Videoconference Videoconference Videoconference Videoconference

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					    Videoconference
    Videoconference

    Videoconference
     Videoconference
erik.luyten@avnet.kuleuven.be
       AVNet K.U.Leuven
                                   What is it?



                                            Two-way communication




          Real-time (latency < 1second)




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                 Sound: echo-cancelation


                                              echo
                                            cancellor
                                ≈ 0,5 sec

                                                        echo


                                ≈ 0,5 sec



          Near End                           Far End

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                    Image: eye contact !
                               camera            image
                               lecturer   far-end, (computer)




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                              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


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                               Video signal (RGB)

                         768 pixels


                                                         
576 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/sec       256 Mbit/sec

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                 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

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                         Network systems




     circuit switched network            packet switched network
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                                   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
               Quality depends on available bandwidth

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              Videoconference resolution




                                           1280x720
                                              HD

                                      757 - 2024 kb/sec

              384x288                      h.264 (AVC)
                CIF

          h.261, h.263, h264




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                         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)



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                               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

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                                         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.



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            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.




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                        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),…




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          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 !


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                                         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,...
   Document camera should have “quality light”.
   There is a difference between “illumination”
     and “scene lighting”


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                          Desktop system
    Polycom PVX software + webcam
    Over 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-cancelation

    Xmeeting for Mac OSX



    videoconference         webconference (Acrobat Connect, Skype,..)


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                     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




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                         Room systeem
  IP en 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)
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                  Multipoint - 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

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                            MCU = MPS200




                               IP    Mixed ISDN/IP   ISDN




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                     Continuous Presence




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                                             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,….)


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                                         H-239




                                   IP or ISDN




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              Recording the VC (or a lecture)

•     Recording the VC content on server.
•     Streaming to web browsers.
•     h.239 support.
•     Replay using VC endpoints.
•     Replay using streaming.
•     Export to other systems using MPEG-1 download.




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                     VC at K.U.Leuven

   Pentalfa (Gasthuisberg): 90 seats
   AVNet Interactieruimte : 80 seats
   AVNet Greenroom : 5 seats
   AVNet mobile setup
   Tavernier Studio : 30 seats
   Mediacentrum, ICRI,
   …?

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                                   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)

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                 250 videoconferences each year
                          70 multipoint




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                         Course of action
• Early resource reservation
• A short introduction and competent
  support can solve problems and anxieties
• Provide references for contact
• Provide information on website




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