ConferenceXP: A Versatile Video Conferencing Tool for the Performing Arts
by Jose Feghali
Bits and Bytes
Computers understand 1 and 0
11111111 = 255 (one byte) smallest unit that a computer can understand; a byte is a unit for information; communication across the internet happens in bits
Bandwidth
When you are sending a signal from one computer to another, you are sending a series of 1s and 0s. Internet “speed” is a misnomer because the speed is always the same; it’s the amount that changes (e.g. water flows at the same speed, but the size of the pipe determines how much water flows through at once).
Internet2 – the sky is the limit!
Normal T1 – 1.5 Mbps up/down
Only I2/NLR have multicast
Modem – started around 300 bps
Really Good Modem – 56 Kbps
“Normal” T1 – 1.5 Mbps up/down
ISDN – 128 Kbps DSL ~ 6 Mbps
FIOS/DOCSIS3/UVerse – >50 Mbps
Internet2 – 100Gbps [!!]
Multicast x Unicast
With unicast, there must be a single connection between each client and the stream source. Multicast, on the other hand, enables the sending of a webcast from a stream source to an Internet mcast “Cloud,” which each client can then tune into – much like a radio. Because there is still a desire to receive payment from those tuning into webcasts, multicasts are not currently extensively used.
Compression
DV Video = 30 Mbps
SD Video = 120 Mbps
HD Video = 1.5 Gbps
HDV Video = 22 Mbps
HD @ Home < 10 Mbps CS Audio = 1.5 Mbps Normal MP3 = 128 Kbps Sound is much more difficult to compress and maintain quality with than video. Required Bandwidth Stereo (2 channel) CD Audio = 1.5 Mbps (need to be able to handle at least this in order to give virtual lessons with quality audio transmission) DVD (compressed) video = 2 to 5 Mbps DV Video = 30 Mbps Variable codec = 50 Kbps to > 50 Mbps
Windows Media (CXP) = 50 Kbps to 5 Mbps
Required bandwidth for good quality work (500 Kbps video + stereo CD audio) = 2300 Kbps or 2.3 Mbps and +
How about MONO? – 1 channel CD quality audio = 750 Kbps (0.75 Mbps)
Required bandwidth for good quality work = 1500 Kbps or 1.5 Mbps and +
Remember…
Max “speed” doesn’t mean average
Major metropolitan centers = jam
Time of day/major webcast event
Quality of line (distance from “box”)
Cable – amount of people on group
Virtually nobody guarantees speed
The more “headroom,” the better!
Read forums and users’ reports!
(http://dsireports.com)
Mr. Feghali then proceeded to give a demonstration of ConferenceXP with a student at his studio in Texas. You can use multiple cameras on each computer. Initially, the sound was compressed, so he worked with Microsoft Research to get the necessary 1.5 Mbps CD quality audio. This is currently the only program in the world that can do this. The program can be used in a professional setting with very high bandwidth and at home with low bandwidth (it will be necessary to send with the audio uncompressed, though). It can also be used with both normal Internet and Internet2. ConferenceXP uses uncompressed audio with compressed video. Amazingly, the software is available for free for educational and research use! Definitely worth checking out!
Links
http://cct.cs.washington.edu
http://cct.cs.washington.edu/downloads/CXP/
Source code: http://www.codeplex.com/ConferenceXP
Forums: http://forums.microsoft.com/MSR/
Wiki: http://cct.cs.washington.edu/project-wiki/
Projects: http://cct.cs.washington.edu/community/
Listserver: cct-announce-request@cs.washington.edu
Also, watch for the forthcoming Classical Geeks website that Mr. Feghali is in the process of developing!
Leave a Reply