NETWORK-BASED DIGITAL VIDEO LIBRARY SYSTEM

NETWORK-BASED DIGITAL VIDEO LIBRARY SYSTEM

Janusz Gozdecki, Piotr Pacyna, Zdzislaw Papir, Rafal Stankiewicz, Andrzej Szymanski

Department of Telecommunications, University of Mining and Metallurgy al. Mickiewicza 30, 30-059 Kraków, Poland,

e-mail: {gozdecki, pacyna, papir, rstankie, szyman}@kt.agh.edu.pl 1. Introduction

The Digital Video Library System was developed in the Department of Telecom-

munications as a part of the Broadband Trial Integration Project (ACTS AC 362) sponsored by the European Commision. It is a storage and management system for digitally encoded video, capable of synchronous streaming the video content towards the users on request [1].

Unique features of the Digital Video Library System include the ability to process compound queries submitted by users to find a particular film, allow the users to browse the film database, request additional information on a specific topic, and finally submit a request to start video streaming. During the streaming the application allows the user to perform trick-mode functions typical of a VCR [2,6].

There are two interfaces: user interface consisting of four web-based pages facilitating server browsing, and the content manager interface, which consists of five pages to enable efficient management.

The application is able to support several simultaneous point-to-multipoint sessions and to control the QoS, i.e. to maintain appropriate quality of the video during the network transmission. The System uses advanced features of the underlying ATM PON access network like: support for IPv6, support for point-to-multipoint sessions with use of IPv6 multicast, and network resource reservation at the IP layer with RSVP protocol, although its use is not restricted to ATM networks [4].

2. Key features The Digital Video Library System has the following properties [5]: ?? enables video database browsing, ?? facilitates selection of a film with keyword search, ?? provides hypertext descriptions for stored films, ?? supports MPEG1 format for video streaming,

?? supports up to 10 concurrent point-to-multipoint sessions, ?? implements QoS control at the user level, ?? enables film indexing and efficient video content management, ?? implements episodes - fragments of films which behave like separate films, ?? supports URL for each film or episode, thus provides access to a particular film or episode

from any web page,

The Digital Video Library System employs a two-level hierarchical structure consisting of categories (top level) and subcategories (lower level). Each film is assigned to one category and subcategory. Category data together with other catalogue information, like film title, author name and keywords, allow for efficient search over the video library. Additional information, stored in the database contains licence agreement, length of the film, technical data and either textual or hypertextual description. From the engineering point of view the novel features of the application are: ?? support for IPv6, ?? support for multicast, ?? resource reservation at the IPv6 layer. 3. System Architecture

The architecture of The System is shown on fig. 1. The heart of the system is The Oracle Video ServerTM (OVS). Its main role is to store the digital video content and deliver video streams to the clients in real time. The server has built-in QoS mechanisms, which limit the number of simultaneous streaming sessions. Films are stored on the disk array managed exclusively by OVS, thus improving the overall performance.

The RSVP/Proxy modules take an important part in the video retrieval process. The server module captures the unicast IPv4 UDP MPEG stream generated by the OVS and distribute it over the network using IPv6 unicast or multicast session. On the client side, the proxy module receives the stream and sends it to the player using IPv4. The RSVP/Proxy modules also establish RSVP reservations for each of the video sessions, thus applying QoS guarantees at the network level.

The Oracle Video Player (ActiveX control) decodes the video stream and displays it on the user’s screen. It also provides support for playback control (play, stop, pause, rewind, fast forward operations) and for displaying film position (time) and setting the volume.

The Internet Explorer acts as a front-end application. The displayed pages are formatted using HTML layout. Data acquisition (for example query criteria) is done via HTML forms. The Visual Basic scripts handle events on the user’s side and check the correctness of data one enters in the forms. Video content (films) is displayed using Oracle Video Player ActiveX control. Also many ActiveX controls are used to control the play process (START, STOP, rewind buttons) or serve as dynamic objects (scrollbars, counters). The Internet Explorer communicates with Apache WWW server with HTTP protocol over IPv4 or IPv6 without reservation (see Network Aspects).

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HTML Layout and Forms

Fig. 1 System architecture Apache WWW server processes requests from user’s side either by serving static HTML

pages or running CGI scripts written in Perl. Also it is an authorization module for the administrative access. The user authorization is based on standard username-password scheme.

The Perl scripts are the control centre of the system. They perform various tasks, in particular: ?? process requests from client side, ?? generate SQL queries for the database, ?? execute UNIX commands, ?? retrieve and process query results, ?? format the results in HTML.

The information on available video titles, their prose description and technical properties is organised in a SQL database running on a RDBMS platform (Postgres). It includes information that may be interesting to the user and some meta-data that maintains the integrity of the whole server installation.

The following attributes are stored in the database: ?? Technical parameters:

?? MPEG filename, ?? file size, ?? display dimensions, ?? encoding technique (e.g. MPEG 1), ?? encoding bit rate, ?? refresh rate (frames per second), ?? film length, ?? RSVP parameters (network resource specification, T-Spec).

?? Catalogue information of film: ?? film title, ?? author, ?? licensing terms, ?? license expiry, ?? category and subcategory a given film belongs to, ?? keywords, ?? film status (avaliable/unavaliable) ?? a pointer to the description of film (either text or hypertext), ?? episodes information.

4. Network aspects

The application may run either in IPv4 or IPv6 environment. The protocol stack used is shown on fig. 2 [3,5]. Use of the IP protocol makes the application interoperable over various networking technologies (Ethernet, ATM). In order to provide Quality of Service the application may signal the resource requirements to the network. Reservation is done via RSVP. Of course underlying network nodes must be RSVP-aware for the traffic contract to be obeyed. The Video Library System supports both unicast and multicast connections. In latter case one of the clients has full control over the session while others can only join the session, watch the video or leave the session.

The resource reservation applies only to video traffic. The other traffic (HTTP) is always sent without QoS guarantees, and is always unicast.

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Fig. 2 Network layers

The Digital Video Library System was tested in the testbed network shown in fig. 3. The network is a part of the ACTS AC 038 Broad Band Loop project. The access network, shown on the right part of the fig. 3 comprises of a single fibre Passive Optical Network (PON) with a splitting ratio of up to 16. The PON consists of the APON LT (Line Termination), a single fibre ODN (Optical Distribution Network) and up to 16 ONUs (Optical Network Units) per link. Customers are connected directly to the ONUs or use an xDSL modem in the last drop depending on the application. So far in our testbed we use three user’s terminals directly connected to the ONUs. Broadband service interface for the customers is ATM25. ATM25 provides transparent ATM transport service to the customer premises equipment and is recommended by the Full Service Access Network (FSAN) group. The network has two networking layers: the IP layer that is used by the application client to communicate with the application server through the routers, and the ATM layer used by the IP router and terminals to setup connections within the optical part of network.

OLT - Optical Line Termination ADM - Add Drop Multiplexer ONU - Optical Network Unit TPSA - Polish National Telecom UMM - University of Mining and Metallurgy

Fig. 3 Testbed network structure

All main tests were performed in the forementioned network. The Digital Video Library

System was also tested on the 2Mbps link to Denmark (see fig. 3). The access network structure in Denmark was similar to that in fig. 3 but lacked the SDH ring. Also, another tests were performed on Telecom Geneva ’98. The network structure was similar to that on fig. 3 but also lacked the SDH ring.

5. User interface

User interface, referred to as Video Library Client, is a front-end application, which allows users to access the server, search for a particular film or film episode and start streaming the selected film towards the user or a group of users. Video Library Client uses the WWW technology [2], to provide easy and comfortable access to the content of the server and to the companion information such as a hypertext description of films and related information about the author of the film, licensing terms, technical parameters (duration, bitstream, encoding type) and others.

The user interface offers advanced search capabilities to allow definition of subject of interest. The search criteria may include: film title, author, category/subcategory or search by keywords (see fig. 4).

When a user requests to play a film, methods to communicate network requirements are invoked and result in reservation of appropriate resources along the video transmission path in the network.

The user interface differs for ‘active’ and ‘passive’ video clients. The active video client is a person who can communicate with the video server, select video for streaming, and receive it. He decides what video will be sent over the network, and has full control over the video: can start/stop/pause/rewind etc. (see fig. 5).

Fig. 4. User interface – search results page (Active client)

Play button

Go back to the search

page Film title

Episode title

Search summary

Results window

Fig. 5. User interface – play page (Active client) He is also entitled to decide on the resource reservation parameters. Active video client,

when deciding on the video film to watch, initiates the setup of a point-to-multipoint session. At the very beginning he is the only client receiving the video flow destined for the session. Later on, other clients, so called passive clients, may join and thus enlarge the multicast group.

Passive video clients are those, who have limited control over the video. They can get a list of running multicast sessions and join the preferred one. Their functionality is similar to a man watching tv, who can choose a channel out of those currently 'on air' but can not modify the tv programme nor become a broadcaster.

6. Content manager interface The Digital Video Library System provides a separate interface for content management.

It supports activities specific for a content manager including content update, assignment of new titles to a category and subcategory, preparation of detailed descriptions, and making titles available for users (see fig. 6).

Position scrollbar

Volume control

Player window

Info window

Control buttons

Click to play

another film

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page

Fig. 6 Content manager - film properties page It also enables definition of film fragments (episodes) within a film, that can be later

referenced by users. Content Manager Interface, part of the application restricted to Content Manager only, is used to fill the database with content descriptors (content labels). Among the descriptors are the default resource requirements of a video film expressed in network-related terms as well as application-related descriptors (encoding type, video resolution, number of frames per second etc.). The former are used by the application to reserve appropriate resources, while the latter are intended for users to notify them about basic characteristics of the content they demand.

The Administrator Interface allows the system administrator to perform the following actions: ?? adding new video content (registering films in the database), ?? searching and modifying the existing catalogue and technical information, ?? defining and modifying the episodes, ?? adding and modifying list of categories and their subcategories, ?? creating textual descriptons or entering a link to hypertextual description. Only entitled users are allowed to change the content of the library. For security reasons the Administrator Interface is protected with a username and password.

7. Areas of application The Digital Video Library System may be deployed in all areas where the digital video

may ehance the quality of services brought to clients. For travel offices and hotels the opportunity of enriching their standard services with video sequences will attract the customers. Potential clients planning a trip or vacation will have chance to get briefly acquainted with the tourist attractions of countries or cities they are going to visit or

investigate other options proposed by a travel-agent as well as evaluate accomodation facilities in the hotels.

The application also proved to be useful in high schools and universities and in other educational institutions where it was used to extend teaching curricula making them more up-to-date.

Incorporation of video into the product advertisements brings quite new and very advantageous capabilities for companies willing to expand to new markets using new marketing techniques, like multimedia kiosks during expositions and fairs, conferences and workshops.

Modularity of application enables easy adaptation to various uses.

8. Bibliography

1. J. Gozdecki, P. Pacyna, Z. Papir, Video retrieval service over an ATM access network under IPV6/RSVP protocols, accepted to Journal of Applied System Studies, November 1999.

2. M. Leszczuk, P. Pacyna, Z. Papir, Video Content Streaming Service using IP/RSVP Protocol Stack, IEEE Workshop on Internet Applications, WIAPP’99, San Jose (CA), USA, 26-27 July 1999, pp. 89-93.

3. J. Gozdecki, Z. Papir, Transmmision of multimedia services in the Internet using RSVP, The EURASIP Conference DSP for Multimedia Communications and Services, Kraków, 24-26 June 1999, CD-ROM.

4. P. Pacyna, Z. Papir, J. Gozdecki, M. Leszczuk, Video Retrieval Application for Distributed Education – Requirements, Implementation and Results, International Symposium on Intelligent Multimedia and Distance Education - Advances in Intelligent Computation and Multimedia Systems ISIMADE’99, Baden-Baden, 2-7 August 1999, pp. 31-37.

5. P. Pacyna, J. Gozdecki, Z. Papir, R. Stankiewicz, A. Szymanski, Specification and implementation of the server, ACTS AC 362 Broadband Trial Integration Milestone 3.2.3, December 1999, Krakow, Poland

6. E. Bertelsen, P. Pacyna, et al., User Requirements and applications and services specification, ACTS AC 362 Broadband Trial Integration Deliverable 3.1.0, August 1998, Denmark.