Webcam32 Image Pull


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Webcam32 Image Pull

What is Image Pull?

Webcam32 has the ability to send streaming images directly to the browser using Server Push. Server push sends one image after another as quickly as possible. Unfortunately, only Netscape supports Server Push natively and so the JavaCamPush Java Applet is required for Internet Explorer.

With the modern Microsoft Internet Explorer (V4.0 and above), a language called JavaScript was added. JavaScript is the ability to embed simple programming logic in the HTML of a web page itself. When the web page is downloaded by the browser, the browser can interpret the script.

This page shows a new way to provide streaming video without requiring a Java Applet. The new technique is called Image Pull.

For extra help in setting up the Image Pull technique, please see the Image Pull Tutorial.

How does Image Pull work?

The following diagram helps illustrate how image pull works. See the description after the diagram:

Image Pull design

Step Description

1 The end user starts a browser (Internet Explorer) and targets the web page at the Webserver that hosts the Webcam32 Image Pull HTML and Java Script

2 The Webserver sends the HTML file back to the browser for display. The HTML contains Java Script in addition to other HTML tags

3 The browser interprets the Java Script. The Java Script requests that an image be obtained directly from Webcam32 using the single frame technique. The Web page contains the TCP/IP address of the PC hosting Webcam32.

4 The request arrives directly at Webcam32 and a single frame (a still JPEG image) is requested and returned.

5 The image arrives back at the browser and is displayed. The moment that the image arrives at the browser, the Java Script code in the page immediately requests a new image and the path from step 3 is repeated.

Sample Image Pull page

The preceding technical discussion of using the Image Pull video streaming technique need not be understood in order to use this mechanism. A sample page has been provided HERE which may be used as a template.

Please note, technical support will be provided on the usage of Webcam32 and Image Pull using ONLY the sample page. The sample contains much Java Script code and can be easily broken by a user modifying the page. The sample page is designed as a starting place. Make sure that the sample page works perfectly without any changes on your own web site. If changed, no technical support for those changes made by a Webcam32 user will be provided.

Step	Description
1	The end user starts a browser (Internet Explorer) and targets the web page at the Webserver that hosts the Webcam32 Image Pull HTML and Java Script
2	The Webserver sends the HTML file back to the browser for display. The HTML contains Java Script in addition to other HTML tags
3	The browser interprets the Java Script. The Java Script requests that an image be obtained directly from Webcam32 using the single frame technique. The Web page contains the TCP/IP address of the PC hosting Webcam32.
4	The request arrives directly at Webcam32 and a single frame (a still JPEG image) is requested and returned.
5	The image arrives back at the browser and is displayed. The moment that the image arrives at the browser, the Java Script code in the page immediately requests a new image and the path from step 3 is repeated.