Shinji Shimojo Japan Computer Center Osaka University 5-1 Mihogaoka, Ibaraki 567 JAPAN Tel: +81 (6) 879-8793 fax: 06-879-8814 shimojo@center.osaka-u.ac.jp ------------ DAVIC Internet Gateway Shinji Shimojo (Computer Center, Osaka University) Masataka Ohta (Tokyo Institute of Technology) Contact Address: Shinji Shimojo 5-1 Mihogaoka, Ibaraki City Computer Center, Osaka University 567 JAPAN TEL: +81-6-879-8793 FAX: +81-6-879-8794 E-mail: shimojo@center.osaka-u.ac.jp * Introduction Digital Audio Video Council (DAVIC: : http://www.davic.org) is a non-profit organization for standardizing digital audio video applications including Video On Demand. DAVIC 1.0, our first specification, is a VOD system which distributes MPEG2 audio/video contents to set top units connected through ATM network. We are developing a system architecture to expand the provision of the audio/video contents through the Internet. That is, MPEG2 contents prepared for DAVIC 1.0 (called DAVIC contents) are provided to computers or terminals connected to the Internet. For the system architecture, we propose a gateway between DAVIC ATM network and the Internet and define its service function. The gateway provides web interface for the terminals to access its contents and retrieve the requested contents from a DAVIC contents server. The primary technical issues for the gateway services include 1) service structure, 2) realtime/semi-realtime provision of MPEG2 contents, and 3) access and control of provided contents. In this short notes, we briefly describe our current proposal for the DAVIC and open issues. * Service Structure Although we assume a uniform network capacity (ATM) and a uniform functionality of terminals in the DAVIC 1.0, we should deal with the diversity of network capacity and functionaries of terminals in the Internet. For dealing the diversity, at least three ways for prividing the contents are considered as follows: A) Batch Internet content provider The gateway provides its contents as a file. Terminals request the contents to the gateway and receive it as a file. B) Semi-realtime (best effort) Internet content provider The server provides its contents as a continuous stream. Terminals request the contents and receive the stream which contains the contents. The stream is transferred as is, through the best effort service. C) Realtime Internet content provider The server provides its contents as a realtime continuous stream. Terminals request the contents and receive the realtime stream which contains the contents. The stream is transferred through the guaranteed service. Resource reservation mechanism in the Internet is assumed. For B) and C), encapsulation of contents through the Internet is defined in the next section. * Realtime/semi-realtime Provision of MPEG2 Contents To achieve realtime/semi-realtime provision of the MPEG2 contents from the gateway, it has two primary functions, absorbing delay jitter and encapsulation of the contents for the Internet terminals. We consider three types of encapsulations according to the services: A) MPEG2-TS or -PS over TCP for batched access, B) MPEG2-TS over RTP (RFC 1889 and 1890) over IP-multicast for best-effort access, and C) MPEG2-TS over RTP over RSVP guaranteed service (encapsulation of MPEG over RTP has been proposed as an internet draft (draft-ietf-avt-mpeg-01.txt)). * Access and Control of Provided Contents. A web forms a user interface through which terminals access Internet contents as well as DAVIC contents. It performs two primary function for Internet terminals, program selection and contents playback control. Since DAVIC adopts DSM-CC for these functions, the gateway translates URL and http access into DSM-CC. Since program selection and playback control is performed through the web interface, URL should contain A) a file name for FTP over TCP for batch access, B) UDP port #, RTP payload type, program name, QoS etc. for realtime/semi-realtime access. For, B) we should expand current URL. For contents play back control, JAVA extension or new URL for DSM-CC could be used, for example, as follows: eg) dsm-cc://hostport/program.play dsm-cc://hostport/program.rewind Also, the method for embedding URLs within a MPEG2 picture should be defined which enables that one can invoke a URL attacked to a MPEG2 picture by clicking it. This functionality gives an equivalent to encode a binary image with attached URL.