Audio And Video Over Internet


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Introducing Transmission of Audio and Video through Internet Media.

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Audio And Video Over Internet

  1. 1. Audio and Video over Internet Sudarsun S., M.Tech Checktronix India Pvt Ltd Chennai 600034 [email_address]
  2. 2. Introduction <ul><li>What is Audio/Video over Internet? </li></ul><ul><li>What are the benefits of AV on Internet? </li></ul><ul><ul><li>Cost of traditional communication </li></ul></ul><ul><ul><li>Availability/Mobility with Wireless </li></ul></ul><ul><ul><li>Entertainment Industry </li></ul></ul><ul><ul><ul><li>On demand Movie, Songs </li></ul></ul></ul><ul><ul><ul><li>Duplication Protection </li></ul></ul></ul><ul><ul><li>Distance does not matter! </li></ul></ul><ul><ul><li>Decentralization </li></ul></ul><ul><li>What is and Why Streaming data? </li></ul><ul><li>Real-time Communication Protocols </li></ul>
  3. 3. Agenda <ul><li>Learn the fundamentals of streaming </li></ul><ul><ul><li>TCP, UDP and their limitations </li></ul></ul><ul><ul><li>RTP, RTSP to overcome TCP limitations </li></ul></ul><ul><ul><li>Error Correction and Detection </li></ul></ul><ul><ul><ul><li>Low Quality Piggybacking </li></ul></ul></ul><ul><ul><ul><li>Interleaving </li></ul></ul></ul><ul><li>Understand “On demand” multimedia data </li></ul><ul><ul><li>On demand cinema </li></ul></ul><ul><li>Video conferencing </li></ul>
  4. 4. Overview <ul><li>The big picture </li></ul>
  5. 5. Media Data types <ul><li>Audio : WAV, MP3, RM </li></ul><ul><li>Video: AVI, MPG, MOV, RM </li></ul><ul><li>Bandwidth calculation </li></ul><ul><li>3GPP, 3GPP2 </li></ul><ul><ul><li>3rd generation, high-speed wireless networks </li></ul></ul><ul><li>MPEG4 </li></ul><ul><ul><li>Professional-quality audio and video streams </li></ul></ul><ul><li>H264 formats </li></ul><ul><ul><li>MPEG-4 standard (Part 10) used across 3G for mobile devices to iChat AV for video conferencing to HD for broadcast and DVD </li></ul></ul>
  6. 6. TCP & UDP <ul><li>Connection Oriented – Is that a Overhead ? </li></ul><ul><li>Connectionless – Will that guarantee timely delivery? </li></ul><ul><li>Maximum Effort Reliability vs Just In Time with permissible error rate </li></ul><ul><li>Packet Sequence – Is that an Advantage ? </li></ul><ul><li>Summary of general deficiencies </li></ul>
  7. 7. RTP (RFC 3550) <ul><li>Real-time Transport Protocol on UDP </li></ul><ul><li>Uses RTCP (special set of messages) to exchange periodic reports </li></ul><ul><li>One RTP session per media flow </li></ul><ul><li>16 bit sequence numbers to detect packet loss </li></ul><ul><li>32 bit time stamp to handle jitter due to network </li></ul>
  8. 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. 9. How RTP Works? IP UDP RTP HDR Audio Payload IP UDP RTP HDR Video Payload <ul><li>Uses separate sessions for audio and video </li></ul><ul><li>Uses sequence number to synchronize audio/video </li></ul>
  10. 10. RTP Vs OSI Data Link Frame Relay Ethernet Network IP IP UDP UDP Transport RTP RTP Application MPEG2 video PCMA audio
  11. 11. RTCP <ul><li>Supervise QoS </li></ul><ul><li>Reception reports, Sender reports, Source description </li></ul><ul><li>Reports: packets sent/lost, inter-arrival jitter </li></ul><ul><li>Helps modify sender transmission rate and for diagnostics purpose </li></ul><ul><li>RTCP bandwidth = 5% of session BW </li></ul><ul><li>Commands: SR, RR, SrcDESc, BYE, APP </li></ul>
  12. 12. Continuous Media <ul><li>Real-time (Video Conferences) </li></ul><ul><ul><li>Interactive </li></ul></ul><ul><ul><li>Tight timing relationship </li></ul></ul><ul><ul><li>Error rate/Jitter to be near Zero </li></ul></ul><ul><li>Streaming </li></ul><ul><ul><li>Playback stored media </li></ul></ul><ul><ul><li>Error rate need not be very low </li></ul></ul><ul><ul><li>Loose timing relationship </li></ul></ul>
  13. 13. RTSP (RFC 2326) <ul><li>Application-level protocol for control over the delivery of data with real-time properties. </li></ul><ul><li>Works on top of HTTP </li></ul><ul><li>Extensible framework to enable controlled, on-demand delivery of real-time data. </li></ul><ul><li>Supports live data feeds and stored clips </li></ul><ul><li>Controls multiple data delivery sessions (UDP, multicast UDP, TCP). </li></ul><ul><li>Delivery mechanisms based on RTP. </li></ul>
  14. 15. RTSP Methods <ul><li>OPTIONS- obtain available methods </li></ul><ul><li>SETUP- Establish transport </li></ul><ul><li>ANNOUNCE- alter description of media object. </li></ul><ul><li>DESCRIBE- get low level description of media object. </li></ul><ul><li>PLAY- start playback. </li></ul><ul><li>RECORD- Start recording </li></ul><ul><li>PAUSE- suspend delivery, keep state </li></ul><ul><li>SET_PARAMETER- device or encoding control </li></ul><ul><li>TEARDOWN- remove state. </li></ul>
  15. 16. Error Correction <ul><li>Piggy backing (FEC) </li></ul><ul><li>Interleaving </li></ul><ul><li>Combine both </li></ul>
  16. 17. Low Quality Piggybacking Works for single packet loss, How about multi-packet loss ?
  17. 18. Interleaving Data blackout is recovered with intermittent jitter
  18. 19. Network Strategies <ul><li>Multicasting reduces amount of redundant data transferred </li></ul><ul><li>Streaming media delivery networks allow for multiple, geographically scattered servers (achieved either by splitting or caching ) </li></ul><ul><li>Dedicated networks guarantee bandwidth </li></ul><ul><li>Multiple-access transmissions over Internet—requested info sent from several different locations simultaneously </li></ul>
  19. 20. Streaming Media <ul><li>Three modes in which video information can be streamed: </li></ul><ul><ul><li>Live broadcasting </li></ul></ul><ul><ul><li>On-demand streaming </li></ul></ul><ul><ul><li>Conferencing </li></ul></ul>
  20. 21. Live Broadcasting System SLTA: Simulated Live Transfer Agent (Rebroadcasting)
  21. 22. On-demand System Structure
  22. 23. Streaming Media – On demand <ul><li>Distribution system similar to live broadcasting system, except: </li></ul><ul><ul><li>No direct connection between encoder and server </li></ul></ul><ul><ul><li>Remote proxy servers can cache popular files </li></ul></ul><ul><ul><li>Clients allowed to rewind, fast forward, etc. </li></ul></ul><ul><ul><li>Server proxy transfers only initiated by client </li></ul></ul>
  23. 24. Where to Get More Information <ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul>
  24. 25. Limitations <ul><li>Bandwidth limitation </li></ul><ul><li>Congestion and Quality of network </li></ul><ul><li>Buffer Overhead in Portable devices </li></ul><ul><li>Compression and Decompression overhead </li></ul><ul><li>Security issues </li></ul><ul><ul><li>Eavesdropping </li></ul></ul><ul><ul><li>Duplication by Data Augmentation </li></ul></ul>
  25. 26. Some Servers <ul><li>Audio </li></ul><ul><ul><li>Winamp’s Shoutcast Server </li></ul></ul><ul><ul><li>Streamsicle Broadcast server </li></ul></ul><ul><ul><li>RealMedia Stream server </li></ul></ul><ul><li>Video </li></ul><ul><ul><li>Quicktime Server </li></ul></ul><ul><ul><li>Helix universal server </li></ul></ul><ul><ul><li>Macromedia communication server </li></ul></ul><ul><ul><li>Ffmpeg ( http:// sourceforge .net/projects/ ffmpeg / ) </li></ul></ul>
  26. 27. Conclusion <ul><li>Streaming multimedia poses many challenges to video encoders </li></ul><ul><ul><li>Variability of channel performance </li></ul></ul><ul><ul><li>High server workloads </li></ul></ul><ul><li>Need to adapt coded bit rate to match channel capacities; must be done efficiently and on the fly </li></ul>
  27. 28. Thank You Sudarsun S., M.Tech Director – Research and Development Checktronix India Pvt Ltd [email_address] November 2005