Sampling Rate: 44,1 kHz
Bit Depth: 16 bit
Stereo: x 2
16 bit x 2 x 44.100 = 1.411.200 bps
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Video signal (RGB)
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
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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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128 kbps (2 lines) – 384 kbps (6 lines)
Bandwidth (quality is guaranteed)
Up to 4 Mbps
Normal connection speeds 384-512 kbps and higher
Quality depends on available bandwidth
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768 kbps – 4 Mbps
384x288 h.264 (AVC)
h.261, h.263, h264
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Put the main camera for recording the lecturer directly
above the monitor showing the far end image.
Extra cameras for audience, technical setup, speaker
Document camera to show documents and paperwork to
local and remote audience. (slides ?)
h.239 for computer presentation and/or document
Videorecorder(s) to record far and near-end images
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Presenter microphone should be as close as possible to
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
What about the computer sound ?
What about the sound from tape or DVD ?
Record the near-end and far-end sound on local tape
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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
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, …
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Audio for interaction: solution
Echo cancelation benefits the far-end but allows
our side to raise the volume without echo
An automatic audio processing unit will be faster
than human interaction to interact with
(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
Light for the presenter but not for the
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”
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Polycom PVX software + webcam
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)
Xmeeting for Mac OSX
videoconference ≠ webconference (Acrobat Connect, Skype,..)
6/18/2009 videoconference introduction 18
Roll About system
IP and ISDN
Fast setup in meeting room or
connected to existing setup in
Technical support (for setup) is needed
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IP (and ISDN)
People & Content (DuoVideo) H.239
Integration in existing or new lecture theatre or
Attention for illumination, camera
positions, microphone placements and sound
Easy user interface
Integrates video, PC,
Fast start up time
(no installation needed)
6/18/2009 videoconference introduction 20
• far-site people should be
same size and position as
• fixed camera's without
• 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
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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
6/18/2009 videoconference introduction 23
People & Content
Standard for transport of second image information in
high (XGA) resolution. (computer, document
Can also be used for second video resolution channel
(VCR, DVD, document camera,….)
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IP or ISDN
6/18/2009 videoconference introduction 27
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
VC at K.U.Leuven
Pentalfa (Gasthuisberg): 90 seats
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
videoconference network setup
• dedicated network segment
• de-militarised zone
• no firewall traversal hard/software needed
• no NAT (network address translation)
• MCU mulipoint control unit
• TMS (Tandberg Managment System)
• codian IPVCR (Tandberg)
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• 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
6/18/2009 videoconference introduction 32
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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