Upload
kuleuven-avnet
View
2.127
Download
1
Tags:
Embed Size (px)
DESCRIPTION
An introduction for videoconference setup in educational environments
Citation preview
2videoconference introduction04/12/2023
What is it?
Real-time (latency < 1second)
Two-way communication
3videoconference introduction04/12/2023
Sound: echo-cancellation
echo-cancellation
≈ 0,5 sec
≈ 0,5 sec
Near End Far End
echo
4videoconference introduction04/12/2023
Image: eye contact !
cameralecturer
imagefar-end, (computer)
5videoconference introduction04/12/2023
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
6videoconference introduction04/12/2023
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
7videoconference introduction04/12/2023
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 ?
8videoconference introduction04/12/2023
Network systems
circuit switched network packet switched network
9videoconference introduction04/12/2023
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
10videoconference introduction04/12/2023
Videoconference resolution
384x288
CIF
1280x720
HD
768 kbps – 4 Mbps
h.264 (AVC)
h.261, h.263, h264
PAL camera
11videoconference introduction04/12/2023
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)
12videoconference introduction04/12/2023
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
13videoconference introduction04/12/2023
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.
14videoconference introduction04/12/2023
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.
15videoconference introduction04/12/2023
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, …
16videoconference introduction04/12/2023
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 !
17videoconference introduction04/12/2023
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”
18videoconference introduction04/12/2023
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,..)
19videoconference introduction04/12/2023
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
20videoconference introduction04/12/2023
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)
21videoconference introduction04/12/2023
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
22videoconference introduction04/12/2023
23videoconference introduction04/12/2023
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
24videoconference introduction04/12/2023
MCU = MPS200
ISDNIP Mixed ISDN/IP
25videoconference introduction04/12/2023
Continuous Presence
26videoconference introduction04/12/2023
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,….)
27videoconference introduction04/12/2023
H-239
IP or ISDN
28videoconference introduction04/12/2023
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.
29videoconference introduction04/12/2023
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)
30videoconference introduction04/12/2023
31videoconference introduction04/12/2023
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)
32videoconference introduction04/12/2023
250 videoconferences each year70 multipoint
33videoconference introduction04/12/2023
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