Networked Hyper QuickTime for Education-On-Demand Wei-hsiu Ma , Yen-Jen Lee1 , and David H.C. Du2 Distributed Multimedia Research Center3 Department of Computer Science University of Minnesota Mark P. McCahill Distributed Computing Services University of Minnesota Abstract It is generally recognized that the Internet can be used as a platform to deliver distance education services and that Internet information systems can be leveraged to enhance education . For instructors , the Internet provides shared access to resources and media-rich materials to augment traditional instruction . Much of the current educational use of Internet information systems is for publishing collections of documents and hypermedia links to other information . However , menubased hypermedia systems -LRB- Gopher -RRB- or document-based hypermedia -LRB- WWW -RRB- do not address the need for video-based hypermedia as method for delivering annotated presentations and lectures . Networked Hyper QuickTime -LRB- NHQT -RRB- is a prototype education-on-demand -LRB- EOD -RRB- system designed to deliver hypermedia annotated video over the Internet for low-cost desktop PC systems . NHQT uses WWW , Gopher , and QuickTime technologies to deliver video streams with embedded Uniform Resource Locators -LRB- URLs -RRB- pointing to ancillary documents or video streams . By incorporating URLs in video presentations , the users can follow hypermedia links to documents and video segments which are pertinent to the section of the video being viewed . NHQT 's video-based user interface supports a full range of user interactions , including VCR-style playback control , random positioning , content-based search , and automatic resolution of hypermedia links for Internet access . NHQT also provides easy-to-use authoring functions to embed annotations and hypermedia links into a video . A testbed of ATM network for Macintosh and workstation platforms has been built to study the future high speed network infrastructure with NHQT . 1 Introduction In recent years , the entire network computing paradigm has shifted from proprietary dialup services and local-area or campus-wide networks to the Internet . The exponential growth of the Internet has resulted in a large and growing number of people with access to the information and services available on the Internet . This convergence on the Internet as a standard vehicle for delivering information and the global nature of the Internet makes it very attractive for publishing . Instant access to globally distributed information has popularized hypermedia for on-line publishing , and it is likely that various 1Part of the work related to ATM on Macintosh was conducted while one of the authors was an intern in Advanced Technology Group , Apple Computer in summer , 1995 . 2This work is supported in part by NSF Grant CDA-9502979 and a gift from IBM . 3Distributed Multimedia Research Center -LRB- DMRC -RRB- is sponsored by US WEST , Honeywell , IVI Publishing , Computing Devices International , and Network Systems Corporation . forms of Internet mediated hypermedia will become a dominant form of publishing . Taking advantage of these trends to deliver distance education is one of the most exciting challenges for the existing educational institutions . Many people have limited access to the traditional classroom setting due to various constraints , such as , time , distance , physical disabilities , transportation limitations and expenses , or non-school commitments -LRB- e.g. children at home , job -RRB- -LSB- 1 -RSB- . Education-on-demand -LRB- EOD -RRB- system provides distance learning opportunities for continuing education . Even for traditional full-time students , distance learning can provide attractive options with great flexibility . However , the development of distance education over the Internet is still in its early stage for a variety of reasons . ffl The protocols and browsers for the most popular Internet information systems -LRB- Internet Gopher and World Wide Web -RRB- are designed to deliver static documents rather than full-motion video . While the links in Gopher directories and WWW pages demonstrate the power of Internet mediated hypermedia , the content of these document based systems is not designed to present presentation or lecture-based courseware . Navigating a series of documents is closer in spirit to reading a textbook than to atteding a course of lectures . ffl Network bandwidth is limited for end-users . This limitation restricts the development of attractive and media-rich learning tools , especially video delivery on the Internet . Of course , CD-ROMs can be used as a delivery mechanism for multimedia information , but this is static information unless it incorporates links to information available on the Internet . ffl There are system processing constraints for both end-users and service providers -LRB- or schools -RRB- . Most users can not afford workstations , so they buy and use PC-based machines . To deliver information to a broad base of users requires applications running on PC-based platforms . Most publishers also prefer to use low-cost hardware to author digitized lectures . ffl A busy instructor does not have time to learn complicated authoring tools to design and arrange the lecture . Publishers really need easy-to-use authoring tools to motivate instructors to help produce digital videos in short time . Unfortunately , tools for authoring video-based hypermedia on desktop PCs are not readily available today . ffl The digital videos should incorporate hypermedia links to related information so that viewing the video is not a completely passive activity . By annotating video with hypermedia links , the instructor could point to more in-depth and related information that the viewer may wish to explore in the same way that WWW links can point to related information . Given these problems , it is clear that there is a need for a simple , elegant tool to deliver lecture and presentation based education over the Internet . To address this need we have developed a prototype Education on Demand -LRB- EOD -RRB- system called Networked Hyper QuickTime -LRB- NHQT -RRB- . NHQT extends the functions of the current Internet and points to how distance education can take advantage of the Internet 's evolution in the next century . Our goal is to combine class lectures and Internet resources to provide an EOD distance education service . Our motivations and objectives include : ffl Create an EOD system over the Internet from which students can access courses and class materials by computers at remote sites on a flexible schedule . ffl Utilize the related materials and resources on the Internet in lectures . Extend learners ' view over the whole Internet . ffl Provide a video-based learning environment to integrate different media , such as audio , music , text , images and animation together to satisfy different educational purposes . This environment must be easy to operate and easy for users to control the progress of a lecture . ffl Design Network QuickTime -LRB- NQT -RRB- subsystem to provide lecture or media delivery over the Internet with low-bandwidth requirement instead of retrieving large files into local machine and save the local disk space . ffl Implement an EOD application on PC-based platform . Utilize the freely available Internet resources with component design methodology to reduce the system cost and complexity . ffl Provide an authoring tool so that instructors can create lectures and arrange different media into a lecture easily . Many schools and research groups are using World-Wide Web to construct distance education environments on the Internet based on Web browsers -LSB- 2 -RSB- -LSB- 3 -RSB- . These environments are basically confined by the traditional presentation of static documents . The users easily get lost after traversing many links if the materials are not organized well . NHQT provides video-based materials more like a lecture . It also transforms a linear media , such as a video of a lecture , into hypermedia by linking the lecture to other media . North Dakota State University and Cornell University have projects to create virtual classroom by integrating software on the Internet , such as news group , audio software and video conferencing -LSB- 4 -RSB- -LSB- 5 -RSB- . They emphasize the lecture in real time , but NHQT provides EOD service which means that a learner can request a stored lecture according to his schedule . Schnepf , etc. . presents a medical education environment over ATM -LRB- Asynchronous Transfer Mode -RRB- networks -LSB- 6 -RSB- which is used for a special educational purpose . NHQT is able to support various educational purposes , such as email training , medical , language or music education in light of its user interaction functionalities and media-rich environment . The organization of the paper is as follows . Section 2 provides the overview of the environment upon which NHQT is developed . Section 3 describes the whole system design in detail . Section 4 demonstrates various applications to which NHQT can be applied . Section 5 concludes the paper and discusses future work . 2 Environment Overview Figure 1 illustrates the three parts of the conceptual system architecture : end-users , network infrastructure and servers . The end-users retrieve information or resources from the servers through network infrastructure . This section covers the architecture and rationale for the environment upon which NHQT is built . The most important technologies in the NHQT architecture are QuickTime , World Wide Web , Internet Gopher , and ATM network . Because we are interested in a video centered Internet or ATM Clouds Lecture Streams or MaterialsRequests Network Infrastructure End Users Lecture Server End Users End Users Gopher Server Web Server Figure 1 : Environment of Education-on-Demand System medium , the majority of the display functions for NHQT are built on top of Apple 's QuickTime architecture . Rather than building full-featured WWW/Gopher browsers into the NHQT viewer , we take advantage of existing browsers to resolve URLs by sending external browsers a `` get this URL '' message when appropriate . The network infrastructure of NHQT is basically the Internet , which we expect to continue its evolution by embracing emerging high-speed networks based on ATM . To explore how the system could work over future high-bandwidth networks , we built an ATM testbed network using a Macintosh as the user workstation to assimilate the high-speed network infrastructure . The following subsections discuss these enabling technologies in further detail . 2.1 QuickTime QuickTime is a technology developed by Apple Computer for time-based media on Macintosh and PC-based platforms -LSB- 7 -RSB- . Apple 's QuickTime system extension provides a set of functions and data structures for applications to edit , save , display , and control QuickTime movies . For NHQT , the most important feature of QuickTime is that movie may contain several logical tracks which are synchronized . Each track refers to a media such as text , image , audio or video , so there is room in the QuickTime data architecture for application-defined data to be carried along with audio/video stream . QuickTime supports a variety of compression and decompression schemes including MPEG-1 , MPEG-2 and several software-based codecs . To support MPEG video , QuickTime requires a hardware codec in user 's machine and higher network bandwidth to meet stringent playback requirements . However , since the QuickTime architecture insulates the application program for dealing with the specific compression scheme , an application written to the QuickTime API does not need to be modified to take advantage of any of the supported compression schemes . We chose QuickTime as our basic video architecture because : -LRB- 1 -RRB- The standard QuickTime software codec is freely available on Macintosh and 80x86-based PC platforms . -LRB- 2 -RRB- QuickTime has low bandwidth requirements -LRB- an important consideration for video delivery over the Internet -RRB- . -LRB- 3 -RRB- QuickTime 's multiple track data architecture can support many media types including text , images , audio , MIDI , animation and video . -LRB- 4 -RRB- Our application is not required to provide a synchronization mechanism for playback . -LRB- 5 -RRB- The QuickTime software architecture is extensible , which is critical in development phase and in preserving user investment . Internally , QuickTime consists of software modules -LRB- components -RRB- , each of which provides a defined set of services . These components take the responsibilities for tasks such as user interface , video de - Movie Toolbox Video Media Handler Sound Media Handler Data Handler Sound ManagerCompression Image Manager Image Compression Component QuickDraw Application Sound Ouput Movie Data QuickTime Video Output Data Flow Figure 2 : Software Modules of QuickTime for Movie Display compression , manipulating media , etc. . Figure 2 illustrates the architecture of the components involved when QuickTime displays a movie with a video and an audio tracks . Movie Toolbox receives the function calls from application and calls the related components in next level to continue the process of the function calls . Video media handler and sound media handler handle video and audio media , respectively . They send data requests to data handler which does the actual reading and writing of media data . This modular internal architecture makes it possible to replace the standard data handler with network-aware data handlers . Our Network QuickTime client module contains a novel data handler which is able to deal with the data in local disk or through network . Thus QuickTime provides us with a place to store annotations -LRB- text or URLs -RRB- in alternate tracks and provides us with an architecture that can accommodate both reading digital videos from a local hard disk or from a networked video server . 2.2 Internet Gopher and World Wide Web In the early days of the Internet , information was typically published as text documents . Two popular first generation distributed Internet information systems -LRB- Internet Gopher and World Wide Web -RRB- changed this model by introducing hypermedia to casual users and by making it easy to use the Internet as a publishing tool . The Gopher system can be thought of as a hypermedia menuing system where items in Gopher menus are links to objects distributed across servers on the Internet -LSB- 8 -RSB- . WWW popularized a form of hypermedia in which documents contain links to other documents residing on distributed servers -LSB- 9 -RSB- . Other forms of hypermedia , such as 3D virtual reality with embedded links to Internet resources are being developed -LSB- 10 -RSB- . So given these developments , video-based hypermedia is a natural development . With NHQT , we want to both develop a new form of hypermedia -LRB- video-based hypermedia -RRB- and at the same time take advantage of existing Internet resources by supporting access to WWW and Gopher sites . To resolve hypermedia links to Internet resources , NHQT requires the presence of separate Internet browser applications which can be handed a `` get this URL '' message . NHQT uses Macintosh AppleEvents as a signalling mechanism to ask the appropriate application to resolve a given URL . Since most popular Macintosh Internet applications such as MacWeb , Netscape , TurboGopher , etc. support the GetURL AppleEvent , we can take advantage of existing network tools , and as easily support new services without having to write a monolithic application that supports all Internet services . 2.3 ATM on Macintosh We envision that the infrastructure of the Internet will be gradually upgraded to incorporate more high speed networks in twenty-first century in order to handle large number of users and the applications which require high aggregate bandwidth . Since ATM technology is maturing -LSB- 11 -RSB- , it is a good candidate for part of the future Internet infrastructure . Under an NSF research grant , we are developing an extensive ATM campus-wide network including high-end workstations and PCs . A small-scale ATM testbed within the campus-wide ATM network for the development of NHQT has a Fore System ASX - 200BXE ATM switch connecting a heterogeneous workstation environment with one Power Macintosh 8100/100AV , one Power Macintosh 9500/120 , one Sun SparcStation 10 , and one SGI high-end Challenge machine . The Macintosh 's support for ATM is implemented within Apple 's Open Transport architecture . Open Transport provides a set of low-overhead Application Programming Interface -LRB- API -RRB- which conforms with X/Open Transport Interface -LRB- XTI -RRB- defined by a consortium of UNIX vendors . Applications written on top of Open Transport enjoy a consistent API which is transport-independent and interoperable with XTI-compliant systems such as various UNIX implementations . Inside of Open Transport , each system component is implemented as a STREAMS-based module -LSB- 12 -RSB- . In order to support various communication protocol stacks such as TCP/IP and AppleTalk and also take advantages of ATM , the ATM Middleware is defined for Macintosh 's ATM environment . The ATM Middleware supports PVC setup , SVC setup via ATM signaling , classical IP over ATM , and raw ATM modules . The design of ATM Middleware essentially shields away any protocols which implement Data-Link Provider Interface -LRB- DLPI -RRB- and the underlying ATM driver . It also simplifies the ATM driver implementation by getting rid of the concern of a single monolithic driver to implement everything for ATM . 3 System Design We recently developed Hyper QuickTime -LRB- HQT -RRB- to validate the concept of video-based hypermedia and then extended this system to develop Networked Hyper QuickTime -LRB- NHQT -RRB- as a prototype system for education-on-demand . HQT transforms a linear video lecture to hypermedia by embedding links to other documents or videos into pertinent section of the video presentation . Annotations and cross references are embedded in the video as URLs pointing to Gopher directories , WWW pages , or other video segments . However , a drawback to HQT is that it only displays video stored on the user 's local hard disk . Of course , video can be distributed on CD-ROM , or downloaded into from a Gopher or WWW server , but for a long video segment , HQT requires large amounts of disk space and probably untolerable retrieval delays . To address these problems , a novel Network QuickTime subsystem design is integrated into HQT to form NHQT . NQT is an underlying subsystem with dual client-and-server role to support the delivery of continuous media stream . In the following subsections , we first describe the concept and user interaction of a hypermedia lecture in HQT . We will also cover the software module design for the entire NHQT system , including the modules that have been implemented for the client site to support user interactions during the hypermedia lecture . Finally , the NQT subsystem design for NHQT is described in detail . 3.1 Hyper QuickTime HQT is developed based on the concept of hypermedia lecture , which enhances a stored lecture so that the viewing experience is not completely passive ; users are expected to pause the video and follow links embedded in the video stream for more information about topics that interest them . In this section , we discuss the concept of a hypermedia lecture in HQT and the QuickTime movie format tailored down for HQT . A graphical user interface is illustrated to demonstrate the user 's and author 's controls over the video . 3.1.1 Hypermedia Lecture To make distance learning more compelling than simply watching a recorded video requires that the user have some control over the level of detail and topics covered . If the user can control the progress of the video and follow links to other relevant videos and documents , we help to replace an important part of a live lecture : the ability to ask questions . Ideally , following a link should be something like asking a question during a live presentation ; the presentation pauses while the presenter tells you more . Beyond embedded links , a hypermedia lecture should also be searchable based on keywords or the text of the narration so that users can quickly jump to a given section of the video . By adding a URL annotation track and a searchable text narration track , we take advantage of the desktop computer as a playback device , and such video-based hypermedia points toward how distance education and interactive television might evolve . In the next section we look at how we store this extra information . 3.1.2 Movie Format Text1 Text2 Text4 Text3 URL1 URL2 URL3 URL4 Video Audio URLs Text Time Figure 3 : Synchronization of different tracks A hypermedia lecture movie in QuickTime consists of at least four tracks : video , audio and two text tracks . Figure 3 illustrates their synchronization based on the timeline of the video . The video and audio tracks could be encoded from a video tapes or animation created by using multimedia authoring tools . Another two text tracks can be added by our application on-the-fly , so authoring a HQT video is typically a two step process . First the audio and video source is digitized , and then the movie is marked up with hypermedia links and the text narration track . One text track called the TEXT Track which stores indexes , the text of the narration or annotations . It should be clear that the narration text will change as the video progresses . Another text track called the URL Track which stores URLs . These URLs point to other related text , images or movie documents on the Internet to provide students more information about this section of lecture . As with the text narration track , the URL track 's content changes as the movie progresses . 3.1.3 User Interface and Operations Figure 4 : User Interface HQT provides two user interfaces , a viewer -LRB- to browse the video -RRB- , and an authoring tool used to add narrative text and URL tracks . The user interface with authoring capability is illustrated in Figure 4 . There are a video window with a control bar , five control buttons on the right-hand side and two text areas on the bottom . The control bar on the video window is created by QuickTime movie controller component . A square indicator on the control bar indicates the current position of the lecture . The bar provides random positioning by moving the square indicator and also VCR-style functions , such as play , pause , fast-forward and fast-rewind by pushing the small buttons on the bar . The learner can also use this bar to adjust the volume of the audio . About the right-hand side buttons , the first three buttons are for the authoring purpose . When an instructor gets a QuickTime lecture movie which is probably encoded by hardware from a video tape , he pushes the first two buttons Add TEXT Track and Add URL Track to add text tracks into the movie on-the-fly . The boxes on the bottom left and right side of the window show the contents of TEXT Track and URL Track , respectively . To add annotations or URLs , the author can use the movie controller indicator to mark a period of movie -LRB- e.g. the shaded area on the control bar in Figure 4 -RRB- and then can type information into the text boxes . After the Update Track button is pushed , the information is saved into the appropriate track in the video . The playback-only interface hides these three buttons to prevent users changing the track contents . Note that once the narrative text and URL tracks have been added to the video , they will remain synchronized with the video and audio tracks even if all or part of the movie is edited using other QuickTime capable video editors . This means that it is possible to use many commercial editing tools in addition to the HQT authoring tool . The More Detail button invokes the appropriate Internet browser application -LRB- typically TurboGopher , MacWeb , or Netscape -RRB- and passes it the current URL to resolve . The Internet browser then retrieves the item referred to by the URL and displays it . If the Gopher or WWW browser is configured to use HQT to display Quicktime video , a URL pointing to another video segment effectively branches the video display to that segment . The user can use Find ... button to search keywords in the TEXT Track . The lecture will be moved to the point at which the contents of the TEXT Track contain the keywords . 3.2 Software Architecture of Networked Hyper QuickTime The architecture of the software modules and the control paths for NHQT are illustrated in Figure 5 . The module of User Interface and Interactions sends control signals to different software modules according to the user 's interaction . For example , when user clicks on the Add URL Track button , the module of Add Text Tracks calls the functions of QuickTime to add a URL track into the current movie . For a movie on local site , the user can add text tracks , update text tracks , search , and apply some VCR-style functions . A Network QuickTime Client Module is implemented under QuickTime to access data from the local disk , memory or through network . Whenever a user wants to get more information , two scenarios may occur . In the first scenario , the URL is a \ normal '' URL . The URL module will invoke Gopher engine at the client site to retrieve desirable information into the local machine from an ftp , Gopher , or WWW server by using ftp , Gopher , or HTTP protocols . This approach works well when the amount of the information does not occupy too much storage space . The Gopher engine at the client site caches the information to the local disk and the transfer is typically within fairly short period of time . In the second scenario , the URL is an \ NQT '' URL . This is suitable for a large video -LRB- perhaps of a long lecture or music -RRB- to avoid consuming too much local disk space and an excessively long delay to download the entire video before playback . To handle references to NQT objects , the URL Module sends the \ NQT '' URL to NQT client module which establishes a connection with a predetermined NQT server . The display will be controlled by NQT client module which communicates with the NQT server instead of using Gopher or WWW to retrieve the enitre remote file onto the client machine . For video which is played from the server , to service the Find ... and VCR-style functions , the NQT client module sends requests to the lecture server and tells the server which data the application needs . Add Text TracksTracks Update Text Engine Search and Interactions URL Functions VCR-like User Interface Module Module NQT Client API QuickTime Gopher Applications Other Internet or ATM network Gopher , WWW or Server Client Server Network QuickTime API Add TEXT track Update track More detail NQT Movie Data in Local Disk Find ... or Add URL track NQT URL Normal URL Figure 5 : The Architecture of the NHQT Software Modules While single-transaction-per-connection stateless protocols -LRB- such as Gopher or HTTP -RRB- can be used to download entire videos , these protocols are not well suited to supporting user controllable video streams . Further details of NQT module design are described in the next subsection . 3.3 Network QuickTime Subsystem Design The NQT subsystem in NHQT enhances the original HQT capability to handle the continuous media stream . From figure 5 , the NQT subsystem consists of an NQT client module at client site and an NQT server at remote site . The NQT client module deals with data retrieval for different media , such as video , audio or music from local disk or NQT server . NQT does not only support NHQT , but also provide a generic network service for the applications built on top of QuickTime . In the following context , we describe the client-server architecture for the NQT subsystem and the roles of NQT client module and NQT server . Then , the implementation detail of the module at the client site , and the internal mechanism for the client and server are explained . 3.3.1 Architecture of Network QuickTime Subsystem The client-server architecture for the NQT subsystem physically separates the data access from data retrieval . NHQT specifies the stream of data that it would like to access and the NQT client module retrieves the data for NHQT from local disk or network . If the data is stored on a local disk , the NQT client module serves this data to the application . If the data is stored at remote site , the NQT client module acts as a client to fetch data from the remote NQT server which retrieves data from server disk , or recursively relays requests -LRB- or data -RRB- to -LRB- or from -RRB- other servers . Our initial implementation is to realize the NQT client module as a novel data handler component for QuickTime on the Macintosh platform . The NQT client module co-resides with the application , which understands QuickTime movie file format . In addition to the Macintosh NQT client , an NQT server has been implemented on UNIX variants -LRB- SunOS 4.1.3 on Sun SparcStation 10 , AIX 4.1.4 on IBM RS/6000 , and IRIX 5.3 on SGI Challenge -RRB- to respond to data retrieval commands from client . We are in the process of implementing a clientserver entity for the NQT server in a distributed hierarchical server setting . The design entices the administrative boundary where admission , accounting , performance , and security concerns can be further addressed in the service contract . Both the application and data allocation can be optimized independently where data access and retrieval are orthogonal to and complement each other . 3.3.2 Network QuickTime Client Module As we mention before , the NQT client module is a new data handler which extends the function of HQT to network access . This module can support the application which is operating on a stream or multiple streams of data for continuous media over QuickTime . To provide a generic interface to the upper layer software , we define a set of extensible Application Programming Interface -LRB- API -RRB- in this module which resembles file system primitives : NQTopen -LRB- -RRB- , NQTclose -LRB- -RRB- , NQTread -LRB- -RRB- , and NQTwrite -LRB- -RRB- . NQ - Topen -LRB- -RRB- -LRB- or NQTclose -LRB- -RRB- -RRB- opens -LRB- or closes -RRB- a data access session upon application 's request . NQTread -LRB- -RRB- -LRB- or NQTwrite -LRB- -RRB- -RRB- reads -LRB- or writes -RRB- a stream of data by specifying the position and amount of data . Once the application opens a data access for a media , the NQT client module associates the source for a stream of data with this session . If the source is local to the application , the data retrieval is through standard memory or file system primitives . If the source is remote , NQT client module establishes network connections with remote servers . The physical network can be any type of supported network medium such as Ethernet or ATM on the Machintosh . The network protocol can be any supported network protocol which provides traditional datagram services such as TCP/IP , or other low latency protocols to support efficient transport of continuous media such as ATM AAL5 . Since the NQT client module does not know the media format , the data transmitted through the network can be a stream of commands , or a stream of media data . 3.3.3 Mechanism of Client and Server When the NQT server receives commands from client -LRB- an application , or NQT client module -RRB- , it requires a file reference from the application . The reference enables the NQT client module to locate the storage for the data and caching & prefetching strategies . The application using NQT subsystem issues standard data handler commands to the NQT client module , and in turn , NQT client module executes the client commands using the aforementioned API . The implementation for NQT client module on Macintosh platform handles two alternative cases . If the file reference refers to a file in local storage , the module binds the commands from client to file system primitives . Otherwise , the module establishes a network connection using Apple 's Open Transport API to the NQT server . NQT subsystem provides two-fold of extensibility from application 's point of view : independence of the other QuickTime components and transparency to access both local and remote data . Since the application translates any user interaction commands such as VCR-style functions or random access into file access patterns , and pass the file access patterns as commands to NQT subsystem , the NQT subsystem is essentially providing an abstraction of virtual file system to the application . 4 Applications NHQT provides a media-rich presentation environment including video , audio , animation , image , and text display . Users have full control of the playback of the video and can repeat sections , search the narrative track for sections containing keywords , and follow hypermedia annotations embedded in the video by the author . Because NHQT is built on top of QuickTime , presentations can consist of video , audio , and MIDI streams , and there are already a variety of authoring and editing tools which support QuickTime . Given these features , NHQT can be applied to a spectrum of different fields . Email Training and Internet Introduction . The Distributed Computing Services -LRB- DCS -RRB- of University of Minnesota provides hundreds of classes to train the faculty , staff , and students how to use the campus computer software and facilities . This training consumes significant amounts of resources , and course scheduling is difficult . As a pilot project , DCS has developed a video training presentation to introduce the basics of Internet , e.g. , telnet , ftp , email , Gopher and WWW . The hypermedia capabilities of NHQT are used to point to the Internet WWW and Gopher severs containing items of interest such as computer sales information , computer lab hours , documentation , and free software . Language Education . This tool has obvious applications for language education . Students can repeat any part of the lecture easily which is useful for reviewing sections which they find difficult . At the same time , the TEXT Track can act as a subtitle or caption so that students can see as well as hear what the instructor is saying . Since a QuickTime movie can embed multiple audio tracks associated with different languages , a lecture can be translated in several languages and saved into several audio tracks . Most importantly , the URL Track can be used to point to either further drills for the concepts or a quiz to test the student 's knowledge of the concepts covered in a given section of the video . Medical Education . The current medical technology produces a lot of diagnostic images and video by x-rays , magnetic resonance imaging -LRB- MRI -RRB- , nuclear medicine -LRB- NM -RRB- , etc. . This data is an important reference and diagnostic tool for physicians . A medical video could present different views of a 3-D human brain or the movements of a patient 's heart . Students in medical school need practice to distinguish between normal and abnormal situations from the video playback or the images . The video or sequence of the images can be encoded in QuickTime movie format for NHQT and used for educational purpose . Experienced physicians can embed annotation in TEXT Track to describe what kind of problem the current playback indicates , e.g , there is a tumor here or the pace maker does not work normally and provide links to more in-depth descriptions and related information for students to explore . Figure 6 is a screen capture of an NMR -LRB- Nuclear Magnetic Resonance -RRB- QuickTime movie . Art Education . A sequence of paintings or pictures can be encoded in QuickTime movie format such that a lecture is like a slide show . The TEXT Track can introduce the artist , title and background of each painting . The instructor can use the audio track for more explanation such as the deep meanings . The URL Track can point to a full screen image if the student wants to look at the high resolution image of a painting and study in detail . Figure 6 : A Human Head NMR QuickTime movie Music Education . Some reference URLs pointing to music clips can be added in the URL Track by an instructor of music department . When the instructor is teaching the history of Baroque music , a student can click on the More Detail button to retrieve a music clip of Bach 's Brandenburg concerto or Haydn 's string quartet as an example . The NQT server sends CD-quality music stream to the client such that the student can listen to high quality music during the lecture . Another possible application would be an analysis of the first movement of Beethoven 's Symphony No. 5 . The instructor can encode this period of music in QuickTime music format and then use authoring functions to add annotations into TEXT Track.The annotations can explain the current music playback , for example , the main theme or the variation of the main theme . Applications beyond Education . While we have concentrated on educational applications of this technology , we can also easily envision commercial applications . There is every reason to expect that if video-based hypermedia becomes popular , some of the links will point to advertisements or commercial services . It is also reasonable to expect that popular hypermedia videos will sell space in their annotations to the highest bidder , just as popular WWW sites today charge others for incorporating links into their pages . This sort of ad-supported media may well help make the technology and content more widely available -LRB- as was the case with broadcast television -RRB- . This will also probably make it easier to find out what sort of shampoo , laundry detergent , and cat food is recommended by the person you are watching in a hypermedia video , and this may well be the price we pay for free access to video-based hypermedia . 5 Conclusion and Future Work The NHQT design illustrates some desirable features of the future distance education applications on the Internet . NHQT provides a video-based hypermedia presentation environment which compliments traditional menu and document based media found in WWW and Gopher . To provide flexible navigation and viewing controls for video presentations , users have content-based search , VCR-style playback controls , and automatic resolution of embedded URL references to Internet information services . This new paradigm shows how delivery of distance education can extend current Internet services and how education-on-demand will help shape Internet 2001 . The NQT subsystem also illustrates the feasibility of networked video or media stream delivery on the current Internet and the future high speed network infrastructure . The NHQT project is in the process for further enhancement . Current NHQT allows only the instructor to add or change the annotations . A cooperative environment can be envisioned ; this environment would allow learners to put their private , group or public annotations into the lecture . Authentication is another important issue to address , since this enables charging for access to materials . Incorporating with learners ' text , audio , or video feedback can make NHQT more interactive for learners and instructors . The feedback may be the questions for the instructor , or the answers for the quizzes or exams . Assuming that video-based media becomes popular , a catalog or directory system should also be provided to display the lecture list . To build up an NQT lecture server to support hundreds or thousands of learners with great amount of user interaction is another challenging issue . File allocation for different media in the storage system of the NQT server is to be studied . ACKNOWLEDGEMENT The authors wish to express their sincere gratitude to Alagu Periyannan , David Singer , and Mengjou Lin in Communications Products and Technologies Group , Apple Computer for providing ATM Middleware and loaning ATM Interface card on Macintosh platform ; to Thilaka S. Sumanaweera , and Yi-Fen Yen in Lucas MRS Imaging Center at Stanford University , who create and provide access to the human head NMR movie clip in QuickTime ; and to Thomas Erickson of Apple Computer for user interface advice . Special thanks also extend to Jenwei Hsieh in Distributed Multimedia Research Center at University of Minnesota for his valuable comments . References -LSB- 1 -RSB- J. Schnepf , V. Mashayekhi , J. Riedle , and D. Du . `` Closing the Gap in Distance Learning : Computer-supported , Participate , Media-Rich Education '' . Educational Technoloy Review , No. 3 , Autumn/Winter , 1994 , pp. 19-25 . -LSB- 2 -RSB- B. Ibrahim , and S.D. Franklin . `` Advanced Educational Uses of the World-Wide Web '' . Computer Networks and ISDN Systems , 1995 , pp . 871-877 . -LSB- 3 -RSB- J.K. Campbell , S. Hurley , S.B. Jones , and N.M. Stephens . `` Contructing Educational Courseware Using NCSA Mosaic and The World-Wide Web '' . Computer Networks and ISDN Systems , 1995 , pp . 887-896 . -LSB- 4 -RSB- P. Juell , D. Brekke , R. Vetter , and J. Wasson `` The Design of a Remote , Low-Cost , Multmedia Classroom '' . Proceedings of the 27th Samll College Computing Symposium , Apr. 1994 , pp. 29-30 . -LSB- 5 -RSB- Dan Dwyer , Kathy Barbieri , and Hellen M. Doerr . `` Creating a Virtual Classroom for Interactive Education on the Web '' . Third International World-Wide Web Conference , Apr. 1995 . -LSB- 6 -RSB- James Schnepf , David H.C. Du , E. Russell Ritenour , and Aaron J. Fahrmann . `` Building Future Medical education Environments Over ATM Networks '' . Communications of the ACM , Vol . 38 , No. 2 , Feb. 1995 , pp . 54-69 . -LSB- 7 -RSB- Apple Computer , Inc. `` INSIDE MACINTOSH : QuickTime '' . Addison Wesley , 1993 . -LSB- 8 -RSB- B. Alberti , F. Anklesaria , P. Lindner , M. McCahill , D. Torrey . `` The Internet Gopher Protocol : a distributed document search and retrieval protocol '' . University of Minnesota . anonymous ftp from boombox.micro.umn.edu , ftp : / / boombox.micro.umn.edu/pub/gopher/gopher protocol / -LSB- 9 -RSB- T. Berners-Lee , R. Cailliau , J. Groff , B. Pollermann `` World Wide Web : the information universe '' . Electronic Networking : Research , Applications and Policy , 1992 . -LSB- 10 -RSB- M. McCahill , T. Erickson . `` Design for a 3D Spatial User Interface for Internet Gopher '' . Ed-Media '95 conference proceedings , 1995 . -LSB- 11 -RSB- Ron Vetter . `` ATM Concepts , Artectures , and Protocols '' . Communications of the ACM , Feb. 1995 . -LSB- 12 -RSB- Apple Computer , Inc. `` INSIDE MACINTOSH : Open Transport '' . Addison Wesley , 1995 .

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O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O B O O O O O O O O O O B B O O O O O O B O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O 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O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O B O O O O B O O O O O O O O O O O B O O O O O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O O B O O O O B O O O O O O O O O B O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O B O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O B I O O O B O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O B O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B I O O O B O O O O O O O B O O O O O O O O O O O B O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B B O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O

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