What is it?
Real-time (latency < 1second)
Sound: echo-cancelation
echo echo cancellor cancellor ≈ 0,5 sec ≈ 0,5 sec echo echoImage: eye contact !
camera lecturer
image
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
Video signal (RGB)
768 pixels 768 pixels 576 pixels 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:
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
Network systems
The network
ISDN
ISDN
H320 protocol H320 protocol 128 kbps128 kbps (2 lines)(2 lines) –– 384 kbps 384 kbps (6 lines)(6 lines) Bandwidth (quality is guaranteed
Bandwidth (quality is guaranteed
)
)
IP
IP
H323 protocol H323 protocol Up to 4 Mbps Up to 4 Mbps Caution: Firewall! Caution: Firewall!Normal connection speeds 384-512 kbps
Normal connection speeds 384-512 kbps
Quality depends on available bandwidth
Videoconference resolution
384x288 CIF 1280x720 HD 757 - 2024 kb/sec h.264 (AVC) h.261, h.263, h264Audio 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)
Video setup
Put the
Put the main main camera camera for recording for recording the the lecturer directlylecturer directly above
above the monitor the monitor showing showing the the far far end image.end image. Extra
Extra cameras for audiencecameras for audience, , technical setuptechnical setup, speaker, speaker panel,...
panel,...
Document camera
Document camera to to show show documents documents and and paperwork topaperwork to local
local and and remote audienceremote audience. (. (slides slides ?)?) h.239
h.239 for for computer computer presentation and/or presentation and/or documentdocument camera
camera
Videorecorder/DVD
Videorecorder/DVD playerplayer.. Videorecorder(s)
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.
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.
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),…
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 !
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”
Desktop system
Polycom
Polycom PVX software + PVX software + webcamwebcam Over IP
Over IP
Compatible with
Compatible with NetmeetingNetmeeting
(whiteboard, application sharing, document sharing)
(whiteboard, application sharing, document sharing)
MS Windows + USB connection
MS Windows + USB connection
Usable for very small groups
Usable for very small groups
(maximum 2 to 3 participants for each endpoint)
(maximum 2 to 3 participants for each endpoint)
No
No echo-cancelationecho-cancelation Xmeeting
Xmeeting for Mac OSXfor Mac OSX
videoconference
Roll About system
IP and ISDN H.239
Fast setup in meeting room or connected to existing setup in lecture theatre.
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
Multipoint - MPS200
Media Processing System
Connects up to 20 video sites
(and 16 audio sites)
Gateway between ISDN en IP sites
Continuous presence possibility
MCU = MPS200
ISDN IP Mixed ISDN/IP
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,….)
H-239
Recording the VC (or a lecture)
•
• Recording the VC content on server.Recording the VC content on server.
•
• Streaming to web browsers.Streaming to web browsers.
•
• h.239 support.h.239 support.
•
• Replay using VC endpoints.Replay using VC endpoints.
•
• Replay using streaming.Replay using streaming.
•
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,
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
250 videoconferences each year
250 videoconferences each year
70 multipoint
