I’ve been interested in videoconferencing for some time, both what it works well at, and what it doesn’t do well. Of late, many have believed that quality makes a big difference, and HD systems, such as very expensive ones from Cisco, have been selling on that notion.
A couple of years ago Skype added what they call HQ calling — 640 x 480 at up to 30fps. That’s the resolution of standard broadcast TV, though due to heavy compression it never looks quite that good. But it is good and is well worth it, especially at Skype’s price: free, though you are well advised to get a higher end webcam, which they initially insisted on.
So there was some excitement about the new round of 720p HD webcams that are coming out this year, with support for them in Skype, though only on the Windows version. This new generation of cams has video compression hardware in the webcam. Real time compression of 1280x720 video requires a lot of CPU, so this is a very good idea. In theory almost any PC can send HD from such a webcam with minimal CPU usage. Even the “HQ” 640x480 line video requires a fair bit of CPU, and initially Skype insisted on a dual core system if you wanted to send it. Receiving 720p takes far less CPU, but still enough that Skype refuses to do it on slower computers, such as a 1.6ghz Atom netbook. Such netbooks are able to play stored 720p videos, but Skype is judging them as unsuitable for playing this. On the other hand, modern video chips (Such as all Nvidia 8xxx and above) contain hardware for decoding H.264 video and can play this form of video readily, but Skype does not support that.
The other problem is bandwidth. 720p takes a lot of it, especially when it must be generated in real time. Skype says that you need 1.2 megabits for HD, and in fact you are much better off if you have 2 or more. On a LAN, it will use about 2.5 megabits. Unfortunately, most DSL customers don’t have a megabit of upstream and can’t get it. In the 90s, ISPs and telcos decided that most people would download far more than they uploaded, and designed DSL to have limited upload in order to get more download. The latest cable systems using DOCSIS 3 are also asymmetric but offer as much as 10 megabits if you pay for it, and 2 megabits upstream to the base customers. HD video calling may push more people into cable as their ISP. read more »