JPH0589000A - Real time information transfer control system - Google Patents

Abstract

PURPOSE:To prevent an area in a DMA window from being fixedly sea for a long time and to ease restriction to the number of lines to be stored in a center by using-specific command. CONSTITUTION:A transfer interface control part 43 in a host computer 36 issues a synchronizing command (o) to a transfer device 34. When an up transfer request does not exist in the device 34, the device 34 interrupts the command (o), disconnects connection with the computer 36 and releases a transfer interface 35. At the time of generating an up transfer request, the device 34 is connected to the computer 36 again and informs only the completion of the command (o). When the up transfer request exists at the time of issuing the command (o), the device 34 immediately informs the completion of the command (o). At the time of receiving the synchronizing command completion information, the computer 36 allocates an area in the DMA window and issues a receiving command (e) to the device 34.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multimedia communication terminal (hereinafter referred to as "terminal") connected via an ISDN communication network.
That. ) And a real-time multimedia communication information storage / exchange center (hereinafter referred to as “center”), in a real-time multimedia communication information storage / exchange service, between a transfer device and a host computer that constitute the center. The present invention relates to a real-time information transfer control method for controlling transfer of audio / video information and other real-time multimedia communication information (hereinafter referred to as "real-time information").

[0002] Here, the terminal has a function of simultaneously bidirectionally communicating real-time information in accordance with ISDN, and the center stores the real-time information sent from the terminal and the accumulated real-time information. It has a function to search for and send to the terminal. The functions in the center are realized by a transfer device, a host computer, and an interface (hereinafter, referred to as “communication interface”) that connects the transfer device and the host computer.

That is, the transfer device is connected to the ISDN communication network to terminate the communication line, buffers real-time information received from the terminal, assembles transfer information blocks, transfers the blocks to the host computer, and transfers them from the host computer. It has a function of decomposing a transfer information block to be transferred and transmitting it to the terminal. The host computer has a function of controlling a plurality of transfer devices according to the number of accommodated communication lines and accumulating, retrieving, and reproducing real-time information transmitted / received to / from the terminals.

[0004]

2. Description of the Related Art FIG. 3 is a block diagram showing a system configuration for realizing a real-time multimedia communication information storage / exchange service.

In the figure, a terminal 32 and a center 33 are connected via an ISDN communication network 31. The center 33 is I
The transfer device 34 is connected to the SDN communication network 31, and the host computer 36 is connected to the transfer device 34 via the communication interface 35.

In the real-time multimedia communication information storage and exchange service, a communication request from the terminal 32 to the center 33,
On the contrary, a communication request from the center 33 to the terminal 32 occurs concurrently. Therefore, also in the communication interface 35 in the center 33, a transfer request from the transfer device 34 to the host computer 36 (hereinafter referred to as “upstream transfer request”) and a transfer request from the host computer 36 to the transfer device 34 (hereinafter referred to as “transfer request”). "Downstream transfer request") occurs asynchronously, but a transfer control method that efficiently performs it is essential.

In the transfer control method in the transfer interface 35, it is necessary to consider the following three conditions at the same time. (1) In the input / output control method between the computer and the peripheral device, only the computer has the interface control right, and the peripheral device generally operates under the control of the computer.
Therefore, when using such a general-purpose computer as the host computer 36, it is necessary to adopt a method in which the host computer 36 also controls the transfer interface 35 as a control entity. (2) Since the real-time information communicated between the terminal 32 and the center 33 is composed of, for example, compression-encoded continuous voice, continuous still image or moving image, the transfer device 34 and the host computer 36 If a transfer delay occurs between the terminals, the terminal user recognizes that the audio or video is interrupted. Therefore, the upstream transfer request and the downstream transfer request in the transfer interface 35 need to be processed within a predetermined time. (3) From the viewpoint of the internal processing efficiency of the transfer device 34, it is convenient that the buffering of the real-time information in the transfer device 34 is performed in a logically meaningful unit such as a division corresponding to one screen of video information. Is good. Therefore, the size of the transfer block between the transfer device 34 and the host computer 36 is variable depending on the compression coding efficiency, and moreover it is generally long because it contains the video information. For this reason, the transfer interface 35 needs to apply a high-speed burst mode block transfer protocol.

Transfer interface 3 satisfying the above conditions
As a transfer control method in No. 5, in response to an upstream transfer request from the transfer device 34 that occurs asynchronously with the host computer 36, the host computer 36 issues a receive command to the transfer device 34 in advance to temporarily open the transfer interface 35. A method has been proposed in which, when an upstream transfer request occurs, the transfer device 34 reconnects to the host computer 36 and transfers the buffered real-time information as a response to the received command to the host computer 36 (for example, Information Processing Society of Japan Proceedings of the 41st National Convention, pp. 1-115, "How to apply SCSI to real-time video / audio transfer control device (lecture number 1Q-
2) ”).

In this transfer control method, the host computer 36 issues the command to the transfer device 34, so that
It conforms to the input / output control method of (1), and when the upstream transfer request occurs, the transfer device 34 can mainly start the transfer quickly, and the condition of the above (2) is satisfied. Further, by using the burst mode block transfer mechanism normally incorporated in the host computer 36 as the receive command function, high speed transfer of a large transfer block of real-time information is realized.
The condition of (3) above is satisfied.

Here, a detailed configuration example of the center 33 is shown in FIG.
An example of data transfer in the conventional transfer control method will be described with reference to FIG. In FIG. 4, the transfer device 34 has a real-time information buffer 40. The host computer 36 includes an arithmetic control unit 41, a main storage unit 42, a transfer interface control unit 43, and others, which are connected via an internal bus 44. The arithmetic control unit 41 includes the main storage unit 4 issued from itself and the transfer interface control unit 43.
2 has a memory management unit 45 for controlling access to the host computer 2 and performs internal processing of the host computer. The main storage unit 42 stores programs and data processed by the host computer. The transfer interface control unit 43 controls the transfer interface 35 and performs DMA transfer with the main storage unit 42 via the internal bus 44.

The memory management unit 45 has a window area for DMA transfer via the internal bus 44 (hereinafter referred to as "DMA window") in an address space managed by itself.
Owns. A DeHeis driver program (hereinafter, referred to as “DRV”) 46 that controls the transfer interface control unit 43 stored in the main storage unit 42 is a control program (hereinafter, “OS”) that manages the host computer system.
That. Each time a data transfer request requiring DMA is received via 47), an operation of allocating an area of a required size from the DMA window of the memory management unit 45 is performed. When the DMA data transfer is completed, the DRV 46 releases the area in the DMA window allocated for this data transfer so that it can be reused.

A program (hereinafter referred to as "AP") 48 of the host computer 36 that realizes the real-time multimedia communication information storage and switching service tells the transfer device 34 at any time point so that it can always respond to an upstream transfer request. And issues a transfer block reception request (FIG. 5a). The transfer block reception request 51 is an address (hereinafter, referred to as “AP reception buffer”) 49 of a memory area that receives the transfer block in the AP 48, and a maximum possible block length (hereinafter, referred to as “AP reception size”). Is issued by specifying. The DRV 46 firstly has D corresponding to the AP reception size.
An area in the MA window is allocated (FIG. 5b), the AP reception buffer 49 is set as the transfer destination, and secondly, the transfer interface control unit 43 receives the address and size of the area in the DMA window and the receive command to be issued to the transfer device 34. Necessary initialization is performed (FIG. 5c), and thirdly, the transfer interface control unit 43 is activated (FIG. 5d). The transfer interface control unit 43 sends the received command to the transfer device 34 via the transfer interface 35 according to the initial setting.
(FIG. 5e), the transfer interface 35 is once released (FIG. 5f).

When an upstream transfer request is generated, the transfer device 34 reconnects with the transfer interface control unit 43 (FIG. 5g), and the real time information buffered in the real time information buffer 40 as a response to the received command is sent to the host computer 3
Transfer to 3. The transfer interface control unit 43 sequentially delivers the data received from the transfer device 34 to the AP 48 via the area in the DMA window and stores it in the AP reception buffer 49 (FIG. 5h). When the transfer end is notified from the transfer device 34 (Fig. 5i), the transfer interface control unit 43 notifies the DRV 46 of the transfer end by an interrupt (Fig. 5j), and the DRV 46 releases the allocated area in the DMA window (Fig. 5k), and notifies the AP 48 of the completion of the transfer block reception request (FIG. 5l).

Regarding the downlink transfer request, AP48
A transfer block transmission request is issued to the transfer device 34 at the time when it is required by the above. However, the command issued to the transfer device 34 is a transmission command. , AP48
Is controlled in the same manner except that the data is sequentially received from and transmitted to the transfer device 34.

[0015]

As described above, in the data transfer between the transfer device 34 and the host computer 36 according to the conventional method, before the actual transfer interface 35 is driven, the data is transferred in the DMA window in the host computer 36. It is necessary to secure the area required for block transfer. In particular, regarding the upstream transfer request, the host computer 36 sets D so that the AP 48 can always respond to the transfer request from the transfer device 34.
Since an upstream transfer request from the transfer device 34 is waited in a state where a predetermined area is secured in the MA window, the area is almost fixedly secured in the DMA window. Therefore, when the number of lines accommodated in the center 33 increases and the number of the corresponding transfer devices 34 increases, the DMA
The area that is almost fixedly secured in the window for the upstream transfer request from each transfer device 34 also becomes large, which is a factor that restricts the number of accommodated lines.

Further, the size of the DMA window is generally a small area as compared with the entire address space of the host computer 36, while the transfer device 34 and the host computer 36 are used.
Since the size of the block transferred between and is real-time information such as voice and image, it is generally long. That is, since the area to be secured for each transfer device is large despite the limited area, the number of lines that can be accommodated in the center 33 is also severely limited.

The present invention prevents the area in the DMA window used for data transfer with each transfer device from being fixedly secured for a long time, and limits the number of lines accommodated in the center. It is an object to provide a real-time information transfer control method that can be relaxed.

[0018]

According to a first aspect of the present invention, a real time information received from a multimedia communication terminal via an ISDN communication network is assembled into a transfer information block and transferred to a host computer, and at the same time, a host computer is provided. A transfer device that decomposes a transfer information block transferred from a computer and sends it to a multimedia communication terminal, and a storage device that controls the transfer device and stores, retrieves, and reproduces real-time information transmitted to and received from the multimedia communication terminal. In the real-time information transfer control method in the transfer interface connecting with the host computer that performs the operation, the host computer can issue the transfer device to the transfer device at any time, and the transfer device can issue the transfer device to the host computer at the time of issue. If there is no data transfer request, the connection with the host computer is released and the transfer interface The opening, the at the time when the data transfer request is generated host computer and reconnect to complete execution,
When there is a data transfer request to the host computer in the transfer device at the time of issue, the execution is completed immediately, and upon the completion of the execution, a synchronous command is used to cause the host computer to detect the data transfer request of the transfer device. ..

According to a second aspect of the present invention, in the real-time information transfer control method according to the first aspect, the host computer detects a data transfer request in the transfer device upon completion of the synchronization command, and immediately after the detection, the host computer It is characterized in that the computer issues a reception command for instructing data reception to the transfer device.

[0020]

1 is a flow chart for explaining the basic procedure of the method of the present invention. In the present invention, a synchronization command is provided as a new command issued from the host computer 36 and processed by the transfer device 34. This synchronization command is a command that does not involve data transfer, and is issued to the transfer device 34 prior to the issuance of a receive command from the transfer interface control unit 43 to the transfer device 34 (FIG. 5e). However, no special processing is performed for this synchronous command in the transfer device 34, and if there is no upstream transfer request at that time, the transfer device 34 interrupts the synchronous command and disconnects from the host computer 36. The transfer interface 35 is opened. Further, the transfer device 34 reconnects to the host computer 36 at the time when the upstream transfer request is generated and notifies only the completion of the synchronization command. If there is an upstream transfer request in the transfer device 34 at the time of issuing the synchronization command, the completion of the synchronization command is immediately notified. The above is the invention according to claim 1.

In the host computer 36, the area in the DMA window is allocated by the completion notification of the synchronous command, and when the receive command is issued to the transfer device 34, the transfer device 34 is ready for the transfer data to the host computer 36. Therefore, once the host computer 36
It is possible to start data transfer immediately without disconnecting from and reconnecting later. The above is the invention according to claim 2.

As described above, in the method of the present invention, the host computer reserves the area in the DMA window after knowing in advance the occurrence of the upstream transfer request by the synchronous command, and then issues the receive command, whereby the DMA window It is possible to continuously perform the process from securing the area to starting and completing the data transfer. That is, in the past, the area was secured in the DMA window and the upstream transfer request from the transfer device was waited for. However, in the method of the present invention, there is almost no waiting time after the area is secured in the DMA window, and the area is It is possible to avoid a state that is fixedly secured for a long time.

[0023]

FIG. 2 is a diagram for explaining an example of data transfer by the real-time information transfer control system of the present invention.

In the figure, the AP 48 of the host computer 36
Issues a transfer block reception request by designating the address of the AP reception buffer 49 and the AP reception size as in the conventional method (FIG. 2a). Here, the DRV 46 performs initial setting for issuing a synchronization command to the transfer interface control unit 43 (FIG. 2m) and activates the transfer interface control unit 43 (FIG. 2n). The transfer interface control unit 43 issues a synchronization command to the transfer device 34 via the transfer interface 35 according to this initial setting (FIG. 2o), and waits for its completion.

When an upstream transfer request is generated, the transfer device 34 reconnects to the transfer interface controller 43 and notifies the completion of the synchronous command (FIG. 2p). The transfer interface control unit 43 notifies the DRV 46 of the completion of the synchronization command by an interrupt (FIG. 2q). DRV46
D is equivalent to the AP reception size due to this interrupt
An area in the MA window is allocated (FIG. 2b), the AP reception buffer 49 is set as a transfer destination, and subsequently, the transfer interface control unit 43 receives the address and size of the area in the DMA window and a reception command to be issued to the transfer device 34. The necessary initial settings are made (Fig. 2c), and the transfer interface control unit 43 is activated (Fig. 2d). The transfer interface control unit 43 issues the received command to the transfer device 34 via the transfer interface 35 in accordance with this initial setting (FIG. 2e).

In the transfer device 34, the upstream transfer request has already been notified to the host computer 36 by the completion notification of the synchronous command, and the real time information buffered in the real time information buffer 40 immediately according to the received command is sent to the host computer 36. Transfer to. Transfer interface control unit 43
Sequentially delivers the data received from the transfer device 34 to the AP 48 via the area in the DMA window and stores it in the AP reception buffer 49 (FIG. 2h). When the transfer end is notified from the transfer device 34 (FIG. 2i), the transfer interface control unit 43 notifies the DRV 46 of the transfer end by an interrupt (FIG. 2j). When the transfer end is notified by the interrupt, the DRV 46 releases the allocated area in the DMA window (FIG. 2k) and notifies the AP 48 of the completion of the transfer block reception request (FIG. 2l).

The downlink transfer request is the same as in the conventional system. Below, SCSI (Small Computer System In) is widely used as a standard input / output interface.
terface, ANSI X3.131-1986) is applied to the method of the present invention.

After issuing a synchronization command from the host computer 36 to the transfer device 34, the transfer interface 35 is temporarily released by using a SCSI message.
In-phase disconnect messages are applicable. With this function, the transfer device 34 uses SCSI.
The bus occupation state is released, and the host computer 36 can communicate with another transfer device. A SCSI reconnection function can be applied to the function of the transfer device 34 to reconnect to the host computer. This function is realized by a sequence in which when the transfer device 34 performs the arbitration phase and acquires the SCSI bus use right, the reselection phase and the message send-in in the message-in phase are followed. The transfer device 34 can notify the command completion to the host computer 36 in the status phase and the message in phase.

[0029]

As described above, according to the present invention, since the occupied time of the DMA area in the host computer is shortened to the net data transfer time, the data transfer request can surrender the DMA area in a short time. it can. Therefore, even if the number of transfer devices increases, the DMA area can be used with a short waiting time for each data transfer request, and a large number of lines can be accommodated.

Further, in the present invention, since one command is added to the conventional method, it is easy to realize, and since it can be controlled inside the DRV, the performance deterioration due to this method can be minimized.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a basic procedure of the method of the present invention.

FIG. 2 is a diagram illustrating an example of data transfer in the system of the present invention.

FIG. 3 is a block diagram showing a system configuration for realizing a real-time multimedia communication information storage / exchange service.

FIG. 4 is a block diagram showing a detailed configuration example of a center 33.

FIG. 5 is a diagram illustrating an example of data transfer in a conventional method.

[Explanation of symbols]

31 ISDN communication network 32 terminal (multimedia communication terminal) 33 center (real-time multimedia communication information storage and switching center) 34 transfer device 35 transfer interface 36 host computer 40 real-time information buffer 41 arithmetic control unit 42 main storage unit 43 transfer interface Control unit 44 Internal bus 45 Memory management unit 46 DRV (Device driver program that controls the transfer interface control unit 43) 47 OS (Control program that manages the host computer system) 48 AP (Real-time multimedia communication information storage and exchange service realized Host computer 36 program that executes) 49 AP receive buffer (address of memory area that receives transfer block in AP 48)

Claims (2)

[Claims] 1. A real-time information received from a multimedia communication terminal via an ISDN communication network is assembled into a transfer information block and transferred to a host computer, and at the same time, the transfer information block transferred from the host computer is decomposed to perform multi-processing. In a transfer interface that connects between a transfer device that transmits to a media communication terminal and a host computer that controls this transfer device and stores, retrieves, and reproduces real-time information transmitted and received to and from the multimedia communication terminal In the real-time information transfer control method, if the host computer can issue the transfer device to the transfer device at any time, and the transfer device does not have a data transfer request to the host computer at the time of the issue, When the data transfer request is generated by releasing the connection of the When the transfer device has a data transfer request for the host computer at the time of issuance, the execution is completed immediately, and upon completion of the execution, the data transfer of the transfer device to the host computer is completed. A real-time information transfer control method characterized by using a synchronous command to detect a request. 2. The real-time information transfer control method according to claim 1, wherein the host computer detects a data transfer request in the transfer device upon completion of the synchronization command, and immediately after the detection, the host computer sends the transfer device to the transfer device. A real-time information transfer control method characterized by issuing a reception command for instructing data reception.