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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