Abstract:
A method of and apparatus for efficiently providing video on demand services to a cable television subscriber. The provider system consists of two major subsystems. The first subsystem, called a video server, streams video to video on demand subscribers through the cable television network. The second subsystem, called the transaction server, performs virtually all remaining provider functions including, security, accounting, storage and spooling of video data, etc. The video server is preferably uses a Unisys CMP memory platform into which the transaction server spools requested video programs. One or more industry standard processors operating under a standard operating system stream the video data from the memory platform to the subscriber.

Description:
CROSS REFERENCE TO CO-PENDING APPLICATIONS 
     This application is related to commonly assigned and co-pending U.S. patent application Ser. No. 09/304,406, filed May 4, 1999, and entitled “Video on Demand Transaction Server”; U.S. patent application Ser. No. 09/304,908, filed May 4, 1999, and entitled “Video On Demand System”; U.S. patent application Ser. No. 09/304,907, filed May 4, 1999, and entitled “Video on Demand Transaction Gateway”; and U.S. patent application Ser. No. 09/400,647, filed Sep. 21, 1999, and entitled “A Web Based Video on Demand Administration Application”, all of which are incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The pr sent invention generally relates to digital data transmission of video information and more particularly to the delivery of user selected video information to subscribing users. 
     2. Description of the Prior Art 
     The mass distribution of video programming signals (i.e., television) was originally accomplished primarily by the broadcasting of a very high frequency (i.e., VHF) carrier containing an amplitude modulated video signal and a frequency modulated audio signal. Through the addition of more broadcasting transmitters, a modest number of different programming signals could be simultaneously distributed to a large number of potential users with a modest capital commitment. Using this technique, the capital commitment increases almost linearly with number of different programming channels within the limits of the available spectrum space for separate and independent carriers. 
     Within a couple of decades, most of the scarce VHF spectrum space had been committed, and increasing demand for additional programming channels resulted in the allocation of spectrum space in the ultra-high frequency (i.e., UHF) region. Whereas virtually all receivers became UHF compatible, as a matter of policy, and UHF channels were assigned to requesters, it was appreciated that there were no economies of scale through the addition of more broadcast programming channels. 
     The cable television channel era was the result, wherein a capital commitment was required to wire each user home within a service area. As a result, about one hundred separate programming channels became readily available at a lesser cost than providing the same number of channels using conventional broadcast means. Initially, cable television was simply an analog system in which low power modulated carriers were transferred over a coaxial cable rather than being broadcast into the ether at substantially higher power levels. The cost saving was realized because the broadcasting was accomplished at substantially lower power. 
     With approximately one hundred different programming channels, it is typical to charge cable service user fees in accordance with a hierarchy of programming channels. The least expensive channels tend to be the preexisting broadcast channels and those cable channels supported primarily by advertisers which are intended for the most general audiences. The subscriber fees to access other channels increase as the programming becomes more specialized, advertising revenue becomes less likely to pay the programming costs, and the programming materials tend to have substantial economic value through other distribution channels. The so-called “premium channels” which show current and/or near current movies without advertising are typical of the higher cost programming options. 
     Most commercial cable television providers package the various programming channels into programming channel groups with different prices such that a given user can select a suitable programming package and pay the equivalent fee. Typically, a cable provider box, which couples the user television receiver to the coaxial cable source, is controlled by the cable television provider to give access to a given user to only those channels for which the appropriate subscriber fee has been paid. 
     The most expensive cable television channels currently available are “pay-per-view” or PPV. With the PPV concept, a given user can subscribe to a given programming channel for a single individual program of up to several hours for a separate subscriber fee. Typically, PPV channels provide sporting events and almost current movies. 
     Perhaps the major disadvantage of the PPV concept as currently implemented, is that the programming is provided in the “broadcast” mode. That means that the programming begins and runs on a predefined schedule. As a result, programming is missed if the user receives a telephone call, for example, during the viewing. Furthermore, it ordinarily requires the user to allocate viewing time to coincide with the predefined schedule. To overcome this disadvantage, many users rent video programs as video cassette recordings (i.e., VCR) from commercial stores which provide such a rental service. This permits the viewer to watch the program in accordance with her/his own schedule, stop the program during interruptions, and replay portions of the program which may not be readily understood. The primary disadvantage of the VCR rental approach is the need to physically go to the rental store to obtain the program and return to the rental store to return the recording. 
     With the capital commitment for cable television in place, their appear to be substantial new uses for the basic coaxial pathway. Such uses include, telephone, computer modem, facsimile, and video conferencing. To properly coordinate such diverse information transmission activities, attention is being directed to digital transmission schemes which provide for easier management of the distribution resources. U.S. Pat. No. 5,570,355, issued to Dail et al., discusses the handling of a number of diverse information transmissions within a single system. U.S. Pat. No. 5,673,265, issued to Gupta et al., U.S. Pat. No. 5,754,773, issued to Ozden et al., and U.S. Pat. No. 5,799,017, issued to Gupta et al., all discuss multi-media distribution systems. U.S. Pat. No. 5,555,244, issued to Gupta et al., is directed to multimedia distribution to residential users. 
     The digitization of video results in a great deal of data which must be transferred at a high rate to yield acceptable performance and resolution. By current standards, 3 mbits/sec. is considered to be a very acceptable rate. Such high data rates require systems which can provide high data rate transmission. U.S. Pat. No. 5,724,543, issued to Ozden et al., U.S. Pat. No. 5,699,362, issued to Makam, and U.S. Pat. No. 5,826,110, issued to Ozden et al., all concern themselves with high data rate retrieval and transmission. U.S. Pat. No. 5,675,573, issued to Karol et al., discusses the management of high data rate bandwidths. 
     In addition to retrieval and transmission of the required high data rates, there is also the need to provide high speed switching for switching as between data sources and destinations. U.S. Pat. No. 5,751,704, issued to Kostic et al., and U.S. Pat. No. 5,740,176, issued to Gupta et al., discuss high speed digital switching systems. 
     Whether it is data storage and retrieval, data transmission, or data switching, the fundamental technological problem associated with digital video results from the sheer volume of digitized video data and the tremendous rate at which it must be provided to the ultimate user for satisfactory performance. One technique for reduction of the volume problem is in reducing the resolution (and hence the volume of data) for those applications for which such reduction is acceptable. U.S. Pat. No. 5,623,308 and U.S. Pat. No. 5,691,768, both issued to Civanlar et al., directly address the handling of multiple resolution digitized video signals within a single system. 
     Notwithstanding attempts to reduce the resolutions to the lowest acceptable levels, the total data volume of any commercially useful system will remain high. The most common way to treat extremely high data volumes is through data compression. U.S. Pat. No. 5,710,829, issued to Chen et al., U.S. Pat. No. 5,742,343, issued to Haskell et al., and U.S. Pat. No. 5,619,256, issued to Haskell et are concerned with digital compression techniques. Specific attention to compression of digitized video is found in U.S. Pat. No. 5,764,803, issued to Jacquin et al. Compression of 3-dimensional images is treated by U.S. Pat. No. 5,612,735, issued to Haskell et al. 
     The evolving techniques of digitized video transmission have resulted in a transmission standard, called Asynchronous Transfer Mode (ATM). U.S. Pat. No. 5,668,841, issued to Haskell et al., describes data transmission using the ATM standard. An ATM converter is discussed in U.S. Pat. No. 5,809,022, issued to Byers et al. U.S. Pat. No. 5,724,349, issued to Cloonan et al., suggests an approach to packet switching within an ATM system. An ATM architecture is discussed in U.S. Pat. No. 5,781,320, issued to Byers. Interfacing to ATM systems is addressed in U.S. Pat. No. 5,842,111, issued to Byers. 
     A solution to the PPV problems noted above utilizing digitized video has been termed, Video on Demand (or VOD). In a VOD system, digitized video programming is made available to individual cable television subscribers in response to specific requests made by the user. U.S. Pat. No. 5,867,155, issued to Williams, describes the use of VOD for a very specialized application. Sea Change, International, has proposed a VOD approach for cable television subscribers. U.S. Pat. No. 5,583,561, issued to Baker et al., assigned to the assignee of the present invention and incorporated herein by reference, discloses and teaches a complete, modern VOD system employing a centralized architecture utilizing an enterprise server developed by Unisys Corporation. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes many of the disadvantages found within the prior art by providing a video on demand system which separates the tasks of supplying video to subscribers from the tasks associated with managing the subscriber interface. The key to this approach is to provide an architecture in which the necessary functions are divided into two separate portions. A first hardware and software subsystem, called a video server, is specifically dedicated to retrieving and transmitting the stream of video information. Virtually no other functions are performed by the video server. A second hardware and software subsystem, called the transaction server, handles virtually all other functions including control interface with the subscribers, spooling of digitized video data, subscriber accounting, etc. 
     The video server has two primary design criteria. First, it must be highly optimized to handle the extremely high input/output data rates. In essence, this is the sole function of the video server, and therefore, the design of the video server hardware and software are most directed towards this characteristic. Because the role of the video subsystem is simplified and single dimensional, video subsystems utilizing current technology can be produced at a surprisingly low cost. 
     The second major design criterion of the video server subsystem involves modularity. The addition of active subscribers, each viewing individual video programs (or the same program at different times), tends to increase the total input/output load of the video server subsystem linearly. Therefore, there is great economic incentive to design the video server subsystem in such a manner that the hardware resources to implement the video subsystem may be linearly increased in relatively small (and inexpensive) increments. 
     In the preferred mode of the present invention, the video server subsystem consists of a modularly expandable Unisys CMP memory platform. All video data is spooled into and streamed out of the memory installed in this platform. One or more input/output data rate optimized, industry compatible computers operating under a readily available, commercial operating system, such as Windows NT provide the simple timing and control functions. Using 3 mbits/second per video stream as a standard, each such device can effective service thousands of different and independent video streams. Within each video server, storage can be added to handle more video programs and communication interfaces can be added to provide more video streams. Therefore, the same design architecture and components are suitable for a wide range of system sizes, and the incremental capital cost to the video programming supplier can be readily determined as further subscribers are added to the system. 
     Unlike the video server subsystem which is optimized to provide a low cost, highly modular approach to a single function, the transaction server is optimized to provide a low cost approach to a wide and highly expandable variety of functions. In fact, all of the functions of the video on demand system, except for the video streaming function performed by the video server, are accomplished by the transaction server. Typical tasks include: transactional interface with the subscribers, subscriber fee accounting, requested program spooling, video server subsystem control, receiving video from a satellite and storing it in an archive, etc. Thus, the ideal hardware/software platform for implementation of the transaction server is a readily expandable, highly flexible, high availability, highly recoverable, realtime oriented mainframe system. In the preferred mode of the present invention, the Unisys 2200 is used to host the transaction server. 
     In accordance with the present invention, a subscribing user transfers a programming request to the transaction server. The transaction server makes the required subscriber accounting entry and notifies the corresponding preloaded video server platform of the new subscriber request. If the asset is not preloaded, in addition to the subscriber accounting, the transaction server must access the request video program and spool it for storage in the video server. Depending upon the rate of use of the requested video program, the data might be stored in memory (for high volume use), on a disk or other mass storage device (for medium volume use), or in some other medium (for low volume use). 
     In the preferred mode of the present invention, the user is permitted to pause, reverse, or fast forward the requested video program though commands entered from the on-set subscriber box. These functions are intended to appear similar to normal VCR commands to the user. These commands are sent to the transaction server which utilizes them to control the corresponding video stream output of the video server subsystem. Thus the user is provided with all of the advantages of VCR rental without the need to physically transport the medium (i.e., cassette tape) back and forth between the rental store and the user site. 
     In view of the power and flexibility of the transaction server, other diverse but somewhat related functions may be provided. For example, a user might order a pizza delivery via the on-set subscriber box to transaction server interface, or the user might access the internet, e-mail, or faxes via the transaction server. If this interface is implemented over a readily available, publicly accessible, network, such as the internet, many additional functions are possible. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects of the present invention and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which like reference numerals designate like parts throughout the figures thereof and wherein: 
         FIG. 1  is a schematic diagram showing the operation of the overall video on demand system of the present invention; 
         FIG. 2  is a schematic diagram showing spooling of the video programming data from typical mass storage devices; 
         FIG. 3  is a schematic diagram showing the generation of a video stream from spooled data within a memory subsystem; 
         FIG. 4  is a schematic diagram showing video streaming as synchronized on one minute boundaries; 
         FIG. 5  is a schematic diagram showing operation of a video server platform; 
         FIG. 6  is a schematic diagram showing video streaming of multiple programs from a single video server platform; 
         FIG. 7  is a schematic diagram showing video streaming from video programming data spooled on disk drive mass storage units; 
         FIG. 8  is a schematic diagram showing video streaming from video programming data stored on both disk drive mass storage units and memory subsystems; 
         FIG. 9  is a block diagram of a maximum configuration transaction server; 
         FIG. 10  is a detailed diagram of the operation of the transaction server of the preferred mode of the present invention; 
         FIG. 11  is a detailed functional diagram of the video on demand system; and 
         FIG. 12  is a detailed functional diagram of the video on demand appliance (VODA). 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a schematic diagram  10  showing the overall video on demand system of the present invention. A subscribing user (not shown) is positioned adjacent standard television receiver  34 . Through this television receiver, the user is capable of viewing video programming material transferred to his location via coaxial cable  30  from network  26  in the fashion currently known in the cable television industry. The interface between coaxial cable  30  and standard television receiver  34  is provided by subscriber box  32 , which provides the conversion between MPEG-2 digitized video format and the analog video signal required by television receiver  34 . 
     In many respects, subscriber box  32  is similar to the subscriber boxes utilized with existing cable television systems with the slight functional differences described in more detail below. The basic reason for these slight differences is to permit a subscribing user to communicate with transaction server  12  in a two directional manner. Not only does subscriber box  32  receive video programming data via coaxial cable  30  and present it to television receiver  34 , but subscriber box  32  is capable of transferring user requests via coaxial cable  30  and network  26  to transaction server  12  via path  28 . The most important requests in accordance with the present invention are those which initiate and control the individualized video on demand programming. 
     When the user is interested in viewing a particular video program, a request is made from subscriber box  32  and transferred to transaction server  12  via coaxial cable  30 , network  26 , and path  28 . Transaction server  12 , a Unisys 2200 server system in the preferred embodiment, is provided access to video programming information from satellite receiver  14 , from analog video storage  16  and digital mass storage  18 . In each instance, the video programming data is either received in digital form or converted to digital form. According to the preferred embodiment of the present invention, the MPEG-2 standardized format is utilized. 
     Whenever a request is received, transaction server  12  checks various security parameters, makes appropriate subscriber billing entries, and generally performs all of the necessary administrative functions as described below in greater detail. Additionally, transaction server  12  spools digital video data for transmission by the video server assigned to the requesting subscriber. One of video server platforms  20 ,  22 , . . . , or  24  is assigned the task by transaction server  12  and the spooled digital video data is supplied via the digital data bus shown. In the preferred mode of the present invention, each video server platform is a separate industry compatible, Windows NT based, computer platform. Once downloaded to the selected video server, the requested video programming is transmitted via network  26  and coaxial cable  30  to subscriber box  32  and television receiver  34 . 
       FIG. 2  is a schematic diagram showing the spooling of data from digital disk mass storage devices. For the preferred mode of the present invention, the digitized video programming data is stored in MPEG-2 format. In the spooling process, the MPEG-2 organized and placed into memory as a programming file  54 . To produce commercially acceptable video, 3 mbits/second is required. That means that a two hour video program requires the about 2.7 billion bytes of data storage. Because of cost considerations, many of the programs having low and moderate usage will best be stored on mass storage disk until requested 
     Individual storage disks  48 ,  50 , . . . , and  52  each store a number of video programs in MPEG-2 format. As requested, this data is transferred via storage bus  46  through disk control  42  through I/O bus  38  and placed in memory  55  via path  40 . A software program spools the data to the ATM interface  54  at the required speed. 
       FIG. 3  is a schematic diagram showing spooling of high volume digitized video program. For those programs having a high user demand, it is much more efficient to spool the program files from random access memory rather than mass storage disk systems. In this context, high volume means a high probability that the given program will be in use during high service volume periods. That means that there will need to be random access storage allocated to the storage of that given program during peak memory demand. As a result, the system should simply allocate random access storage to that given program. Very popular, recent movies are typical of such high volume programs. 
     If a program is a high volume program, it is preferably stored in auxiliary memory  56 . Upon request, software residing in memory  36  directs the spooling of data from auxiliary memory  56  and transferring it via path  40  and I/O bus  38  to ATM interface  54 . It should be noted that this is significantly more efficient than the spooling operation shown in  FIG. 2 , since the video data only needs to be read out of memory instead of having to be loaded from disk each time the data is used. Furthermore, there is no additional cost if a program is of sufficiently high volume that the required random access memory must be allocated to the program anyway. 
       FIG. 4  is a schematic diagram  58  showing the synchronization of a given video program around one minute time slots. In concept, the present invention provides subscribers with video on demand. However, as a practical matter, by synchronizing multiple users around one minute time slots, the maximum number of transmissions to all users of the given video program cannot exceed 60 per hour of programming and 120 for a two hour standard video program. That means that for a given high volume program (which may be requested by hundreds or even thousands within the length of time to view the program) each requester is assigned to an appropriate time slot. 
     First time slot  60  provides the first minute of video programming to one or more requesters. During one minute time slot  62 , the initial requesters receive the second minute of programming, and one or more requesters may be starting with the first minute of programming. At the nth time slot  64 , the initial requesters are viewing the nth minute of programming, the second group of requesters is viewing the n−1 minute of programming, and the nth group of requesters is viewing the first minute of programming. At final time slot  66 , the initial requesters are viewing the final minute of programming, the second group of requesters is viewing the second to last minute of programming, and a new group of requesters is viewing the initial minute of programming. 
     The reduction in total data requirements utilizing these one minute time slots is substantial. The total delay to a requester is no more than one minute and will average one half minute, making the process perfectly acceptable and barely noticeable to the subscribers. 
       FIG. 5  is a schematic diagram of a single industry compatible, Windows NT based video server platform. The video server subsystem is composed of a number of separate and largely independent video server platforms. Each is configured to have a maximum memory configuration and maximum I/O configuration. Digitized video programming data in the MPEG-2 format are spooled from transaction server  68  via interconnect  70  into the assigned video server platform. Program  74  and program  72  are shown. These programs are place onto network  78  under control of transmission control software  80  for transfer to the requesting subscriber(s). For a given program being sent to a single user, transmission control software  80  simply retrieves the video data from memory in a sequential fashion at 3 mbits/second and places it on network  78 . 
       FIG. 6  is a schematic diagram showing spooling of high volume program  82  into the video server platform of  FIG. 5 . The spooling is performed by the transaction server as discussed above. The spooled data is transferred to the video server platform via I/O bus  84  Up to ten programs can be stored and streamed from a single video server For simplicity, only one video server is shown. For a view of multiple video servers within a system, refer to  FIG. 1 . All other referenced elements are as previously described. 
       FIG. 7  is a schematic diagram showing the spooling of low to moderate volume digitized video program data. For lower volume programs, storage on disk storage mass memory may be appropriate. A low volume video program is one in which it is highly unlikely that more than one request is received during the runtime of the video program. Therefore, the servicing of the request is most probably an index sequential task for retrieving the data and transmitting it to the user. This is readily distinguishable from the high volume video programs for which transmissions within multiple and perhaps many of the one minute time slots is expected (see also  FIG. 4 ). These programs are spooled to the video server platform as shown. The remaining referenced elements are as previously described. 
       FIG. 8  is a schematic diagram showing spooling of low and high volume video programs to the same video server platform. All referenced elements are as previously described. 
       FIG. 9  is a block diagram  84  of the maximum configuration of the transaction server of the preferred mode of the present invention. In this preferred mode, the video server is implemented using a current model Unisys mainframe system. In accordance with this product, the system is expandable from a single processor, single main memory, and single I/O controller to the maximum system shown. 
     Instruction processors  102 ,  104 ,  106 ,  108 ,  110 ,  112 ,  114 , and  116  communicate with main memories  86 ,  88 ,  90 , and  92  via crossbar interconnects  94 ,  96 ,  98 , and  100 . Each instruction processor may be coupled with up to four third-level caches, as shown. Direct Input/Output bridges  118 ,  120 ,  122 ,  124 ,  126 ,  128 ,  130 , and  132  each handle video output functions. Each of the direct Input/Output bridges may be partitioned into separate partitions as shown. Additional description of partitioning may be found in U.S. patent application Ser. No. 08/779,472, filed Jan. 7, 1997, commonly assigned to the present invention and incorporated herein by reference. 
       FIG. 10  is a detailed functional diagram  134  of the transaction server. Communication with subscriber box  32  (see also  FIG. 1 ) is managed by set top management module  142 . Initial requests are selected by the user and honored through utilization of menu transaction module  140 . After initiation of the servicing of a given request, control of the matter is given to session manager  138  for completion. Any and all communication with the transaction server are monitored by security module  148 . Administration module  136  provides overall control of the transaction server. 
     The transaction server may be utilized to interface with the internet. The selected hardware and software system selected for the preferred mode provide internet server facilities in a commercially usable form. Video server session management module  146  provides the detailed functions (e.g., spooling of digital video programming) associated with the primary video on demand service. These control functions are directly interfaced to the video server subsystem via video server interface  150 . 
     Event logging module  154  journals the functions performed. This log is made available to digital network control services  152 . Media directory services and asset management module  162  provides long term control and asset management. Historical storage of these data is performed by asset storage management and asset capture. 
     In performing the actual video on demand service, the appropriate requested digitized video program is accessed from databases  160 . It is spooled by asset delivery, video streaming module  158 . The transfer is made via video server interface  156  (see also  FIG. 1 ). 
       FIG. 11  is a detailed functional diagram  166  of the entire video on demand system. Disk tape storage  168  retains the basic programming data. As explained above, only the very lowest usage frequency assets will be stored in analog form. The transaction gateway  170  is preferably housed within a Unisys HMP/IX 4800 mainframe system. 
     A request for a particular video on demand program is initiated by the user (not shown) at set-top subscriber box  190 . In the preferred mode, this request may be initiated by a wireless remote control in the manner known in the art and available from Scientific Atlanta or General Instruments. The request is transferred via the coaxial network or cable to quadrature amplitude modulation device  180 , available from either General Instruments or Scientific Atlanta. The request is transferred to transaction gateway  170  via pathway  184 . 
     The requested video on demand program is spooled from transaction gateway  170  to video on demand appliance  174  via messaging interface  172 , if available in disk/tape storage  168 . The requested video on demand program is streamed from video on demand appliance  174  via ATM network  176 , as described in more detail below. Multiplexer  180  combines the video on demand programming with other programming sources (e.g., broadcast) and supplies this combination to quadrature amplitude modulation device  180  for transmission to the set-top subscriber box  190  and television receiver  186 . 
       FIG. 12  is a detailed functional diagram of the operation of video on demand appliance, VODA,  174  (i.e., video server). Requested video programming is transferred to VODA  174  in MPEG-2 format via path  172 . Preferably, VODA  174  contains Unisys CMP memory platform  192  into which the digitized video data is spooled. The data is placed serially into memory such that program  194  is a memory storage area having a complete digital program stored in sequential order. Programs  196 ,  198 , and  200  are spooled into memory in a similar fashion. 
     Intel processors  204 ,  206 ,  208 ,  210 ,  212 , and  214  all have access to Unisys CMP memory platform  192  as shown. In the preferred mode, these processors operate under Windows NT and stream each of the video programs from Unisys CMP memory platform  192  to the user via path  176  (see also  FIG. 11 ). Streaming involves the timed access from memory of the serially stored program which produces the desired resolution in time and space. The preferred mode of the present invention is modularly expandable to stream thousands of separate video on demand programs. 
     Having thus describe the preferred embodiments in detail, those of skill in the art will be readily able to use the teachings found herein to make and use yet other embodiments within the scope of the claims appended hereto.