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Audio and Video over Internet. Sudarsun S., M.Tech Checktronix India Pvt Ltd Chennai 600034 sudar@burning-glass.com. Introduction. What is Audio/Video over Internet? What are the benefits of AV on Internet? Cost of traditional communication Availability/Mobility with Wireless

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Audio and Video over Internet


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    1. Audio and Video over Internet Sudarsun S., M.Tech Checktronix India Pvt Ltd Chennai 600034 sudar@burning-glass.com Sudarsun S

    2. Introduction • What is Audio/Video over Internet? • What are the benefits of AV on Internet? • Cost of traditional communication • Availability/Mobility with Wireless • Entertainment Industry • On demand Movie, Songs • Duplication Protection • Distance does not matter! • Decentralization • What is and Why Streaming data? • Real-time Communication Protocols Sudarsun S

    3. Agenda • Learn the fundamentals of streaming • TCP, UDP and their limitations • RTP, RTSP to overcome TCP limitations • Error Correction and Detection • Low Quality Piggybacking • Interleaving • Understand “On demand” multimedia data • On demand cinema • Video conferencing Sudarsun S

    4. Overview • The big picture Sudarsun S

    5. Media Data types • Audio : WAV, MP3, RM • Video: AVI, MPG, MOV, RM • Bandwidth calculation • 3GPP, 3GPP2 • 3rd generation, high-speed wireless networks • MPEG4 • Professional-quality audio and video streams • H264 formats • MPEG-4 standard (Part 10) used across 3G for mobile devices to iChat AV for video conferencing to HD for broadcast and DVD Sudarsun S

    6. TCP & UDP • Connection Oriented – Is that a Overhead ? • Connectionless – Will that guarantee timely delivery? • Maximum Effort Reliability vs Just In Time with permissible error rate • Packet Sequence – Is that an Advantage ? • Summary of general deficiencies Sudarsun S

    7. RTP (RFC 3550) • Real-time Transport Protocol on UDP • Uses RTCP (special set of messages) to exchange periodic reports • One RTP session per media flow • 16 bit sequence numbers to detect packet loss • 32 bit time stamp to handle jitter due to network Sudarsun S

    8. RTP Format (V) Version; 2 bits (P) Padding; 1 bit. (X) Extension; 1 bit. (CC) CSRC Count; 4 bits. (M) Marker; 1 bit. (PT) Payload Type; 7 bits. Sequence Number; 16 bits. Time Stamp; 32 bits. SyncSRCId; 32 bits. ContributingSRCId List; Sudarsun S

    9. How RTP Works? IP UDP RTP HDR Audio Payload IP UDP RTP HDR Video Payload • Uses separate sessions for audio and video • Uses sequence number to synchronize audio/video Sudarsun S

    10. RTP Vs OSI Sudarsun S

    11. RTCP • Supervise QoS • Reception reports, Sender reports, Source description • Reports: packets sent/lost, inter-arrival jitter • Helps modify sender transmission rate and for diagnostics purpose • RTCP bandwidth = 5% of session BW • Commands: SR, RR, SrcDESc, BYE, APP Sudarsun S

    12. Continuous Media • Real-time (Video Conferences) • Interactive • Tight timing relationship • Error rate/Jitter to be near Zero • Streaming • Playback stored media • Error rate need not be very low • Loose timing relationship Sudarsun S

    13. RTSP (RFC 2326) • Application-level protocol for control over the delivery of data with real-time properties. • Works on top of HTTP • Extensible framework to enable controlled, on-demand delivery of real-time data. • Supports live data feeds and stored clips • Controls multiple data delivery sessions (UDP, multicast UDP, TCP). • Delivery mechanisms based on RTP. Sudarsun S

    14. Sudarsun S

    15. RTSP Methods • OPTIONS- obtain available methods • SETUP- Establish transport • ANNOUNCE- alter description of media object. • DESCRIBE- get low level description of media object. • PLAY- start playback. • RECORD- Start recording • PAUSE- suspend delivery, keep state • SET_PARAMETER- device or encoding control • TEARDOWN- remove state. Sudarsun S

    16. Error Correction • Piggy backing (FEC) • Interleaving • Combine both Sudarsun S

    17. Low Quality Piggybacking Works for single packet loss, How about multi-packet loss ? Sudarsun S

    18. Interleaving Data blackout is recovered with intermittent jitter Sudarsun S

    19. Network Strategies • Multicasting reduces amount of redundant data transferred • Streaming media delivery networks allow for multiple, geographically scattered servers (achieved either by splitting or caching) • Dedicated networks guarantee bandwidth • Multiple-access transmissions over Internet—requested info sent from several different locations simultaneously Sudarsun S

    20. Streaming Media • Three modes in which video information can be streamed: • Live broadcasting • On-demand streaming • Conferencing Sudarsun S

    21. Live Broadcasting System SLTA: Simulated Live Transfer Agent (Rebroadcasting) Sudarsun S

    22. On-demand System Structure Sudarsun S

    23. Streaming Media – On demand • Distribution system similar to live broadcasting system, except: • No direct connection between encoder and server • Remote proxy servers can cache popular files • Clients allowed to rewind, fast forward, etc. • Server proxy transfers only initiated by client Sudarsun S

    24. Where to Get More Information • http://www.mediacollege.com/video/streaming/overview.html • http://www.apple.com/quicktime/technologies/ • http://www.teamsolutions.co.uk/streaming.html • http://archive.dstc.edu.au/RDU/staff/jane-hunter/video-streaming.html • http://www2.umist.ac.uk/isd/lwt/clickgo/the_guide/the_guide.htm • http://emoney.al.ru/capture-streaming-video-and-audio/ • http://www.cit.cornell.edu/atc/itsupport/streaming.shtml • http://www.yolinux.com/TUTORIALS/LinuxTutorialRealVideoStreaming.html • http://nms.csail.mit.edu/projects/oxygentv/ Sudarsun S

    25. Limitations • Bandwidth limitation • Congestion and Quality of network • Buffer Overhead in Portable devices • Compression and Decompression overhead • Security issues • Eavesdropping • Duplication by Data Augmentation Sudarsun S

    26. Some Servers • Audio • Winamp’s Shoutcast Server • Streamsicle Broadcast server • RealMedia Stream server • Video • Quicktime Server • Helix universal server • Macromedia communication server • Ffmpeg (http://sourceforge.net/projects/ffmpeg/) Sudarsun S

    27. Conclusion • Streaming multimedia poses many challenges to video encoders • Variability of channel performance • High server workloads • Need to adapt coded bit rate to match channel capacities; must be done efficiently and on the fly Sudarsun S

    28. Thank You Sudarsun S., M.Tech Director – Research and Development Checktronix India Pvt Ltd sudarsun@burning-glass.com November 2005 Sudarsun S