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The working method of
the most Webcams is basically quite simple. A
video camera is connected to a computer. A
specific program now makes an upload of a new
picture in the Jpeg format by ftp, always after a
specific space of time onto a server. The older
picture is retyped again and again by the newer
picture. If a visitor visits the Webcamseite, his
browser downloads this picture and places it in
the window so the visitor can see it. A
Java-Applet (application which is written in the
programming language Java) gives the instruction
to the browser of the visiter such as the
Netscape navigator or Microsoft Internet Explorer
to download the picture in a defaulted space of
time again and again, and to place it in the
browser window. The older picture is also
retyped, so the visitor see the new picture.
Requirement for it is of course, that the
browsers of the visitors also support Java, what
the case is of newer versions of browsers.
The kind and manner of the Picture crossing of
the older one to the newer picture depends on the
Java-Applet. The refresh is abrupt in the case of
simple Java-Applets, the refresh occurs in the
case of Java-Applets programmed more extensively
as a cross-fade effect.
The values for the space of time of a refresh are
bigger than 10 seconds. It is not reasonable to
choose a value under 10 seconds, because the size
of a Webcam picture is ca. 15 kb, and those must
be uploaded each time by the Webcam in the chosen
space of time, and are downloaded of the visitor. |
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