Real time stream server for handling a plurality of real time stream data with different data rates

• US 5,938,734 A
• Filed: 09/12/1996
• Issued: 08/17/1999
• Est. Priority Date: 09/12/1995
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kanai, Tatsunori, Maeda, Seiji, Yao, Hiroshi, Kizu, Toshiki
• Primary Examiner(s): Asta, Frank J.
• Assistant Examiner(s): VU, THONG H
• Application Number:
  US08/715,371
• Time in Patent Office: 1,069 Days
• Field of Search: 395/200.09, 395/200.08, 395/497.04, 395/191, 395/182.04, 395/800, 370/474, 370/466, 370/61, 709/232, 709/201, 709/231, 345/439, 386/95
• US Class Current: 709/232
• CPC Class Codes: H04N 21/2326 Scheduling disk or memory reading operations
• CPC Class Codes: H04N 7/17336 Handling of requests in head-ends

Abstract

A real time stream server capable of realizing a supply of a plurality of real time stream data with different data rates by a scheduling scheme using constant time-slot interval and transfer start timing period. A number of unit streams to be used and a block transfer time for each real time stream data are determined according to a data rate of each real time stream data. Each real time stream data is divided into a plurality of blocks, each block being in a size to be transferred within the block transfer time, and the blocks are sequentially distributed among the unit streams to be used. The blocks of each unit stream data are sequentially stored into a plurality of disk devices. In response to a request for each real time stream data from a client, the blocks constituting each real time stream data are read out from disk devices to a buffer memory, and each real time stream data is read out from a buffer memory and transferred to the client through a network, according to an appropriately scheduled transfer start timing for each unit stream.

Claims

1. A real time stream server, comprising:

a receiving unit for receiving real time stream data to be stored in the real time stream server;

a determining unit, communicatively coupled to the receiving unit, for determining a number of unit streams to be used according to a data rate of the real time stream data, each unit stream being defined as a stream which is scheduled by using at least a prescribed block transfer period T, and for determining a block transfer time for the real time stream data according to the number of unit streams to be used and the prescribed block transfer period T;

a dividing unit, communicatively coupled to the determining unit, for dividing the real time stream data into a plurality of blocks, each block being of a size to be transferred within the block transfer time, and sequentially distributing the blocks among as many unit streams as the number of unit streams to be used;

a plurality of disk devices for sequentially storing the blocks distributed among the unit streams;

a buffer memory, communicatively coupled to the plurality of disk devices, for temporarily storing the blocks read out from said plurality of disk devices; and

a transfer unit, communicatively coupled to the buffer memory, for transferring the real time stream data formed by the blocks read out from the buffer memory to a client through a network, using as many unit streams as the number of unit streams to be used in each block transfer period T.

2. The real time stream server of claim 1, wherein the control unit includes:

a management unit for managing a directory information for each real time stream data stored in said plurality of disk devices, the directory information indicating the number of unit streams to be used, a disk device ID number of a disk device which stores a top block of each unit stream, and a recording position of each block on a disk device which stores each block, for said each real time stream data.

3. The real time stream server of claim 2, wherein the control unit carries out operations with respect to each real time stream data according to the directory information for each real time stream data managed in the management unit.

4. The real time stream server of claim 1, wherein the control unit includes:

a scheduling unit for allocating stream resources for as many unit streams as the number of unit streams to be used, scheduling a transfer start timing for each unit stream in order to transfer the blocks continuously in a sequential order to form the real time stream data, and controlling the transfer unit to read out each block of each unit stream on the buffer memory within the block transfer time since the transfer start timing for each unit stream.

5. The real time stream server of claim 4, wherein the scheduling unit schedules the transfer start timing for each unit stream such that scheduled transfer start timings of the unit streams are displaced from one another by the block transfer time.

6. The real time stream server of claim 1, wherein each unit stream is defined as a stream which is scheduled by also using a prescribed block size L and a prescribed time-slot interval I.

7. The real time stream server of claim 1, wherein the determining unit detects a maximum data rate of the real time stream data, and determines the number m of unit streams to be used as a minimum integer which satisfies:

space="preserve" listing-type="equation">the maximum data rate≦

m×

R

where R is a prescribed maximum data rate of each unit stream.

8. The real time stream server of claim 7, wherein the determining unit determines the block transfer time as:

space="preserve" listing-type="equation">the block transfer time=T/m

where T is a prescribed block transfer period, and m is the number of unit streams to be used.

9. The real time stream server of claim 1, wherein the real time stream server has a capacity to supply Cmax sets of real time stream data with data rates not greater than R, where R is a prescribed maximum data rate of each unit stream, and the control unit sets a number of supplies Cm (m=1, 2, . . . ) to be allocated to each real time stream data with a data rate in a data rate range greater than (m-1)×

R and not greater than m×

R, arbitrarily within a range of;

##EQU3## where m is the number of unit streams to be used for said each real time stream data.

19. The real time stream server of claim 1, wherein each of the unit streams is a data stream at a prescribed reference data rate unit that is utilized internally within the real time stream server.

21. The real time stream server of claim 1, further comprising:

a control unit, communicatively coupled to the plurality of disk devices, for reading out the blocks constituting the real time stream data from said plurality of disk devices to the buffer memory, and reading out the real time stream data from the buffer memory, according to a request for real time stream data that has been sent from the client.

22. The real time stream server of claim 1, wherein the transfer unit sequentially transfers as many blocks as the number of unit streams to be used in each block transfer period T, each block being transferred within the block transfer time, such that the blocks are transferred continuously in a sequential order to form the real time stream data.

10. A method for operating a real time stream server having a plurality of disk devices and a buffer memory, comprising the steps of:

entering real time stream data into the real time stream server;

determining a number of unit streams to be used according to a data rate of the real time stream data, each unit stream being defined as a stream which is scheduled by using at least a prescribed block transfer period T, and determining a block transfer time for the real time stream data according to the number of unit streams to be used and the prescribed block transfer period T;

dividing the real time stream data into a plurality of blocks, each block being of a size to be transferred within the block transfer time, and sequentially distributing the blocks among as many unit streams as the number of unit streams to be used;

sequentially storing the blocks distributed among the unit streams into said plurality of disk devices; and

transferring the real time stream data formed by the blocks read out from the buffer memory to a client through a network, using as many unit streams as the number of unit streams to be used in each block transfer period T.

11. The method of claim 10, wherein the controlling step includes the step of:

managing a directory information for each real time stream data stored in said plurality of disk devices, the directory information indicating the number of unit streams to be used, a disk device ID number of a disk device which stores a top block of each unit stream, and a recording position of each block on a disk device which stores each block, for said each real time stream data.

12. The method of claim 11, wherein the controlling step carries out operations with respect to each real time stream data according to the directory information for each real time stream data managed by the management step.

13. The method of claim 10, wherein the controlling step includes steps of:

allocating stream resources for as many unit streams as the number of unit streams to be used;

scheduling a transfer start timing for each unit stream in order to transfer the blocks continuously in a sequential order to form the real time stream data; and

controlling the real time stream server to read out each block of each unit stream on the buffer memory within the block transfer time since the transfer start timing for each unit stream.

14. The method of claim 13, wherein the scheduling step schedules the transfer start timing for each unit stream such that scheduled transfer start timings of the unit streams are displaced one another by the block transfer time.

15. The method of claim 10, wherein each unit stream is defined as a stream which is scheduled by also using a prescribed block size L and a prescribed time-slot interval I.

16. The method of claim 10, wherein the determining step detects a maximum data rate of the real time stream data, and determines the number m of unit streams to be used as a minimum integer which satisfies:

space="preserve" listing-type="equation">the maximum data rate≦

m×

R

where R is a prescribed maximum data rate of each unit stream.

17. The method of claim 16, wherein the determining step determines the block transfer time as:

space="preserve" listing-type="equation">the block transfer time=T/m

where T is a prescribed block transfer period, and m is the number of unit streams to be used.

18. The method of claim 10, wherein the real time stream server has a capacity to supply Cmax sets of real time stream data with data rates not greater than R, where R is a prescribed maximum data rate of each unit stream, and the controlling step sets a number of supplies Cm (m=1, 2, . . . ) to be allocated to each real time stream data with a data rate in a data rate range greater than (m-1)×

R and not greater than m×

R, arbitrarily within a range of;

##EQU4## where m is the number of unit streams to be used for said each real time stream data.

20. The method of claim 10, wherein each of the unit streams is a data stream at a prescribed reference data rate unit that is utilized internally within the real time stream server.

23. The method of claim 10, further comprising the step of:

controlling the real time stream server to read blocks constituting the real time stream data from said plurality of disk devices to the buffer memory, and to read out the real time stream data from the buffer memory, according to a request for real time stream data from the client.

24. The method of claim 10, wherein the transferring step sequentially transfers as many blocks as the number of unit streams to be used in each block transfer period T, each block being transferred within the block transfer time, such that the blocks are transferred continuously in a sequential order to form the real time stream data.