Video optimized media streamer having communication nodes received digital data from storage node and transmitted said data to adapters

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CROSS REFERENCE TO RELATED PATENT APPLICATIONS

This application is related to the following U.S. patent applications.

Ser. No. 08/302,625, filed Sep. 8, 1994, entitled "Video Optimized Media Streamer", Inventors: W. R. Belknap et al.;

Ser. No. 08/302,626, filed Sep. 8, 1994, entitled "Video Optimized Media Streamer Data Flow Architecture", Inventors: M. Henley et al.;

Ser. No. 08/302,619, filed Sep. 8, 1994, entitled "Video Optimized Media Streamer with Cache Management", Inventors: W. R. Belknap et al.;

FIELD OF THE INVENTION

This invention relates to a system for delivery of multimedia data and, more particularly, an interactive video server system that provides video simultaneously to a plurality of terminals with minimal buffering.

BACKGROUND OF THE INVENTION

The playing of movies and video is today accomplished with rather old technology. The primary storage media is analog tape, such as VHS recorders/players, and extends up to the very high quality and very expensive D1 VTR's used by television studios and broadcasters. There are many problems with this technology. A few such problems include: the manual labor required to load the tapes, the wear and tear on the mechanical units, tape head, and the tape itself, and also the expense. One significant limitation that troubles Broadcast Stations is that the VTRs can only perform one function at a time, sequentially. Each tape unit costs from $75,000 to $150,000.

TV stations want to increase their revenues from commercials, which are nothing more than short movies, by inserting special commercials into their standard programs and thereby targeting each city as a separate market. This is a difficult task with tape technology, even with the very expensive Digital D1 tape systems or tape robots.

Traditional methods of delivery of multimedia data to end users fall into two categories: 1) broadcast industry methods and 2) computer industry methods. Broadcast methods (including motion picture, cable, television network, and record industries) generally provide storage in the form of analog or digitally recorded tape. The playing of tapes causes isochronous data streams to be generated which are then moved through broadcast industry equipment to the end user. Computer methods generally provide storage in the form of disks, or disks augmented with tape, and record data in compressed digital formats such as DVI, JPEG and MPEG. On request, computers deliver non-isochronous data streams to the end user, where hardware buffers and special application code smooths the data streams to enable continuous viewing or listening.

Video tape subsystems have traditionally exhibited a cost advantage over computer disk subsystems due to the cost of the storage media. However, video tape subsystems have the disadvantages of tape management, access latency, and relatively low reliability. These disadvantages are increasingly significant as computer storage costs have dropped, in combination with the advent of the real-time digital compression/decompression techniques.

Though computer subsystems have exhibited compounding cost/performance improvements, they are not generally considered to be "video friendly". Computers interface primarily to workstations and other computer terminals with interfaces and protocols that are termed "non-isochronous". To assure smooth (isochronous) delivery of multimedia data to the end user, computer systems require special application code and large buffers to overcome inherent weaknesses in their traditional communication methods. Also, computers are not video friendly in that they lack compatible interfaces to equipment in the multimedia industry which handle isochronous data streams and switch among them with a high degree of accuracy.

With the introduction of the use of computers to compress and store video material in digital format, a revolution has begun in several major industries such as television broadcasting, movie studio production, "Video on Demand" over telephone lines, pay-per-view movies in hotels, etc. Compression technology has progressed to the point where acceptable results can be achieved with compression ratios of 100.times. to 180.times.. Such compression ratios make random access disk technology an attractive alternative to prior art tape systems.

With an ability to random access digital disk data and the very high bandwidth of disk systems, the required system function and performance is within the performance, hardware cost, and expendability of disk technology. In the past, the use of disk files to store video or movies was never really a consideration because of the cost of storage. That cost has seen significant reductions in the recent past.

For the many new emerging markets that utilize compressed video data, using MPEG standards, there are several ways in which video data can be stored in a cost effective manner. This invention provides a hierarchical solution to many different performance requirements and results in a modular systems approach that can be customized to meet market requirements.

SUMMARY OF THE INVENTION

The invention provides a "video friendly" computer subsystem which enables isochronous data stream delivery in a multimedia environment over traditional interfaces for that industry. A media streamer in accordance with the invention is optimized for the delivery of isochronous data streams and can stream data into new computer networks with ATM (Asynchronous Transfer Mode) technology. This invention eliminates the disadvantages of video tape while providing a VTR (video tape recorder) metaphor for system control. The system of this invention provides the following features: scaleability to deliver from 1 to 1000's of independently controlled data streams to end users; an ability to deliver many isochronous data streams from a single copy of data; mixed output interfaces; mixed data rates; a simple "open system" control interface; automation control support; storage hierarchy support; and low cost per delivered stream.

A media streamer in accordance with this invention is comprised of at least one control node; at least one storage node for storing a digital representation of a video presentation; and a plurality of communication nodes each having an input port that is switchably under the direction of the at least one control node to an output of the at least one storage node for receiving a digital representation of a video presentation therefrom. Each of the plurality of communication nodes further includes at least one output port for coupling to a first end of a communications bus. Individual ones of the communication nodes output a digital representation of a video presentation as a sequence of data bursts to the first end of the communications bus. The media streamer further includes an adapter, coupled to a second end of the communications bus, for receiving the sequence of data bursts and for converting the received sequence of data bursts to a substantially isochronous data stream that represents a video presentation. The adapter comprises a data buffer having an input coupled to the second end of the communications bus and an output for providing the substantially isochronous data stream. The adapter further comprises a first converter having an input coupled to the output of the data buffer for converting the substantially isochronous data stream to a video compatible output signal. A second converter may also be provided, the second converter having an input coupled to the output of the data buffer for converting the substantially isochronous data stream to an audio compatible output signal.

The data buffer is comprised of a first data buffer having an input coupled to the second end of the communications bus and an output, the first data buffer having a storage capacity of X bytes; and a second data buffer having an input coupled to the output of the first data buffer and an output providing the substantially isochronous data stream, the second data buffer having a storage capacity of less than X bytes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a media streamer incorporating the invention hereof;

FIG. 1A is a block diagram which illustrates further details of a circuit switch shown in FIG. 1;

FIG. 1B is a block diagram which illustrates further details of a tape storage node shown in FIG. 1;

FIG. 1C is a block diagram which illustrates further details of a disk storage node shown in FIG. 1;

FIG. 1D is a block diagram which illustrates further details of a communication node shown in FIG. 1;

FIG. 2 illustrates a list of video stream output control commands which are executed at high priority and a further list of data management commands which are executed at lower priority;

FIG. 3 is a block diagram illustrating communication node data flow;

FIG. 4 is a block diagram illustrating disk storage node data flow;

FIG. 5 illustrates control message flow to enable a connect to be accomplished;

FIG. 6 illustrates control message flow to enable a play to occur;

FIG. 7 illustrates interfaces which exist between the media streamer and client control systems;

FIG. 8 illustrates a display panel showing a plurality of "soft" keys used to operate the media streamer;

FIG. 9 illustrates a load selection panel that is displayed upon selection of the load soft key on FIG. 8;

FIG. 10 illustrates a batch selection panel that is displayed when the batch key in FIG. 8 is selected;

FIG. 11 illustrates several client/server relationships which exist between a client control system and the media streamer;

FIG. 12 illustrates a prior art technique for accessing video data and feeding it to one or more output ports;

FIG. 13 is a block diagram indicating how plural video ports can access a single video segment contained in a communications node cache memory;

FIG. 14 is a block diagram illustrating how plural video ports have direct access to a video segment contained in cache memory on the disk storage node;

FIG. 15 illustrates a memory allocation scheme employed by the invention hereof;

FIG. 16 illustrates a segmented logical file for a video 1;

FIG. 17 illustrates how the various segments of video 1 are striped across a plurality of disk drives;

FIG. 18 illustrates a prior art switch interface between a storage node and a cross bar switch;

FIG. 19 illustrates how the prior art switch interface shown in FIG. 18 is modified to provide extended output bandwidth for a storage node;

FIG. 20 is a block diagram illustrating a procedure for assuring constant video output to a video output bus;

FIG. 21 illustrates a block diagram of a video adapter used in converting digital video data to analog video data;

FIG. 22 is a block diagram showing control modules that enable SCSI bus commands to be employed to control the video adapter card of FIG. 21.

DETAILED DESCRIPTION OF THE INVENTION

GLOSSARY

In the following description, a number of terms are used that are described below:

______________________________________ AAL-5 ATM ADAPTATION LAYER-5: Refers to a class of ATM service suitable for data transmission. ATM ASYNCRHONOUS TRANSFER MODE: A high speed switching and transport technology that can be used in a local or wide area network, or both. It is designed to carry both data and video/audio. Betacam A professional quality analog video format. CCIR 601 A standard resolution for digital television. 720 .times. 840 (for NTSC) or 720 .times. 576 (for PAL) liminance, with chrominance subsampled 2:1 horizontally. CPU CENTRAL PROCESSING UNIT: In computer architecture, the main entity that processes computer instructions. CRC CYCLIC REDUNDANCY CHECK. A data error detection scheme. D1 Digital Video recording format conforming to CCIR 601. Records on 19 mm video tape. D2 Digital video recording format conforming to SMPTE 244 M. Records on 19 mm video tape. D3 Digital Video recording format conforming to SMPTE 244 M. Records on 1/2" video tape. DASD DIRECT ACCESS STORAGE DEVICE: Any on-line data storage device or CD-ROM player that can be addressed is a DASD. Used synonymously with magnetic disk drive. DMA DIRECT MEMORY ACCESS: A method of moving data in a computer architecture that does not require the CPU to move the data. DVI A relatively low quality digital video compression format usually used to play video from CD-ROM disks to computer screens. E1 European equivalent of T1. FIFO FIRST IN FIRST OUT: Queue handling method that operates on a first-come, first-served basis. GenLock Refers to a process of synchronization to another video signal. It is required in computer capture of video to synchronize the digitizing process with the scanning parameters of the video signal. I/O INPUT/OUTPUT Isochronous Used to describe information that is time sensitive and that is sent (preferably) without interruptions. Video and audio data sent in real time are isochronous. JPEG JOINT PHOTOGRAPHIC EXPERT GROUP: A working committee under the auspices of the International Standards Organization that is defining a proposed universal standard for digital compression of still images for use in computer systems. KB KILO BYTES: 1024 bytes. LAN LOCAL AREA NETWORK: High-speed transmission over twisted pair, coax, or fiber optic cables that connect terminals, computers and peripherals together at distances of about a mile or less. LRU LEAST RECENTLY USED MPEG MOVING PICTURE EXPERTS GROUP: A working committee under the auspices of the International Standards Organization that is defining standards for the digital compression/decompression of motion video/audio. MPEG-1 is the initial standard and is in use. MPEG-2 will be the next standard and will support digital, flexible, scaleable video transport. It will cover multiple resolutions, bit rates and delivery mechanisms. MPEG-1, MPEG-2 See MPEG MRU MOST RECENTLY USED MTNU MOST TIME TO NEXT USE NTSC format NATIONAL TELEVISION STANDARDS COMMITTEE: The color television format that is the standard in the United States and Japan. PAL format PHASE ALTERNATION LINE: The color television format that is the standard for Europe except for France. PC PERSONAL COMPUTER: A relatively low cost computer that can be used for home or business. RAID REDUNDANT ARRAY of INEXPENSIVE DISKS: A storage arrangement that uses several magnetic or optical disks working in tandem to increase bandwidth output and to provide redundant backup. SCSI SMALL COMPUTER SYSTEM INTERFACE: An industry standard for connecting peripheral devices and their controllers to a computer. SIF SOURCE INPUT FORMAT: One quarter the CCIR 601 resolution. SMPTE SOCIETY OF MOTION PICTURE & TELEVISION ENGINEERS. SSA SERIAL STORAGE ARCHITECTURE: A standard for connecting peripheral devices and their controllers to computers. A possible replacement for SCSI. T1 Digital interface into the telephone network with a bit rate of 1.544 Mb/sec. TCP/IP TRANSMISSION CONTROL PROTOCOL/INTERNET PROGRAM: A set of protocols developed by the Department of Defense to link dissimilar computers across networks. VHS VERTICAL HELICAL SCAN: A common format for recording analog video on magnetic tape. VTR VIDEO TAPE RECORDER: A device for recording video on magnetic tape. VCR VIDEO CASSETTE RECORDER: Same as VTR. ______________________________________

A. GENERAL ARCHITECTURE

A video optimized stream server system 10 (hereafter referred to as media streamer) is shown in FIG. 10 and includes four architecturally distinct components to provide scaleability, high availability and configuration flexibility. The major components follow:

1) Low Latency Switch 12: a hardware/microcode component with a primary task of delivering date and control information between Communication Nodes 14, one or more Storage Nodes 16, 17 and one or more Control Nodes 18.

2) Communication Node 14: a hardware/microcode component with the primary task of enabling the "playing"(delivering data isochronously) or "recording"(receiving data isochronously) over an externally defined interface usually familiar to the broadcast industry: NTSC, PAL, D1, D2, etc. The digital-to-video interface is embodied in a video card contained in a plurality of video ports 15 connected at the output of each communication node 14.

3) Storage Node 16, 17: a hardware/microcode component with the primary task of managing a storage medium such as disk and associated storage availability options.

4) Control Node 18: a hardware/microcode component with the primary task of receiving and executing control commands from an externally defined subsystem interface familiar to the computer industry.

A typical media streamer with 64 nodes implementation might contain 31 communication nodes, 31 storage nodes, 2 control nodes interconnected with the low latency switch 12. A smaller system might contain no switch and a single hardware node that supports communications, storage and control functions. The design of media streamer 10 allows a small system to grow to a large system in the customer installation. In all configurations, the functional capability of media streamer 10 can remain the same except for the number of streams delivered and the number of multimedia hours stored.

In FIG. 1A, further details of low latency switch 12 are shown. A plurality of circuit switch chips (not shown) are interconnected on crossbar switch cards 20 which are interconnected via a planar board (schematically shown). The planar and a single card 20 constitute a low latency crossbar switch with 16 node ports. Additional cards 20 may be added to configure additional node ports and, if desired, active redundant node ports for high availability. Each port of the low latency switch 12 enables, by example, a 25 megabyte per second, full duplex communication channel.

Information is transferred through the switch 12 in packets. Each packet contains a header portion that controls the switching state of individual crossbar switch points in each of the switch chips. The control node 18 provides the other nodes (storage nodes 16, 17 and communication nodes 14) with the information necessary to enable peer-to-peer operation via the low latency switch 12.

In FIG. 1B, internal details of a tape storage node 17 are illustrated. As will be hereafter understood, tape storage node 17 provides a high capacity storage facility for storage of digital representations of video presentations.

As employed herein a video presentation can include one or more images that are suitable for display and/or processing. A video presentation may include an audio portion. The one or more images may be logically related, such as sequential frames of a film, movie, or animation sequence. The images may originally be generated by a camera, by a digital computer, or by a combination of a camera and a digital computer. The audio portion may be synchronized with the display of succesive images. As employed herein a data representation of a video presentation can be any suitable digital data format for representing one or more images and possibly audio. The digital data may be encoded and/or compressed.

Referring again to FIG. 1B a tape storage node 17 includes a tape library controller interface 24 which enables access to multiple tape records contained in a tape library 26. A further interface 28 enables access to other tape libraries via an SCSI bus interconnection. An internal system memory 30 enables a buffering of video data received from either of interfaces 24 or 28, or via DMA data transfer path 32. System memory block 30 may be a portion of a PC 34 which includes software 36 for tape library and file management actions. A switch interface and buffer module 38 (used also in disk storage nodes 16, communication nodes 14, and control nodes 18) enables interconnection between the tape storage node 17 and low latency switch 12. That is, the module 38 is responsible for partitioning a data transfer into packets and adding the header portion to each packet that the switch 12 employs to route the packet. When receiving a packet from the switch 12 the module 38 is responsible for stripping off the header portion before locally buffering or otherwise handling the received data.

Video data from tape library 26 is entered into system memory 30 in a first buffering action. Next, in response to initial direction from control node 18, the video data is routed through low latency switch 12 to a disk storage node 16 to be made ready for substant