Webcam32 FAQs User's Guide Java Support Help Wizard
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Webcam32 FAQs User's Guide Java Support Help Wizard |
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Server Push is a technology for streaming live video from Webcam32 onto the web. It is important to review all the details described in this page.
Server Push is a technology pioneered by Netscape and implemented natively in the Netscape Navigator browser. When a browser accesses a Web page to obtain an image, the image is returned to the browser with a header which contains information about the content of the image. This header is in a format called MIME and is understood by all browsers. The MIME information allows the browser to interpret the format and content of the data.
Server Push is an extension to the MIME format information. Instead of a single image being delivered to the browser, the MIME header informs the browser that it should expect a series of images to be received until an end-marker is located in the data delivered from the Web server.
Webcam32 has the capability to behave as though it were a Web server capable of delivering images. To obtain an image from a real Web server, an HTML tag such as
<IMG SRC="http://www.somehost.com/image.jpg">
would be included in the HTML source. This tag instructs the browser to go to the www.somehost.com computer and obtain the JPEG image called image.jpg. For Webcam32, the following HTML tag could achieve the same task:
<IMG SRC="http://www.mywebcam.com:8888/video/push">
Where Webcam32 is running on the machine www.mywebcam.com. Unlike the previous example where the image is stored statically on disk, obtaining an image directly from Webcam32 will result in a new image being grabbed immediately from the camera and delivered to the browser.
In the TCP/IP Access settings for Webcam32, a TCP/IP port will have to be defined for remote access which include Server Push stream access. When a browser requests an image from that TCP/IP port, Webcam32 will start delivering a series of images wrapped in the Server Push MIME formats.
Since each browser that is receiving the images from Webcam32 consumes network bandwidth and a connection to Webcam32, a mechanism must be developed to stop transmission of the images at some point. In the Webcam32 TCP/IP settings, a timed duration and a maximum delivered byte size may be specified. When a client accesses Webcam32 for Server Push images, Webcam32 will end the connection to the browser after either the duration of that particular connection has passed or after the maximum number of bytes transmitted has been passed. Which ever trigger has been reached first will cause the Server Push connection to be ended cleanly. If either value is set to 0 (zero), the trigger will never be reached.
The following illustrates a sample setup of the Webcam32 TCP/IP settings.
| 1. Single frame, Server Push and Applet enabled/disabled selections
2. TCP/IP port number on which Webcam32 is listening for remote access requests.
3. Maximum duration to push a single client. 4. Maximum size to push to a single client. 5. Pause interval in milliseconds between frames sent to the client.
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To enable Webcam32 to accept incoming Server Push requests:
<IMG SRC="http://yourhost.com:port/video/push">
where both yourhost.com and port are replaced by the TCP/IP name or address of the machine running Webcam32 and the port number selected for Server Push.
