase is generated for each set of the information storage device 3 and the switch of the switch unit 4, and new video information is generated. In response to the read request of No. 2, an unused time slot is selected from all the time slot columns, and the information storage device 3 corresponding to the selected time slot column in each of the time slot columns selects the unused time slot. The video information 2 corresponding to the read request is read, and the transfer destination of the read video information 2 is changed by the corresponding switch unit 4 to the buffer memories 21, 21 of the terminals 11, 11 ',. ′,
And a control device 5 for performing control for switching to.

According to the present invention, for example, in the case of the above-mentioned system, the provided video information 2 does not start from the first segment, and a maximum of (the number of information storage devices-1) information segments may be lost. Terminal 1 to deal with
On the 1, 11 'side, a part of the head of video information 2 is
Data storage units 31 and 31 ′ that accumulate and accumulate in the center 1
A data synthesizing unit 41 for synthesizing the video information 2 from the center 1 and the video information stored in the terminals 11 and 11 ';
41 'and data selectors 51 and 51' for switching between synthesized video information and stored video information.

First, the operation of an example of a system to which the present invention is applied will be described. The periodic time slot control for each combination of the information storage device and the switch is basically the same as the control in the conventional multiplex readout device for each of the combinations. The combination of a plurality of information storage devices and switches is executed in parallel, and the video information from each of the combinations is synthesized in each buffer memory, thereby realizing time-division multiplex reading of the plurality of video information.

At this time, each piece of video information is divided into segments to be read out in one time slot, and sequentially distributed and stored in each information storage device, so that the video information cannot be read out because it is stored in another information storage device. If the missing of a few segments at the head of the information is allowed, the reading of the predetermined video information can be started from a combination of an arbitrary information storage device and a switch.

Therefore, in response to a read request for video information from the outside, conventionally, an empty slot is searched from one control time slot sequence, and time is waited until the searched empty time slot is reached. , The video information is read out using the time slot. In the present invention, an empty time slot is searched in parallel from all the control time slot columns having a phase difference, and the searched empty time slot is searched. To read the requested video information.

In this method of searching for an empty time slot, an empty time slot can be found within a maximum value of the phase difference of each control time slot sequence from an arbitrary point in time. Therefore, the worst response time is limited to within the maximum value of the phase difference of each control time slot train cycle, and the worst response time is reduced.

According to the present invention, the data storage section of the terminal overlaps with the center at least the information segment of the video information of each video information stored in the center which may be lost when the center provides the video information. If the video information actually provided by the center is missing in the first few segments in the data synthesizing unit in the terminal, the segments of the video information stored in the data accumulating unit are supplemented by supplementing the segments. , Synthesizes complete video information without any missing heads.

When the user views all of the video information in the data selection section of the terminal, the display screen is switched to the video information from the data synthesis section, and a screen of complete video information without a head loss is displayed. . On the other hand, when the user only checks the content of the video information, the display screen is switched to the video information from the data storage unit, and images of several segments of the video information stored in the data storage unit are displayed.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing an embodiment of the present invention, an example of a system to which the present invention is applied will be described. Of course, the present invention is applicable not only to the system described below.

FIG. 2 is a diagram showing a configuration example of a system to which the present invention is applied. Disk devices DK1, DK2, DK3, and DK4, such as magnetic disks, are connected to switches SW1, SW2, SW3, and SW4, respectively, as an information storage device for compression-encoded video information. Each of the switches SW1,..., SW4 is connected to 32 buffer memories BM1, BM2,. Each disk device, each switch, and each buffer memory are controlled by the control device CN1.

Disk devices DK1, DK for each video information
FIG. 3 shows the state of accumulation in DK3, DK3, and DK4. One piece of compression-encoded video information V1 is output for each segment that can be read in one time slot from the beginning.
, SG2, SG3, SG4, SG5, SG6,..., And SG (SG1, SG5,.
k + 1), ... SG2, SG6, ..., SG (4
k + 2), ... SG3, SG7, ..., SG (4
k + 3),... SG4, SG8,.
(k + 4),... (k = 0, 1, 2, 3, 4,.

FIG. 4 is an operation timing chart of the system shown in FIG. The control device CN1 is a combination of each disk device and switch DK1-SW1, DK2-SW
2, DK3-SW3 and DK4-SW4, respectively, control time slot sequences CTS1, CTS2, and CTS1, each having a period of 32 time slots of TS1 to TS32.
Generate TS3 and CTS4. In this example, each control time slot sequence CTS1, CTS2, CTS3, CTS4
Are assumed to be out of phase with each other by eight time slots.

The control unit CN1 controls the time slots TS1 to TS32 in each control time slot sequence.
Each combination of the disk device and the switch is instructed to read a predetermined segment and transfer the video information to a predetermined buffer memory. In each control time slot sequence, the same video information segment is read out in the same numbered time slot, and its transfer destination is switched to the same buffer memory.

For example, in the time slot TS1 of the control time slot sequence CTS1, the first segment SG1 of certain video information is read using DK1-SW1, and its transfer destination is set to a certain buffer memory BMk (k is 1 to 32).
, The second segment SG2 of the same video information is read using the DK2-SW2 in the same time slot TS1 of the control time slot sequence CTS2, and the transfer destination is switched to the same buffer memory BMk. In the same time slot TS1 of the column CTS3, the third segment SG3 of the same video information is read out using the DK3-SW3, and its transfer destination is switched to the same buffer memory BMk. , DK4-
Using SW4, the fourth segment SG4 of the same video information is read, and its transfer destination is set to the same buffer memory B.
Switch to Mk.

In this way, each segment of one piece of video information is read out through each combination of the disk device and the switch in order, and written into one buffer memory BMk. In the buffer memory BMk, the sequentially written segments are sequentially sent to the subsequent decoder DEk. The decoder DEk decodes video information into a video signal for each segment, and decodes the video signal into a subsequent monitor TVk.
Projected on.

The video signal included in one segment corresponds to the time of the phase difference of each control time slot sequence, and the read / buffer memory of the next segment must be read before the video display of one segment is completed. The writing / decoding is completed, and the next video signal is input. In this embodiment, since the cycle of each control time slot sequence is 32 time slots, individual video display can be performed on monitors of up to 32 terminals.

In FIG. 4, when there is a video information read request REQ1 from the nth terminal, 4
Control time slot sequence CTS1, CTS2, CTS
3, search for an empty time slot for CTS4, and start reading the requested video information using the searched empty time slot. At this time, since each control time slot sequence has a phase difference of each eight time slots, no matter which of 32 available time slots TS1 to TS32, eight time slots are required after the arrival of the request REQ1. An empty time slot can be searched within.

For example, T out of 32 time slots
Suppose that S21 was the only empty time slot,
The video information request REQ1 is an empty time slot TS
Even if it arrives at the end of step 21, reading of the first segment can be started in TS21 of the first cycle in CTS1. As described above, the worst time of the response time coincides with the eight time slots, which is the phase difference between the control time slot trains.

However, at this time, the vacant time slot is the control time slot sequence C corresponding to DK2-SW2.
When the video information is selected from TS2, the video information starts to be read from SG2 which is the head of the segment stored in the disk device DK2.
Will be missing from the read video information. Similarly, if an empty time slot is selected from CTS3 or CTS4, SG1 and SG2 of the segment or SG1, SG2 and SG3 of the segment will be missing respectively.

As described above, depending on the control time slot sequence to which the selected vacant time slot belongs, a maximum of "(the number of pairs of disk devices and switches) -1" is omitted.

According to the present invention, for example, in the above-described system, it is possible to prevent the head segment from being lost. FIG. 5 is an apparatus configuration diagram according to the embodiment of the present invention.

The terminal TE50 has a data storage section M1, a data synthesis section C1, and a data selection section TSW1. Assuming that the number of disk devices in the center 1 is 3, the maximum head loss of the video information V1 provided from the center 1 is 2 segments. Therefore, two copies of SG1 and SG2 of the video information stored in the center 1 are stored in the data storage unit M1.

When the user wants to view all of the video information, the data selector TSW1 is switched to the data synthesizer C1, and the missing portion of the video information V1 provided from the center 1 is stored in the segment stored in the data storage M1. SG1,
A screen of complete video information without head loss is displayed, supplemented by SG2.

On the other hand, when the user only confirms the content of the video information, the data selection unit TSW1 is switched to the data storage unit M1, and two segments of SG1 and SG2 of each video information held in the data storage unit M1. Is displayed repeatedly. For example, a video menu is formed by reducing the information of each two segments and displaying a list of the first two segments of a plurality of pieces of video information in a list. 1 can also be used to select the video information requested.

[0036]

As described above, according to the present invention, after receiving a read request for video information, an empty time slot is always ensured within the maximum phase difference of the control time slot sequence. In a system that shortens the worst response time, the top information of each piece of video information stored in the center is duplicated in the data storage section of the terminal. It is possible to supplement the information and display complete video information. Also, when confirming the content of the video information at the terminal, it is possible to display a part of the content without accessing the center.

[Brief description of the drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a diagram illustrating a configuration example of a system to which the present invention is applied.

FIG. 3 is a diagram showing a method for storing video information in each disk device in the system shown in FIG. 2;

FIG. 4 is an operation timing chart of the system shown in FIG. 2;

FIG. 5 is a device configuration diagram according to the embodiment of the present invention.

FIG. 6 is an apparatus configuration diagram of an example of a conventional video information multiplex reading apparatus.

7 is a timing chart at the time of operation of the conventional device shown in FIG. 6;

[Explanation of symbols]

Reference Signs List 1 center 2 video information 3 information storage device 4 switch unit 5 control device 11, 11 'terminal 21, 21' buffer memory 31, 31 'data storage unit 41, 41' data synthesis unit 51, 51 'data selection unit DK1-DK4 Disk device (information storage device) SW1 to SW4 Switch BM1 to BM32 Buffer memory DE1 to DE32 Video information decoder TV1 to TV32 Video signal display monitor TE1 to TE32 First to 32nd terminal system device group CN1 Control device V1 One piece of compression-encoded video information SG1 to SG8, ... Segments TS1 to TS32 Time slots CTS1 to CTS4 Control time slot sequence REQ1 Request point of video information RES1 Start point of display on monitor TIME1, ... Response time

Continuation of the front page (72) Inventor Kazutoshi Nishimura 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Osamu Nakano 1-16-1 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone (72) Inventor Tatsuo Mori 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) References JP-A-4-269087 (JP, A) (58) Fields investigated Int.Cl. ⁷ , DB name) H04N 5/91-5/956 G06F 17/30 H04N 7/173 H04N 5/78

Claims (1)

(57) [Claims] 1. A video library system for reading video information stored in a center in advance and providing the read information to a plurality of terminals, wherein the center stores the video information in response to a video information read request from the terminal. From the center of the video information, and the terminal sends the video information to the requesting terminal. A data storage unit for overlapping storage, a data synthesis unit for synthesizing video information from the center with video information stored in the data storage unit, and a display screen for displaying video information from the data storage unit And a data selection unit that switches between video information from the data synthesis unit.