JPH0981472A - Scheduler of media server - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize the scheduling to which priority is added by preferentially performing reproduction process, retransmission process, etc., being the highest in priority. SOLUTION: A scheduler 10 is provided with a body processing part 1, a time monitoring part 2, a data transfer part 3 and a priority calculation part 4. By the transfer processing of one time, the number of transfer bytes for which a transfer processing should be performed is determined. In accordance with this determination, data is transferred, the number of transferred bytes is considered and the calculation of the priority for the data waiting for transfer which is held in the scheduler is carried out. Next, a priority bit 20 is generated. Further, the priority bit corresponding to each processing command is compared. The larger priority bit, that is, the bit with higher priority is determined to be transferred first and the bit with lower priority is set to be transferred later. Namely, reproduction process and retransmission process being high in priority are made to be preferentially performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scheduler of a media server for storing media such as moving images, still images, and sounds as a database and transmitting data to a plurality of players via a network while satisfying real-time performance. .

[0002]

2. Description of the Related Art For example, in a video-on-demand system, image data such as moving images and still images are stored in a large-capacity storage medium, and arbitrary images are supplied to a plurality of players connected via a network. The player is
For example, it is configured by a device called a dedicated set top box such as a cable television receiver. In each player, a user sends a processing command such as reproduction of an arbitrary image, fast forward, and rewind to a media server provided with a storage medium. The media server accepts this processing command and transfers data to each player. When supplying such a moving image or sound, the player cannot smoothly play back unless a constant transfer rate is maintained. Therefore, the media server needs a precise scheduling function for data transfer.

[0003]

By the way, the conventional media server scheduler as described above has the following problems to be solved. When scheduling this type of data transfer processing, for example, a first-in first-out method is conceivable in which data transfer is performed first for the player who received the processing command first. However, for example, when reproducing a moving image, there are processing commands having various contents such as normal reproduction, fast-forward reproduction, reverse reproduction, and stop of reproduction. Further, the configuration of each player is not uniform, and for example, some players have a large-capacity buffer memory, and some players have a small buffer memory capacity. Also, not only video-on-demand system,
In complex systems where various media such as still images, voice, text, etc. are transferred via a network and various devices such as workstations and personal computers receive and reproduce data, prompt and A simple and rational scheduling process is required.

[0004]

The present invention adopts the following constitution in order to solve the above points. <Structure> The media server scheduler of the present invention receives a processing command including data transfer requests from a plurality of players, reads the data from a storage medium, and executes data transfer and processing command requiring real-time processing. For scheduling,
In addition to the main body processing unit that receives processing commands from each player and the processing commands, the priority corresponding to the type is set, and the smaller the buffer memory provided in the requesting player, the higher the priority, The system includes a priority setting unit that determines the priority obtained by correcting the priority of the processing command, and a data transfer unit that, when a plurality of processing command receptions compete, performs data transfer in order from the data transfer request with the higher priority.

<Explanation> From each player, various processing commands for requesting data transfer, transfer stop request, etc. are sent to the media server. Not all the processing commands require real-time processing. Scheduling makes a plan that considers the data transfer rate, etc., so as to satisfy the required real-time property when executing processing commands from all players.
That is, a data resend request after a data transfer failure has a higher priority than an ordinary data transfer request, and therefore has a higher priority. In addition, if the buffer memory of the player is small, the transfer rate must be increased, thus increasing the priority. In this way, the type of processing command and the capacity of the buffer memory are factors that determine the priority, so the final priority is determined by considering both. When correcting the priority of the processing command with the priority set from the capacity of the buffer memory Consider both the type and capacity of the processing command, for example, either one may be prioritized, or each of them may be weighted appropriately. Is also good. As a result, it is possible to optimize the data transfer processing by dynamically determining the priority for executing these in accordance with the received processing commands for each data transfer.

<Structure> The priority setting means generates a priority bit indicating the priority for each data transfer for one time corresponding to each received processing command, and controls the data transfer in accordance with the display of the priority bit. To do. As for the priority bit, it is preferable to allocate a processing command to each bit on the upper side in descending order of priority, and a complementary number to the buffer memory capacity of the requesting player on the lower bit.

<Explanation> Since high-speed processing is required for the priority calculation processing, simple and reliable processing is preferable.
If the priority bit is configured as described above, priority can be displayed by setting 1 to the bit corresponding to the processing command and connecting the complement of the buffer memory capacity to the lower side. The player connected to the network and the buffer memory capacity thereof are known in advance to the media server side, and the calculation of the complement and the like can be executed in advance, and the calculation processing is extremely simple and fast. The reason why the processing command is set to the high-order bit is that the capacity of the buffer memory may be negligible depending on the content of the processing command. The complement is taken because the smaller the capacity of the buffer memory, the higher the priority needs to be.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to specific examples. <Specific Example> FIG. 1 is a block diagram showing the configuration of the scheduler of the media server of the present invention. The scheduler 10 includes a main body processing unit 1 and a time monitoring unit 2.
A data transfer unit 3 and a priority calculation unit 4. The main body control unit 1 is a unit that receives a processing command from the player 5. The time monitoring unit 2 is configured by a clock circuit or the like that determines a cycle of transfer data in order to transfer the data at a constant transfer rate and supplies time data for the transfer operation to the main body processing unit 1. . The data transfer unit 3 is a unit that transfers data to the player 5 according to the priority determined by the priority calculation unit 4. The transfer data is temporarily stored in a buffer memory or the like (not shown) and is sequentially read and transferred to the player 5. The priority calculation unit 4 uses the priority bit 20 which will be described in detail later.
Is generated, and the execution order of each processing command is calculated according to the display of this priority bit.

FIG. 2 shows a block diagram of the entire system. The scheduler 10 as described above operates by being incorporated in the following system. In this system, a media server 7 is connected to a plurality of players 5 via a network 6. Then, when each player 5 sends an arbitrary processing command to the media server 7 at an arbitrary timing, the media server 7 accepts the command and operates to read and transfer the corresponding data from the storage medium 11. For this purpose, the media server 7 is provided with a main process 8, a storage medium access process 9, and a scheduler 10. The main process 8 is a part that receives a command sent from the player 5 and executes a command receiving process with the player 5. When the main process 8 receives a command, the storage medium access process 9
A request for reading the corresponding data is issued to. Further, the main process 8 sends the received processing command to the scheduler 10, and this processing command is used for priority calculation by the priority calculation unit 4 through the main body control unit 1 shown in FIG. The storage medium access process 9 is a part that performs a process of reading the corresponding data from the storage medium 11 according to a request from the main process 8 and transferring the data to the scheduler 10. On the other hand, the scheduler 10 temporarily stores the data thus read and transferred in the buffer memory as described above, and temporarily stores the data based on the processing commands from the plurality of players 5 in the buffer memory. When
This is a part that schedules the transfer order according to priority bits and performs the scheduling so as to guarantee the real-time property of data transfer.

FIG. 3 shows a conceptual diagram of the data transfer operation. In order to guarantee the real-time property of data transfer, data transfer is performed to each player 5, for example, as shown in this figure. First, in FIG. 3A, player A, player B, and player C exist, and each player has the same configuration and the same buffer memory.
Moreover, it is assumed that the processing requests are accepted in the order of the players A, B, and C. In this case, scheduling is performed in the direction of the arrow shown in the figure, and data transfer is performed in the processing command reception order.

Even if the processing commands are accepted in this order, the capacity of the buffer memory of each player may differ, for example. In the example of (b) in this figure, the buffer memory capacity of player A is three times the buffer memory capacity of player C, and
2 shows the scheduling in the case where the buffer memory capacity of is twice as large as the buffer memory capacity of the player C.
In this case, the transfer rate is set to 1 for player A, 2 for player B, and 3 for player C. Therefore, first transfer one unit of data to player A,
Next, 1 unit of data is transferred to player C, and further 1 unit of data is transferred to player B. Thereafter, one cycle of player C, player B, player C according to the capacity of the buffer memory, That is, the number of times data is transferred to each player is increased or decreased in a time cycle that makes one round of this circle.

Thus, the size of the buffer memory is
It is an important factor in determining the priority of data transfer, that is, the priority. On the other hand, the processing command includes data playback,
There are various contents such as reverse play, fast forward play, fast forward reverse play, pause, and stop. These are processing commands that are often used to transfer video data, but the playback request does not maintain a constant transfer rate because the image is disturbed, so
It must have a high priority. However, in the case of a processing command requesting a pause or stop, lowering the priority does not cause a big problem. As for the relationship with the buffer memory capacity described above, it is not necessary to consider the buffer memory capacity of the requesting player with respect to the processing command requesting the stop. Therefore, it can be said that it is preferable to first set the priority mainly on the content of the processing command, and to correct the priority in consideration of the capacity of the buffer memory.

The priority bit 20 shown in FIG.
Is generated from such an idea. That is, here, the upper 5 bits of the priority bit 20 composed of 16 bits are associated with each command. The most significant bit is assigned to the processing command of the reproduction request having the highest priority. When this bit is “1”, it is a reproduction request processing command. In other cases, it is “0”. Therefore, when only the upper bits of the priority bit 20 are targeted for comparison, the priority bit corresponding to the processing command of the reproduction request may have higher priority than the priority bits of the processing commands corresponding to other requests. It can be easily identified by comparison.

The lower 10 bits are a bit for displaying the buffer size, that is, the capacity of the buffer memory. It should be noted that the smaller the capacity of the buffer memory, the higher the priority must be. Therefore, if a notification corresponding to the size of the buffer memory is directly assigned to this priority bit, the opposite result will be obtained. Therefore, the size of the buffer memory is complemented and assigned here. As a concrete method of the arithmetic processing, the capacity of the buffer memory is represented by the number of bytes or the like, and this is complemented and assigned to the lower bits. Further, in this example, the retransmission flag is assigned to the least significant bit. The retransmission flag is set to "1" when the data is once transferred according to the reproduction request or the like and the data transfer fails and the same data transfer request is made. If such a re-sending process is not executed prior to other requests, image distortion will occur on the player side.
Therefore, the command having this retransmission flag is given the highest priority. That is, when there is the same command, the command with the retransmission flag of "1" is processed with higher priority.

It should be noted that such priority bit 2
For generation of 0, for example, a constant bit conversion table corresponding to a command is generated in advance, and the upper bits are automatically generated. Further, a table in which the complement of the buffer size of the player corresponding to the request source address or the like is calculated in advance is provided, and the conversion processing is performed, so that the lower-order bits are generated very quickly. Therefore, the priority bit 20 as described above enables rapid priority display that matches the high speed of scheduling.

It is also possible to generate the data indicating the priority having the same function as the priority bit 20 by another method. For example, set a constant weighted constant for each processing command,
It is also possible to set a constant weighted with respect to the buffer size in relation to the processing command, add these or obtain a product, perform a certain arithmetic processing, and generate a priority bit.

Finally, the specific operation of the scheduler 10 will be described in order using a flow chart. FIG. 4 is an operation flowchart of the scheduler. First, in step S1, the scheduler waits until the transfer time comes according to the time displayed by the time monitoring unit 2 shown in FIG. This transfer time is set in consideration of the processing time for transferring one unit of data and the time such as scheduling that should be executed immediately before that.

Next, in step S2, the number of transfer bytes to be transferred in one transfer process is determined. The number of transfer bytes cannot be set indefinitely in relation to the transfer cycle, but some increase or decrease is allowed. The number of transfer bytes is set to at least the minimum transfer size of the buffer memory provided as an interface between the scheduler and the network. That is, the number of bytes is set to a unit amount such as 4096 bytes. In the next step S3, the data is transferred according to this determination, and in step S4, the priority of the data waiting for transfer held by the scheduler is calculated in consideration of the number of transferred bytes.

That is, in step S5, it is first determined whether or not processing commands have been accepted in competition at the same time. If there is a time difference in receiving the processing command, the process proceeds to step S6. Then, it is determined whether or not the time difference is shorter than the transfer time of the minimum transfer size. That is, when there is no great difference in the reception time of the processing command from the data transfer time of one unit, the process proceeds to step S7, and the process with the higher priority is transferred first. When the difference between the reception times of the processing commands is relatively large, the process proceeds to step S8, and the setting is performed such that the one who received the command first is processed first. On the other hand, if there is a processing command accepted at the same time, the process proceeds from step S5 to step S9, and the priority bit 20 is generated in the manner described above. Then, in step S10, the priority bits corresponding to each processing command are compared. Then, the one with the higher priority bit, that is, the one with the higher priority is set to be transferred first, and the one with the lower priority bit is set to be transferred later (steps S11 and S12). As described above, it is possible to optimize the scheduling in which the reproduction process and the retransmission process having the highest priority are preferentially executed and the priority for ensuring the transfer rate according to the size of the buffer memory is added.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a configuration of a scheduler of a media server of the present invention.

FIG. 2 is a block diagram of the entire system.

FIG. 3 is a conceptual diagram of a data transfer operation.

FIG. 4 is an operation flowchart of a scheduler.

[Explanation of symbols]

 1 Main processing unit 2 Time monitoring unit 3 Data transfer unit 4 Priority calculation unit 5 Player 20 Priority bit

Claims (2)

[Claims] 1. A method for receiving a processing command including data transfer requests from a plurality of players, reading the data from a storage medium, and performing data transfer and execution scheduling of the processing command that require real-time processing. , A main body processing unit that receives a processing command from each player, and a priority corresponding to the type of the processing command is set, and a higher priority is set as the buffer memory provided in the requesting player is smaller. Then, when the priority setting means for determining the priority obtained by correcting the priority of the processing command and the reception of a plurality of processing commands compete with each other, the data transfer section for executing the data transfer in order from the data transfer request having the higher priority. With Scheduler of media servers that butterflies. 2. The priority setting means generates a priority bit indicating the priority for each data transfer for one time corresponding to each received processing command, and transfers the data in accordance with the display of the priority bit. Controlling the priority bit, a processing command is assigned to each upper bit in order of higher priority, and a complement to the buffer memory capacity of the requesting player is assigned to the lower bit. The scheduler of the media server described in 1.