videoconference introduction

Videoconference Videoconference

erik.luyten@avnet.kuleuven.beAVNet K.U.Leuven

VideoconferenceVideoconference

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What is it?

Real-time (latency < 1second)

Two-way communication

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Sound: echo-cancellation

echo-cancellation

≈ 0,5 sec

≈ 0,5 sec

Near End Far End

echo

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Image: eye contact !

cameralecturer

imagefar-end, (computer)

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Audio signal

Sampling Rate: 44,1 kHzBit Depth: 16 bitStereo: x 2

16 bit x 2 x 44.100 = 1.411.200 bps1,4 Mbit/sec

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Video signal (RGB)

768 pixels

576

pix

els

25 frames/secondEach pixel has 3 values: (3 bytes)

• 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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Ethernet 100 Mbit/sec (shared) LANcompression = 1/2.5

Ethernet 10 Mbit/sec (shared !) LANcompression = 1/25

ISDN line ( 2B + D) : 128Kbit/sec compression = 1/2000

Modem connection : 56 Kbit/sec compression = 1/4600

Video on the network ?

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Network systems

circuit switched network packet switched network

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The network

ISDNH320 protocol128 kbps (2 lines) – 384 kbps (6 lines)

Bandwidth (quality is guaranteed)

IPH323 protocolUp to 4 MbpsCaution: Firewall!Normal connection speeds 384-512 kbps and

higher

Quality depends on available bandwidth

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Videoconference resolution

384x288

CIF

1280x720

HD

768 kbps – 4 Mbps

h.264 (AVC)

h.261, h.263, h264

PAL camera

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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 duplexFull 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 suppressionEcho 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 MixerThe 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 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,...(people wearing glasses!)

Document camera should have “quality light”.

There is a difference between “illumination” and “scene lighting”

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Desktop systemPolycom PVX software + webcamOnly 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,..)

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Roll About system

IP and ISDN H.239Fast setup in meeting room or

connected to existing setup in lecture theatre.

Technical support (for setup) is needed

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Room systeemIP (and ISDN) People & Content (DuoVideo) H.239Integration 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)

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)

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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

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Multipoint – Tandberg MPS200

Media Processing SystemConnects up to 20 video sites

(and 16 audio sites)Gateway between ISDN en IP sitesContinuous presence possibilityh.239 support

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MCU = MPS200

ISDNIP Mixed ISDN/IP

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Continuous Presence

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H.239

PolycomPeople & Content

TandbergDuoVideo

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. (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.

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VC at K.U.LeuvenPentalfa (Gasthuisberg): 90 seatsAuditorium MonetAuditorium WeberAuditorium de MolenAVNet Interaction room: 80 seatsAVNet Greenroom : 5 seatsAVNet mobile setupMediacentrum, ICRI, Astronomy, Computer

Science.…?

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)

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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 year70 multipoint

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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