JP3186453B2 - Data transmission device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a data transmitting apparatus which can transmit data in response to a plurality of random access requests by performing a short-time high-speed reading using a recording medium such as a tape. It is about.

[0002]

2. Description of the Related Art Conventionally, tape devices have been mainly used for recording and reproducing data such as large-capacity image data. However, the tape device is not suitable for applications requiring random access in order to perform sequential access.

A method for realizing random access using such a tape device is being studied. As one example, a data recording / reproducing apparatus is disclosed in JP-A-5-313829. The configuration of the data recording / reproducing apparatus disclosed in the above publication and its usage will be briefly described as a conventional example.

[0004] A conventional data recording / reproducing apparatus will be described below. FIG. 6 is a block diagram showing a configuration of a conventional data recording / reproducing apparatus. In FIG. 6, 1 is a computer having a CPU, 2 is a memory in the computer 1, 3 is a disk that is a storage device that can be randomly accessed, 5 is a tape drive storage device, 4 is a data drive storage device 5, and a disk 3 An input / output device that inputs and outputs data to and from the computer 1.

[0005] The data recording / reproducing apparatus configured as described above will be described. In order to continuously use data such as image data on the computer 1, the following operation is performed. Calculator 1 is provided with a memory for storing the current position of the head. When reading the image data, the data on the disk is read and reproduced at high speed while the head of the tape drive storage device 5 is moving, and after the head is moved, the data on the tape is reproduced. With this configuration, one computer 1 corresponds to one tape drive storage device 5, and the head is moved while the computer 1 moves.
It can be used continuously without data loss.

If this configuration is applied, an image data distribution system can be configured. The image data distribution system is a system from a data server device having a plurality of tape drive storage devices 5, a plurality of terminals, and a network. In the data server device, it is necessary to install the tape drive storage device 5 only capable of responding to the random access request. For example, in the case of a system that allows access from 20 terminals simultaneously, 20 tape drive storage devices 5 are required. Regarding the head access time, the data read from the tape drive storage device 5 at high speed in advance to the disk 3 is reproduced, and after the head moves, the data read from the tape drive storage device 5 is read. Is distributed to each terminal, so that data can be continuously transmitted to 20 terminals.

[0007]

However, the above-mentioned conventional configuration has a one-to-one configuration in which data is transmitted from one tape drive storage device to one computer or one terminal. Had become. When the number of terminals increases, the number of tape drive storage devices must be increased. Therefore, when the installation volume is limited, the number of transmittable deliveries is determined by the number of tape drive storage devices due to location restrictions.

[0008] The present invention solves the above-mentioned conventional problems, and in response to a plurality of read requests from one recording medium,
Reads data at high speed, accumulates data once, and continues to transmit only the accumulated data even when accessing the recording medium,
The amount of data read per unit time is
Read more than the amount of data
Calculate the travel time to the readout position and calculate the travel time
It is an object of the present invention to provide a data transmission device that can transmit data from one recording medium to a plurality of terminals by reading data in a minimum time .

[0009]

In order to achieve this object, a data transmitting apparatus according to the present invention comprises: a receiving unit for receiving a data distribution request from a plurality of terminals and generating a read request;
According to the read request, the read position is reached with respect to the recording medium.
Reading means for reading data by moving the
Access that is the travel time to the read position for the medium
Calculating means for calculating the order that minimizes the total time;
Temporary storage means for temporarily storing found data;
Received a data distribution request and temporarily stored data in the terminals.
Data amount of data to be sent out per unit time
Is the unit of data read from the recording medium.
Sending means that is smaller than the data amount per interval .

[0010]

According to the present invention, there is provided a recording medium having the above structure .
Movement for reading when reading multiple locations
Calculate the minimum travel time from the time and perform high-speed reading.
In addition, by accumulating data, it is possible to simultaneously transmit data from the transmission means to a plurality of terminals without stopping access time.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a data transmission device according to a first embodiment of the present invention. In FIG. 1, reference numeral 11 denotes a recording medium such as a tape, 12 denotes a receiving unit that receives a distribution request from a plurality of terminals and generates a reading request, 13 denotes a reading unit that receives a reading request and reads data from the recording medium 11, and 14 denotes a reading unit. A temporary storage means for storing the data read by the reading means 13, and a sending means 15 for sending the stored data to a terminal having a distribution request.

A description will be given of the data transmission apparatus of the present embodiment configured as described above. It is assumed that distribution requests for data such as video data are randomly issued from a plurality of terminals. Here, it is assumed that the data to be distributed is encoded data in which a video signal is encoded with high efficiency and the data is compressed. Data compression is performed by MPEG (Moving Picture).
res Expert Group)
A case where digital data subjected to data compression is used will be described. The MPEG system is internationally standardized, and a time signal for decoding and synchronization is defined along with video compression and audio compression. According to the MPEG1 standard, the data encoding speed is set to about 1.2 megabits per second (hereinafter Mb) for video.
ps), about 0.2Mbp for audio (for stereo)
When s is used and other control information is included, a data encoding rate of about 1.5 Mbps in total is adopted. Therefore, data compressed by the MPEG1 method is 1.5
If the data is transmitted at a transmission speed of about Mbps, the data can be decoded and reproduced on the receiving terminal side. When the distribution request from the terminal is delivered to the receiving means 12, a reading request is issued to the reading means 13. The read request includes information indicating the title desired to be distributed, address information of the requested terminal, distribution data information (identification information such as a still image or a moving image, distribution time, and running operation such as reproduction and pause). Content).

The read means 13 which has received the read request
Determines whether the title exists in the recording medium 11 and data is ready to be read. If the corresponding recording medium 11 is not mounted, the corresponding medium is mounted. The recording medium 11 may be provided as a matter of course, but it is preferable that the recording medium 11 be exchanged in consideration of regular title exchange and the like. If there is a corresponding title in the recording medium 11, the task starts reading the corresponding data from the recording medium 11. If a removable medium such as a tape is used as the recording medium 11, replacement is easy. Further, since the recording capacity is large, a large amount of data can be stored in a small space, and can be exchanged and used as needed.

Here, a case where a tape is used as the recording medium 11 will be described. Feed the tape at the fast forward position to the data recording position. Video and audio data recorded in the MPEG format and index information for referring to the recorded data position are recorded on the tape, and the tape is fast-forwarded with reference to the index information so that the target recording position can be specified. I have. Hereinafter, the tape feeding time to the target recording position will be described as an access time. After the elapse of the access time, data reading is started from the target position. This reading speed needs to be higher than a sending speed for sending data (for example, 1.5 Mbps in the case of the MPEG1 system). This means that if the reading speed is lower than the sending speed, the read data cannot be sent continuously. If the two speeds are equal, it means that data cannot be read during the access time, so that data cannot be sent during that time. Therefore, at least the reading speed needs to be higher than the sending speed. An example of the actual reading speed will be described later in detail.

The read data is stored in a temporary storage unit 14.
Is stored in Then, the data is continuously transmitted from the stored data to the target terminal. Temporary storage means 1
4, the data can be continuously transmitted even during the access time.
FIG. 2 shows the relationship between the access time, the data read time, and the data transmission time. FIG. 2 shows the processing contents at the time of performing distribution in response to a read request from three terminals over time. FIG. 2 shows the same recording medium 1 in particular.
This indicates that three types of accesses to 1 have occurred. In FIG. 2, reference numeral 21 indicates the relationship between the access time and the read time, and reference numeral 22 indicates each transmission time. The three types of accesses are referred to as access 1, access 2, and access 3, respectively. After the elapse of the access time for access 1, data is read at high speed. This time is referred to as lead 1. The read data is stored in the temporary storage means 14, and the transmission (transmission 1 in FIG. 2) is started at the same time as the next access 2 starts. Similarly, sending 2 and sending 3 are performed simultaneously. As shown in FIG. 2, during the time when the transmission 1 is being transmitted, the access time required for the next transmission 1, the data reading time, and the other (in FIG. 2, the transmission 2 and the transmission 3 in FIG. 2). ) It is necessary to perform processing related to transmission. In other words, in one data read, a necessary amount of data must be read in order to continue transmitting data during a time required for another transmission. Here, an example has been described in which transmission is started after data is read out and stored in the temporary storage unit 14. However, transmission may be started at the same time as storage in the temporary storage unit 14 is started.
In addition, since each access time changes depending on the recording position (for example, a tape or the like requires a maximum running time of the entire tape), it is calculated by a time that guarantees the maximum time of rewinding or fast-forwarding. It is necessary to read an amount of data that can be sent continuously even when the

In order to respond to a plurality of distribution requests, there is the following problem. When a new read request is issued,
The newly requested read must be added to the current read. Therefore, the reading unit 13 calculates the amount of read time required for the change in the newly added number of reads from the current amount of data read and the amount of data accumulated per read time, and changes the read time width. By transmitting the contents of this change from the reading means 13 to the temporary storage means 14 and the sending means 15, it is possible to cope with a change in the number of accesses.

In the case where the distribution request is a continuous video such as a movie, the reading means 13 repeatedly reads the subsequent data after the distribution request is issued from the terminal until a stop or pause request is issued. Required (corresponding to the second access 1 in FIG. 2). These repetitive controls are executed in the reading means 13. Therefore, in the read request,
By adding information such as continuous data and temporary data (such as a still image), it is possible to distinguish between those involving continuous operations and those that are performed only once (or a specific number of times).

It is assumed that a tape device has a data amount that can be recorded on a tape of 40 gigabytes (abbreviated as GB) or less and a time when the maximum fast-forward of the tape is performed is 90 seconds. The reading speed read from the reading means 13 is set to 20 Mb.
ps (approximately 19.3 Mbps to approximately 24 Mbps)
s) The amount of memory required for the temporary storage means 14 when the transmission speed to one terminal is 1.5 Mbps is calculated.
Based on the above assumption, if the access time is set to 90 seconds, one reading time is set to X seconds, and the number of terminals to be simultaneously transmitted is set to Y, it can be expressed as (Equation 1). Here, the description will be made on the assumption that the time required for writing and reading to and from the temporary storage means 14 is negligibly short compared to the access time and the read time by using a high-speed semiconductor memory such as a DRAM.

[0020]

(Equation 1)

An equation for calculating the amount of memory when the temporary storage means 14 is constituted by a semiconductor memory is shown in (Equation 2).

[0022]

(Equation 2)

Table 1 shows the results calculated from (Equation 1) and (Equation 2). The unit of the memory amount calculated by (Equation 2) is a bit, and in Table 1, the unit is converted into bytes and shown.

[0024]

[Table 1]

From the results shown in Table 1, it can be seen that if the memory amount is increased, the number of terminals that can transmit simultaneously can be increased. Actually, the amount of memory is determined in consideration of the cost of the mounted memory and the number that can be simultaneously transmitted. Here, the calculation is performed using the semiconductor memory, but a medium such as a magnetic disk may be used. However, in the case of a magnetic disk,
A seek time or the like is required to move the magnetic head. Therefore, it is necessary to consider the writing time and the reading time for the temporary storage means 14.

In the case where the DAT is adopted for the tape device, the read speed is, for example, about 4 Mbps (in the case where the DAT standard DDS-2 is adopted).
Mbps, which is considerably slower than the transmission speed (for example, MPE
(1.5 Mbps of G1 system)
It is possible to simultaneously transmit from two DATs to two terminals.

Although it has been described that the configuration of the temporary storage means 14 is configured by a semiconductor memory, the following realization example can be considered in practice. In one of them, data to be transmitted to a plurality of terminals is stored in a memory area of a separated address. As a result, the transmitting means 15 may read out the data stored at different addresses of the temporary storing means 14 and transmit the data to the respective terminals. When the last address of each memory area is reached, the data is stored again from the first address of the area. As a second means, memories having separate memory areas are configured, and each memory is
With the FO (first-in first-out) type, writing and reading of data to and from the semiconductor memory can be easily achieved asynchronously. As another means, the data is temporarily stored in the temporary storage means 14 as fixed packet data in which data added to the read data and destination information of the destination are added. Then, the stored data is sent to the sending means 15. The sending unit 15 stores the information in a destination memory or the like in the sending unit 15 while viewing the destination information. When data is written to the destination-specific destination memory, the written data can be transmitted at a fixed timing, which is the transmission timing (defined from the network side where the terminal and the data transmission device are connected).

If the transmitting means 15 has a function of outputting data at a constant rate (1.5 Mbps in this example) to a terminal requested to be distributed, a dedicated network for data distribution, a public telephone network, an ISDN network , For sending data to other dedicated lines. In order to read out data stored at a constant rate, as described above, the temporary storage means 14 is configured by a FIFO or the like, and data is read out according to output timing, or an internal memory is provided inside the transmission means 15. It reads out only necessary data from the internal memory and sends it out. With this configuration, the terminal only needs to receive distribution data such as a video transmitted at a constant rate and reproduce the video. Since the terminal does not need to have a buffer memory for received data, the cost of the terminal equipment can be reduced.

On the other hand, recording on the recording medium 11
By using compressed digital data such as MPEG1 for the data transmitted from 5, it is possible to store more movie titles than uncompressed data. Further, the compressed digital data includes time information in addition to video and audio. By referring to this time information and transmitting the data, the continuity of the data and the real-time timing required for reproduction can be known, so that data at a constant rate can be easily realized.

If there is a data amount of 40 GB, 1.5 Mb
20 or more movies compressed with MPEG1 of ps can be recorded. (If one movie is 180 minutes, a capacity of about 2 GB is required for one movie. A capacity of 40 GB is about 20.)
This is true). Therefore, it is possible to record 20 movie titles on the same recording medium 11 and distribute video data of a movie of the title recorded at the same time to a plurality of terminals. However, even when the embodiment of the present invention is used, at most 1
Only about 0 terminals can transmit data at the same time. In order to respond to requests from tens or hundreds of terminals, it is necessary to prepare a plurality of recording media 11 and have a configuration in which the reading means 13 can handle the plurality of recording media 11 simultaneously and separately.

In this embodiment, the case where a tape is used as the recording medium 11 has been described. This recording medium 11 is a CD-ROM.
It can also be realized by a disk such as a ROM device. This configuration can be applied to a disk in which the data read speed from the disk is twice as high as the transmission speed and the access time is slow. For a hard disk etc. with a short access time and a fast read speed, a configuration with a cache memory etc. inside the disk unit itself,
Since random access is easy, a single disk device can receive random distribution requests from a plurality of terminals without using the configuration of the present invention. In this embodiment,
It is effective if applied to the recording medium 11 that can store a large amount of data although the access time is long.

When the reading means 13 receives a read request when a plurality of recording media 11 exist, the fastest accessible (short access time) recording medium 1 is read.
By selecting 1 and reading the data, it is possible to respond to the request from the terminal as soon as possible, so that it is possible to configure a data transmission device that provides a data distribution service with a short waiting time for the user. .

Using the configuration of the first embodiment of the present invention,
Since it is possible to realize a data transmission device that reads out data at high speed from the transmission unit 15 in response to a plurality of read requests from one recording medium 11 and simultaneously transmits data to a plurality of terminals without ending access time, Recording medium 1
1 can be reduced in installation area of a tape device or the like for storing the information.

Next, a second embodiment will be described. FIG. 3 shows a block diagram of a configuration of a data transmission device for realizing the second embodiment. In FIG. 3, the components from the recording medium 11 to the sending means 15 are the same as those in the first embodiment shown in FIG. Reference numeral 16 in FIG. 3 denotes a calculating unit that calculates the order that minimizes the total access time according to the read request.

The addition of the calculating means 16 also makes the function of the reading means 13 different from that of the first embodiment. The process until the read request is issued from the receiving unit 12 is the same as that of the first embodiment. When a read request is issued, the calculation means 16
It requests the current reading state from the reading means 13 and acquires the reading execution state. When a plurality of readings are requested for the same recording medium 11, it is calculated where the newly requested reading should be added in the current reading order to enable efficient access. FIG. 4 shows an example of the effect of the calculating means 16. In FIG. 4, reference numeral 23 denotes the order of access to the tape as the recording medium 11 when the calculating means 16 is not used, and reference numeral 24 denotes the order of access when the calculating means 16 is provided.

Further, the calculating means 16 also calculates the amount of read time necessary for changing the newly added number of reads from the current number of reads and the amount of data accumulated according to the read time per read. Then, the read contents corresponding to the calculated change are transmitted to the reading means 13, and the reading order and the time width are changed. By transmitting the contents of this change from the reading means 13 to the temporary storage means 14 and the sending means 15, it is possible to cope with a change in the number of accesses.

The use of the configuration of the second embodiment can reduce the entire access time. If the access time can be reduced, the required data storage amount can be reduced even during the access time. Therefore, it is possible to reduce the data amount of the temporary storage unit 14 when performing the same number of accesses. Or, even if the data amount of the temporary storage unit 14 is the same,
More access times can be performed. By using the configuration of the second embodiment, it is possible to realize a data transmission device that simultaneously transmits data to more terminals than in the first embodiment without ending the access time.

Next, a third embodiment will be described. FIG. 5 shows a block diagram of a configuration of a data transmission device for realizing the third embodiment. In FIG. 5, the components from the recording medium 11 to the sending means 15 are the same as those in the first embodiment shown in FIG. Reference numeral 17 in FIG. 5 denotes overlap detection means for detecting overlap of read positions in accordance with a read request, and reference numeral 18 denotes data generation means for creating data of an overlap portion from the data stored in the temporary storage means 14.

Hereinafter, a third embodiment will be described. The process until the read request is issued from the receiving unit 12 is the same as that of the first embodiment. When a read request is issued, the overlap detection unit 17 requests the current read execution state from the read unit 13 and acquires the read execution state. The overlap detecting means 17 detects whether the newly requested read data area partially or completely matches the currently read data area. As a result of the detection, if there is an overlapping area, a request to read only the area excluding the reading of the overlapping part is issued to the reading unit 13. The temporary storage unit 14 stores data having no overlapping portion. The data generator 18 obtains the content of the occurrence of the overlapping portion from the overlap detector 17 and creates the data of the overlapping portion from the data stored in the temporary storage 14.

If the configuration is such that the overlapping portion is not read out,
The amount of data read can be reduced. Even if the read data amount is reduced, the data of the overlapping portion is generated by the data generating means 18, so that the data can be distributed to a plurality of terminals. If the read data amount is reduced, the total read time can be reduced.

As described above, when the configuration of the third embodiment is used, the entire reading time can be reduced. If the read time can be reduced, the access time can be increased by the reduction in the read time, and a greater number of accesses can be performed. By using the configuration of the third embodiment, it is possible to realize a data transmission device that simultaneously transmits data to more terminals than in the first embodiment without losing access time.

[0042]

As described above, according to the present invention, in response to a random access request from a plurality of terminals, data is read out from a recording medium at high speed, data is stored once, and the stored data is stored in the recording medium. at the time or during the reading of data transmission for the data to the other terminal access also continues to send, at the time the unit
The amount of read data per interval is based on the total
By reading more than the output data amount,
When reading from multiple locations,
High-speed reading by calculating the minimum travel time from the travel time
And storing the data, it is possible to simultaneously transmit data from the transmission means to a plurality of terminals without ending the access time.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a data transmission device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of the operation of the data transmission device according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a data transmission device according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an access order of a data transmission device according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a data transmission device according to a third embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a data recording / reproducing device in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Recording medium 12 Receiving means 13 Reading means 14 Temporary storage means 15 Sending means 16 Calculation means 17 Overlap detection means 18 Data generation means

Continued on the front page (72) Inventor Koji Takeda 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. ) References JP-A-5-35407 (JP, A) JP-A-6-4594 (JP, A) JP-A-7-175817 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB G06F 3/06 303 G06F 13/10 340

Claims (5)

(57) [Claims] 1. A method for receiving data distribution requests from a plurality of terminals.
Receiving means for generating a read request; and a read position for a recording medium in accordance with the read request.
Reading means for moving and reading data, and a moving time to a reading position with respect to the recording medium.
A calculator that calculates the order that minimizes the total access time
And a temporary storage unit for temporarily storing the read data; and temporarily storing the read data in the plurality of terminals upon receiving the data distribution request.
Data per unit time for sending
Of the data read from the recording medium.
A data transmission device comprising: a transmission unit having a data amount smaller than a data amount per unit time . 2. Receiving a data distribution request from a plurality of terminals
Receiving means for generating a read request, wherein the receiving means transmits a plurality of distribution requests having different read positions;
When the data is received, the read data is
Overlap to detect overlap when part or all overlap
The detecting means and the read request for reading the overlapping portion first;
Only valid and the recording medium according to the read request.
Read to read data by moving to read position
Output means, temporary storage means for storing the read data, and data of the overlapping portion stored in the temporary storage means.
Means for generating data from the data , and receiving the data distribution request and temporarily storing the data in the plurality of terminals.
Data per unit time for sending
Of the data read from the recording medium.
A data transmission device comprising: a transmission unit having a data amount smaller than a data amount per unit time . Wherein delivery means, distributed to a plurality of terminals with a request, each data transmission apparatus according to claim 1 or claim 2, wherein the continuing sending continuous data at a constant rate. 4. 請 using removable tape recording medium
3. The data transmission device according to claim 1 or claim 2 . 5. The data transmitting apparatus according to claim 1 , wherein the data recorded on the recording medium and transmitted from the transmitting means is compressed digital data.