Webcam is short for web-camera. A webcam takes repeated
snapshots and broadcasts them over the Internet. A digital camera in contrast
takes a picture only when you click the button.
Webcams typically produce low quality images, one every few seconds, usually at
320x240 resolution. These are called snapshot webcams.
They have the advantage people can access them even if they only have a dial up
Internet connect. Further, your ISP won’t charge you for broadcasting too
many Internet packets.
They work by basically by serving jpg images to the world from the computer with
the camera. The webcam software changes the jpg image every few seconds so that
when people use their browser or a special viewer such as NetworkCam,
to look at it, they see the latest version. The viewer automatically requests a
new image every few seconds. To a browser, the image looks like any ordinary jpg
image, it is just replaced extraordinarily frequently by an updated one.
Higher quality webcams send a continuos stream of images, as fast as the
receiver can accept them. These are called Streaming webcams.
Cheaper ones send jpg images wrapped in an RTP
stream protocol. High end ones send mp3 images, possibly also with sound.
Since most webcam viewers don’t have domain names for their home machine,
you often find yourself fetching such streams from URL that look like this:
http://207.245.67.113/cgi-bin/fullsize.jpg
The catch is the number part, the IP, does not necessarily stay fixed. You need
to use a service like DynDns
to get around this problem, and give your camera a permanent name.
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recommend Amazon⇒Logitech QuickCam Pro 9000 Webcam |
| Rated #1 by Good Housekeeping. I don't know about its Java support. It has a fun feature to convert your image to an animated avatar. It has RightLight to correct poor lighting. I has a Zeiss lens. It unusually good at having no lag in the picture or sound. Records or streams 960 × 720 pixels. Stills at 1600 × 1200 pixels. |
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recommend Amazon⇒Ezonics EZ Video ChatKit |
| Rated #2 by Good Housekeeping. Low cost. Includes a pair of cameras and a pair of headsets. I don't know about its Java support. 352 × 288 pixels. |
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recommend Amazon⇒Fire-i Webcam Firewire Digital Camera By Unibrain |
| Rated #3 by Good Housekeeping. For the Mac, SuSe Linux and PCs. I don't know about its Java support. 640 × 480 pixels. |
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2008-02-01 by Roedy Green ©1997-2008 Canadian Mind Products
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