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Integrated Services Digital Network (ISDN)

I never knew how ISDN actually worked, apart from the fact it sent digital signals over the the POTS’ copper wires. Wikipedia has a good article about it.

At the moment I am taking two distance education courses (Convex Optimisation and Statistical Machine Learning) which include video delivery through a Polycom video conferencing system. I assumed it used an ISDN link as we had to dial a phone number to connect to the remote site. However it turns out that in fact the Internet is being used (when I pulled up the advanced connection details today). The incoming H.263 video stream’s bandwidth is only 768kbps, which is simply not enough to read the contents of a normal whiteboard at the other end. I could not reconcile the dropped packets and low bitrate with an ISDN link, which would guarantee 2Mbit/s and no such loss in quality – turns out I was right. There are SmartBoards installed, but these haven’t been brought online yet. Apparently the software to make that happen cost the organisers $100,000! That’s unbelievable! Surely there must be cheaper alternatives. And if not, I’ll write one myself (soon)!

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One Comment

  1. I think that video conferencing technology has improved quite a lot throughout the years. For general video conferencing with sound and video, I think it does a pretty good job (also based on the network conditions) but smaller text still pose quite a problem for the systems.

    I don’t know if it is because of the high compression that is involved or because of the lens that is used in these video conferencing systems because the manufacturers assumes that only faces will be broadcasted.

    1. Discount Polycom on May 7th, 2008 at 6:53 pm

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