Videoconference introduction


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An introduction for videoconference setup in educational environments

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Videoconference introduction

  1. 1. Videoconference Videoconference Videoconference Videoconference AVNet K.U.Leuven
  2. 2. What is it? Two-way communication Real-time (latency < 1second) 6/18/2009 videoconference introduction 2
  3. 3. Sound: echo-cancellation echo- cancellation ≈ 0,5 sec echo ≈ 0,5 sec Near End Far End 6/18/2009 videoconference introduction 3
  4. 4. Image: eye contact ! camera image lecturer far-end, (computer) 6/18/2009 videoconference introduction 4
  5. 5. Audio signal Sampling Rate: 44,1 kHz Bit Depth: 16 bit Stereo: x 2 16 bit x 2 x 44.100 = 1.411.200 bps 1,4 Mbit/sec 6/18/2009 videoconference introduction 5
  6. 6. Video signal (RGB) 768 pixels Each pixel has 3 values: (3 bytes) 25 frames/second • Red dot: 256 steps (1 byte) • Green dot: 256 steps (1 byte) • Blue dot: 256 steps (1 byte) Datarate for the uncompressed video signal: 768 x 576 x 3 x 25 = 32 MByte/sec256 Mbit/sec 6/18/2009 videoconference introduction 6
  7. 7. Video on the network ? Ethernet 100 Mbit/sec (shared) LAN compression = 1/2.5 Ethernet 10 Mbit/sec (shared !) LAN compression = 1/25 ISDN line ( 2B + D) : 128Kbit/sec compression = 1/2000 Modem connection : 56 Kbit/sec compression = 1/4600 6/18/2009 videoconference introduction 7
  8. 8. Network systems circuit switched network packet switched network 6/18/2009 videoconference introduction 8
  9. 9. The network ISDN H320 protocol 128 kbps (2 lines) – 384 kbps (6 lines) Bandwidth (quality is guaranteed) IP H323 protocol Up to 4 Mbps Caution: Firewall! Normal connection speeds 384-512 kbps and higher Quality depends on available bandwidth 6/18/2009 videoconference introduction 9
  10. 10. Videoconference resolution PAL camera 1280x720 HD 768 kbps – 4 Mbps 384x288 h.264 (AVC) CIF h.261, h.263, h264 6/18/2009 videoconference introduction 10
  11. 11. Audio processing • (MP3) (32-320kbit/sec, 16 to 48kHz) • G.711 (64kbit/sec, 8kHz) • G.722 (32-64kbit/sec) • G.722.1 (24-32kbit/sec Polycom Siren) • G.728 (16kbit/sec) • AAC (arbitrary bitrates, 8 to 96 kHz) 6/18/2009 videoconference introduction 11
  12. 12. Video setup Put the main camera for recording the lecturer directly above the monitor showing the far end image. Extra cameras for audience, technical setup, speaker panel,... Document camera to show documents and paperwork to local and remote audience. (slides ?) h.239 for computer presentation and/or document camera Videorecorder/DVD player. Videorecorder(s) to record far and near-end images 6/18/2009 videoconference introduction 12
  13. 13. Audio Presenter microphone should be as close as possible to presenter. Speakers for local sound should only reach audience and should not interfere with presenter microphones. Presenter should be able to hear the sound from the remote site. What about the computer sound ? What about the sound from tape or DVD ? Record the near-end and far-end sound on local tape recorder. 6/18/2009 videoconference introduction 13
  14. 14. Audio for interaction: problems Echo : (between two sites) The far-end microphone captures the near-end lecturer sound through the far-end speaker and sends it back (with delay) to the lecturer. Echo delay is around 1 second. Feedback : (one site amplified) The sound of the lecturer is localy amplified. Sound from speaker and microphone are re-inserted in the circuits. This produces a high pitch sound. Reverberation : (one site with or without amplification) The sound from the lecturer or sound system is reflected on the walls, ceiling or floor and will influence the sound quality. Bad speaker placement will produce the same effect. Background noise : (one site with or without amplification) Sound from air conducts, traffic, computers,… will normally be disregarded by the intelligent human hearing system. Automatic microphone mixers have more difficulty in differentiating between noice and genuine sound. 6/18/2009 videoconference introduction 14
  15. 15. Audio for interaction Full duplex - Half duplex Full duplex: All sites can speak at the same time. It feels as if all speakers are in the same room. No operator or automatic mixer action is necessary. Half duplex: The sound of the remote microphone is muted when the local microphone becomes active through automatic or operator control. Echo cancelling - Echo suppression Echo cancelling: only the echo will be suppressed. All other sounds are still available. Echo suppression: all sound is suppressed to cancel the echo effect. This is an (automatic) duplex system. Automatic Conference Mixer - Automatic Microphone Mixer The automatic microphone mixer activates the different microphones in relation to the received volume. It adds the signals end sends them to the local amplifier. The conference mixer has additional (automatic) processing for background noice, constant gain mode (NOM), echo cancelling, … 6/18/2009 videoconference introduction 15
  16. 16. Audio for interaction: solution Echo cancelation benefits the far-end but allows our side to raise the volume without echo problems. An automatic audio processing unit will be faster than human interaction to interact with changes. (but not always more intelligent) When using an automatic system all manual interference will degrade performance. Let the automatic system do the job ! 6/18/2009 videoconference introduction 16
  17. 17. Light Light for the presenter but not for the projection screens. Enough light to allow pictures from the audience. Allow them to see/take notes,… Beware for reflections from/on computer screens, monitors,...(people wearing glasses!) Document camera should have “quality light”. There is a difference between “illumination” and “scene lighting” 6/18/2009 videoconference introduction 17
  18. 18. Desktop system Polycom PVX software + webcam Only IP Compatible with Netmeeting (whiteboard, application sharing, document sharing) MS Windows + USB connection Usable for very small groups (maximum 2 to 3 participants for each endpoint) No echo-cancellation Xmeeting for Mac OSX videoconference ≠ webconference (Acrobat Connect, Skype,..) 6/18/2009 videoconference introduction 18
  19. 19. Roll About system IP and ISDN H.239 Fast setup in meeting room or connected to existing setup in lecture theatre. Technical support (for setup) is needed 6/18/2009 videoconference introduction 19
  20. 20. Room systeem IP (and ISDN) People & Content (DuoVideo) H.239 Integration in existing or new lecture theatre or room. Attention for illumination, camera positions, microphone placements and sound reinforcement. Easy user interface (Crestron, AMX,…) Integrates video, PC, document camera,.. Fast start up time (no installation needed) 6/18/2009 videoconference introduction 20
  21. 21. room wiring diagram •VC code Polycom HDX- 8002 •room automation (AMX, Extron) •sound processing (Clearone) •standard definition camera's (sony EVI-D70) •document camera (XGA resolution) •desktop computer •laptop connection •remote managment (Tandberg Managment System) 6/18/2009 videoconference introduction 21
  22. 22. TelePresence • far-site people should be same size and position as near-site • fixed camera's without zoom • furniture and lighting should be identical • 3 VC codec's and 6 Mbps per site • where is the content ? • limited number of people • meeting vs lecturing 6/18/2009 videoconference introduction 22
  23. 23. Multipoint – Tandberg MPS200 Media Processing System Connects up to 20 video sites (and 16 audio sites) Gateway between ISDN en IP sites Continuous presence possibility h.239 support 6/18/2009 videoconference introduction 23
  24. 24. MCU = MPS200 IP Mixed ISDN/IP ISDN 6/18/2009 videoconference introduction 24
  25. 25. Continuous Presence 6/18/2009 videoconference introduction 25
  26. 26. H.239 Polycom People & Content Tandberg DuoVideo H.239 Standard for transport of second image information in high (XGA) resolution. (computer, document camera) Can also be used for second video resolution channel (VCR, DVD, document camera,….) 6/18/2009 videoconference introduction 26
  27. 27. H-239 IP or ISDN 6/18/2009 videoconference introduction 27
  28. 28. Recording the VC (or a lecture) • Recording the VC content on server. (5 simultanious) • Realtime Streaming to web browsers.(QT, WMV, Real) • h.239 support. • Replay using VC endpoints. (10 simultanious) • Replay using streaming. (VOD) • Export to other systems. 6/18/2009 videoconference introduction 28
  29. 29. VC at K.U.Leuven Pentalfa (Gasthuisberg): 90 seats Auditorium Monet Auditorium Weber Auditorium de Molen AVNet Interaction room: 80 seats AVNet Greenroom : 5 seats AVNet mobile setup Mediacentrum, ICRI, Astronomy, Computer Science. …? 6/18/2009 videoconference introduction 29
  30. 30. videoconference network setup • dedicated network segment • de-militarised zone • no firewall traversal hard/software needed • no NAT (network address translation) • MCU mulipoint control unit • gatekeeper • TMS (Tandberg Managment System) • codian IPVCR (Tandberg) 6/18/2009 videoconference introduction 30
  31. 31. Projects • Pentalfa (multipoint-Flanders) • Venus (multipoint-Europe) • Industrieel beleid (Leuven, Gent, Kortrijk ) • Notariaat (promotiezaal, Leuven and Kortrijk) • Pedagogie (on location, Leuven and Kortrijk) • Lessen van de 21ste eeuw (multipoint) • Erasmus Mundus Nanotechnology (Leuven, Leiden, Chalmers and Dresden) • Earth Observation (Leuven and Purdue) • International Student Business Game (7 sites, Europe, Association) 6/18/2009 videoconference introduction 31
  32. 32. 250 videoconferences each year 70 multipoint 6/18/2009 videoconference introduction 32
  33. 33. plan your videoconferences • Early resource reservation • A short introduction and competent support can solve problems and anxieties • Provide references for contact • Provide information on website 6/18/2009 videoconference introduction 33
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