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Networks & Multimedia

Networks & Multimedia. Amit Pande, Post-doctoral fellow, Department of Computer Science, University of California Davis www.cs.ucdavis.edu/~amit. Material adapted from Internet sources, CS529 course at WPI. Presentation Outline.

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Networks & Multimedia

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  1. Networks & Multimedia Amit Pande, Post-doctoral fellow, Department of Computer Science, University of California Davis www.cs.ucdavis.edu/~amit

  2. Material adapted from Internet sources, CS529 course at WPI

  3. Presentation Outline • Evolution of wireless and Cellular Networks, mobile phones, evolution of Multimedia coding • Multimedia services over Internet

  4. Going back – 15 years • Landline phones • Analog camcorders • CRT TV

  5. Network – the backbone infrastructure

  6. The traditional sense of watching TV channels or playing a video CD are soon disappearing. • GoogleTV has integrated www and search tools to HDTV • Pico-projectors can project HD video from mobile devices

  7. Frequency Transform • Motion compensa-tion • Entropy coding

  8. Frequency Transform • Motion compensa-tion • Entropy coding 50 Kbps 50 Mbps

  9. Network Traffic Today • Internet dominated by text-based applications • Email, FTP, Web Browsing • Very sensitive to loss • Example: lose a byte in abcd.exe program and it crashes! • Not very sensitive to delay • 10’s of seconds ok for Web page download • Minutes for file transfer • Hours for email to delivery

  10. Multimedia on the Internet • Multimedia not as sensitive to loss • Words from speech lost still ok • Frames in video missing still ok • Multimedia can be very sensitive to delay • Interactive session needs one-way delays less than ½ second! • New phenomenon is effects of variation in delay, called jitter!

  11. Jitter-Free Jitter

  12. Video Coding • MPEG -1 352x240 at 30 frames per second (fps) • MPEG -2 1280x720 at 60 fps. CD quality • MPEG -4 objects, low bit-rates

  13. H264 SVC • Parts of the video bit stream can be removed so that the remaining substream can still be decoded • Single-layer vs. Base layer + Enhancement layers Benefits in a mobile environment • Heterogeneous clients • Improved error resiliency

  14. Classes of Internet Multimedia Apps • Streaming stored media • Streaming live media • Real-time interactive media

  15. Streaming Stored Media • Stored on server • 1-way communication, unicast • Examples: pre-recorded songs, famous lectures, video-on-demand, YouTube • RealPlayer,Media Player, Quicktime, FLV • Interactivity, includes pause, ff, rewind… • Delays of 1 to 10 seconds or so tolerable • Need reliable estimate of bandwidth • Not very sensitive to jitter

  16. Streaming Live Media • “Captured” from live camera, radio, T.V. • 1-way communication, maybe multicast • Examples: concerts, radio broadcasts, lectures, IPTV • Can use: RealPlayer,Media Player… but often custom • Limited interactivity… • Limited opportunities for compression, scaling • Delays of 1 to 10 seconds or so tolerable • Need reliable estimate of bandwidth • Not so sensitive to jitter

  17. Streaming Interactive Media • “Captured” from live camera, microphone • 2-way communication • Examples: VoIP, video conference • Very sensitive to delay < 150 ms one-way delay good < 400 ms ok > 400 ms crappy • Sensitive to jitter

  18. TCP or UDP? • Above IP we have UDP and TCP as the de-facto transport protocols. Which to use?

  19. TCP or UDP? • TCP + In order, reliable (no need to control loss) - Congestion control (hard to pick encoding level right) • UDP - Unreliable (need to control loss) + Bandwidth control (easier to control sending rate)

  20. Thank you Questions? Feedback/Comments: amit@cs.ucdavis.edu

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