System and process for delivering digital data on demand

• US 5,928,327 A
• Filed: 08/08/1996
• Issued: 07/27/1999
• Est. Priority Date: 08/08/1996
• Status: Expired due to Term

• Current Assignee: nSTREAMS Technologies, Inc.
• Original Assignee: nSTREAMS Technologies, Inc.
• Inventors: Hsu, Ching-San, Wang, Pong-sheng
• Primary Examiner(s): HSIA, SHERRIE Y
• Application Number:
  US08/692,697
• Time in Patent Office: 1,083 Days
• Field of Search: 348/6, 348/7, 348/12, 348/13, 395/200.47, 395/200.48, 395/200.49, 455/4.2, 455/5.1
• US Class Current: 725/88
• CPC Class Codes: H04N 7/17336 Handling of requests in head-ends

Abstract

A video server system and method has a modular and expandable system design to deliver a plurality of video streams on user demand and under user control. The video server system and method has a central control module adapted to receive control commands such as SELECT, PLAY, REWIND, PAUSE etc. to select and playback a video from a plurality of videos stored in a storage module. The central control module is a computer motherboard having a first small computer serial interface (SCSI) coupled to the storage device. The central control module also has memory for buffering data blocks of video retrieved from the storage device or devices prior to delivery to the delivery module also included in the system. The delivery module is also a computer motherboard having memory and also having a plurality of video processors for processing the video data prior to coupling the data to a client location. The delivery module additionally has a SCSI interface configured to operate in a target mode so that the central control module transfers video data to the delivery module in the same manner that it would use if it were writing to a conventional SCSI disk drive.

Claims

1. A video server system for servicing video clients, comprising:

a mass storage module configured to store a plurality of video selections;

a delivery module having a SCSI interface operating in a target mode thereby emulating a SCSI device, the delivery module having one or more processing modules, each for processing video data for delivery to a video client wherein the delivery module is programmed for receiving video data over the SCSI interface, buffering the received video data and delivering the buffered video data to a client,

the delivery module further including a first processor for controlling the transfers of video data to the one or more processing modules; and

a central control module having a first SCSI interface coupled to the mass storage module and a second SCSI interface coupled to the delivery module, the central control module programmed for receiving video control commands from a client and controlling the playback of the video selections responsive to the received control commands,

the central control module further including;

at least one memory buffer for receiving video data from the mass storage module and for buffering video data prior to transfer to the delivery module, and a second processor for controlling the transfer of video data from the mass storage module to the at least one memory buffer and from the at least one memory buffer to the delivery module.

2. The system of claim 1 wherein at least one processing module included in the delivery module is a video data decompressor for decompressing compressed video data.

3. The system of claim 2 wherein the video data decompressor performs data decompression in accordance with a Motion Picture Expert Group (MPEG) standard.

4. The system of claim 1 wherein the delivery module is a computer motherboard mounted in a rack-mountable chassis and the central control module is a computer motherboard mounted in a rock-mountable chassis.

5. The system of claim 1 wherein at least one processing module included in the delivery module is an ethernet formatting module for formatting the video data for delivery over an ethernet network.

6. The system of claim 1 wherein at least one processing module included in the delivery module is an asynchronous transfer mode (ATM) module for formatting the video data for delivery over an ATM network.

7. The system of claim 1 further comprising one or more additional delivery modules and wherein:

the mass storage module includes a plurality of SCSI-compatible storage devices; and

the central control module has a first plurality of SCSI interfaces coupled to the mass storage device and a second plurality of SCSI interfaces, each coupled to one or more delivery modules.

8. The system of claim 1 wherein the video selections each include control data and video data and wherein the control data is stored using a file management system associated with an operating system running on the central control module and wherein the video data is stored in a raw format bypassing the file management system.

9. The system of claim 8 wherein the control data includes a first address map indicating the address of unused memory on a storage device and a second address map mapping each data block of a video object to an address on the storage device.

10. The system of claim 1 wherein the central control module generates a plurality of read requests to read video data stored on the mass storage module and wherein the system of claim 1 further comprises:

a message queue for storing the read requests; and

a prioritizer operatively coupled to the message queue for prioritizing the read requests.

11. The system of claim 10 wherein the prioritizer performs a method comprising:

determining whether each read request is an urgent read request;

calculating a deadline for each urgent read request;

determining whether servicing a non-urgent read request will cause any urgent read request to miss a deadline;

responsive to determining that servicing a non-urgent read request will not cause any urgent read request to miss a deadline, servicing a non-urgent read request; and

responsive to determining that servicing a non-urgent read request will cause an urgent read request to miss a deadline, servicing a read request with an urgent deadline.

12. The system of claim 1 wherein:

the mass storage module includes a plurality of storage devices;

a plurality of the video selections are stored in a striping arrangement across the plurality of the storage devices; and

the controlling the playback of the video selections responsive to the received control commands comprises;

defining a plurality of time slots; and

identifying one of the storage devices from which playback is to commence and scheduling the playback of a video selection in a first available time slot associated with the identified storage device wherein each storage device rotates through servicing the plurality of time slots.

13. The system of claim 1 wherein:

the mass storage module includes a plurality of storage devices;

at least one video selection includes a plurality of data blocks and is stored in a striping arrangement across the plurality of the storage devices; and

the system further comprises;

an error block computed for every M data block wherein M is an integer redundancy factor less than the number of storage devices used in the striping arrangement.

17. The video server system of claim 1, further comprising:

a plurality of threads generated and executed by the central control module;

wherein the plurality of threads includes;

a remote procedure call thread for managing the interface between the video server system and the video clients;

at least one stream thread for managing a playback of a single video stream formed by the video data;

a callback thread for handling messages generated by the at least one stream thread, the messages indicating error conditions, and alternatively, indicating an end of a video file that includes the video data;

a plurality of storage threads for performing access and data retrieval functions on the mass storage module; and

a file thread for handling file management functions.

18. The video server system of claim 1, further comprising:

a first data bus coupled between the mass storage module and the first SCSI interface in the central control module; and

a second data bus coupled between the second SCSI interface in the central control module and the delivery module.

14. In a video server system adapted to receive a plurality of control commands including time critical commands and non-time critical commands, a method of prioritizing the service of the received control commands comprising:

determining a time deadline for each time critical command;

determining whether a non-time critical command can be serviced without causing any time critical command to miss an associated time deadline;

responsive to determining that the non-time critical command can be serviced without causing any time critical command to miss the associated time deadline, servicing a non-time critical, command; and

responsive to determining that a time critical command can not be serviced without causing any time critical command to miss the associated time deadline, servicing a time critical command.

15. A video server system for servicing video clients, comprising:

a mass storage module configured to store a plurality of video selections;

a delivery module having a SCSI interface operating in a target mode thereby emulating a SCSI device, the delivery module having one or more processing modules, each for processing video data for delivery to a video client wherein the delivery module is programmed for receiving video data over the SCSI interface, buffering the received video data and delivering the buffered video data to a client; and

a central control module having a first SCSI interface coupled to the mass storage module and a second SCSI interface coupled to the delivery module, the central control module programmed for receiving video control commands from a client and controlling the playback of the video selections responsive to the received control commands;

wherein at least one processing module included in the delivery module is an ethernet formatting module for formatting the video data for delivery over an ethernet network.

16. A video server system for servicing video clients, comprising:

a mass storage module configured to store a plurality of video selections;

a delivery module having a SCSI interface operating in a target mode thereby emulating a SCSI device, the delivery module having one or more processing modules, each for processing video data for delivery to a video client wherein the delivery module is programmed for receiving video data over the SCSI interface, buffering the received video data and delivering the buffered video data to a client; and

a central control module having a first SCSI interface coupled to the mass storage module and a second SCSI interface coupled to the delivery module, the central control module programmed for receiving video control commands from a client and controlling the playback of the video selections responsive to the received control commands;

wherein the mass storage module includes a plurality of storage devices;

wherein at least one video selection includes a plurality of data blocks and is stored in a striping arrangement across the plurality of the storage devices; and

wherein the system further comprises;

an error block computed for every M data block wherein M is an integer redundancy factor less than the number of storage devices used in the striping arrangement.