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Audio And Video Over Internet

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Introducing Transmission of Audio and Video through Internet Media.

Introducing Transmission of Audio and Video through Internet Media.

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  • 1. Audio and Video over Internet Sudarsun S., M.Tech Checktronix India Pvt Ltd Chennai 600034 [email_address]
  • 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
  • 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
  • 4. Overview
    • The big picture
  • 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
  • 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
  • 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
  • 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 ;
  • 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
  • 10. RTP Vs OSI Data Link Frame Relay Ethernet Network IP IP UDP UDP Transport RTP RTP Application MPEG2 video PCMA audio
  • 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
  • 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
  • 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.
  • 14.  
  • 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.
  • 16. Error Correction
    • Piggy backing (FEC)
    • Interleaving
    • Combine both
  • 17. Low Quality Piggybacking Works for single packet loss, How about multi-packet loss ?
  • 18. Interleaving Data blackout is recovered with intermittent jitter
  • 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
  • 20. Streaming Media
    • Three modes in which video information can be streamed:
      • Live broadcasting
      • On-demand streaming
      • Conferencing
  • 21. Live Broadcasting System SLTA: Simulated Live Transfer Agent (Rebroadcasting)
  • 22. On-demand System Structure
  • 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
  • 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/
  • 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
  • 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 / )
  • 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
  • 28. Thank You Sudarsun S., M.Tech Director – Research and Development Checktronix India Pvt Ltd [email_address] November 2005

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