Network-Enabled Digital Video Recorder (NED) LANMAN’01, March 2001 C. Cranor *, C Kalmanek *, D. Shur *, S. Sibal *, C. Sreenan +, J. van der Merwe * * AT&T Labs – Research, USA + University College Cork, Ireland Contact Author:

NED Motivation Integrate premises storage with Video-on-Demand architecture –Relax access bandwidth requirements Generalize Digital/Personal Video Recorder service –Access to more (shared) content Leverage more efficient off-line encoding

Hard Drive TV Analog Video Tuner Analog Sources: Cable Broadcast Satellite Digital Video Recorder Model for Consumer TV (~20-80 hours) Modem Program-guide Server Users can view “time-shifted” TV content Content may be first acquired and then viewed later. Decoder Encoder

C C C Data Network S VOD Server Clients Streaming versus Downloading Clients request object from server Server streams content to requesting client Sending rate typically same as content encoding rate Client renders content soon after initial content is received (after a “playout” delay of several secs) In downloading, client waits until entire object received Progressive download: Render partial content while continuing to download Request Content

When (not) to Stream Dial-Up DSL Cable Encoding Rate

Encoding Rate

L P C L L L P C C C Backbone Network Access Network P Live Source Portal Client PRISM Architecture Live and On Demand Streaming (up to TV quality) over IP-based Access networks Portals store content, share knowledge of content Get content by name – Prism finds location Virtual TV provider business (don’t have to be directly connected to customers) TV Provider 1 TV Provider 2 TV Provider 3

Hard Drive TV Analog Video Prism Network Analog Video Sources: Cable and Broadcast and Satellite P P MPEG2 over IP DVR client fetches programs (URLs) from Prism portals, and stores them locally, driven by Schedule. NED Client for Prism P L L Decoder Prism Client

Sample User Interface

Implementation Alternatives Reliable client –RTSP: TCP connection for data transfer RTP/RTCP based retransmissions (YPM draft) –Embedded HTTP client –Local Lightweight Portal Not used to share content, only to fetch and store it Leverages portal codebase.

Status of NED Platform selected: –Single board Pentium computer with Linux –Low cost MPEG2 decoder card –Apache web server Next Steps: –Detailed Architectural Design –Implementation

Conclusions NED concept defined Performance trade-offs identified Implementation planned Acknowledgments AT&T Colleagues A. Zelezniak L. Ruedisueli G. Murakami