Firewatch : Web Cameras 101


	Home
	Mission
	About
	FAQ
	WebCams
	WebCam 101
	How To
	Getting Involved

	If you have comments, questions or suggestions for content, or to submit content please email mcf@mric.coop

WebCam 101

The information on this site is specifically targeted at "snapshot" style camera usage (perhaps updating it's image every 30 seconds, or number of minutes) not continuously streaming video. The primary difference being the amount of data that is generated and distributed. Streaming video on a typically static image is overkill. A snapshot image that is updated within minutes is sufficient to capture the essence of the scene at that time of day.

Snapshot WebCams

Snapshot webcams typically generate a single image (as .JPG or .GIF) each time period. This image is typically not large, and even a small image can be impressive to the human eye (on a computer screen). The DivideView Camera generates images at roughly 40K each.

Typical Architecture

Most snapshot webcams rely upon traditional World Wide Web techniques to present images to remote users. A remote web browser is directed to the image using a standard URL (a web address) and then uses HTTP (Hypertext Transfer Protocol) in order to download the image. Remote users of snapshot webcams need no special software in order to view these images.

In short, there is nothing "high tech" about the client side of using a webcam.

Standard Web Browser.

Automatic Refreshing

The HTML page that displays the image typically has the following HTML included. This tells the browser not to cache the page, and to re-load the page every 30 seconds. This allows the client to automatically refresh the image:

  <html>
   <head>
	<meta HTTP-EQUIV="Refresh" CONTENT="30">
	<meta HTTP-EQUIV="Pragma" CONTENT="no-cache">

Typical Setups

There are three typical setups that are used for snapshot webcams, each with pros and cons.

Standalone WebCam (no host computer)
WebCam with Server Host Computer
WebCam with Client Host Computer

Standalone WebCams

These are the simplest type of webcams, typically one plugs them in to a power source, and they just "go". These webcams have an "HTTP Server" built into them, and remote browsers simply connect to that server, inside the camera. These webcams often have a limited number of concurrent users (e.g. 4).

Cons: These webcams require a public IP address (which is not the typical installation on the MRIC network). Public IP addresses require extra care and attention, and are open to the Internet.

WebCam with Server Host Computer

In this setup the webcam is connected to a host computer (PC/Mac/Linux) and is controlled by that computer. Images from the camera are stored as a file within the computer, and that computer is responsible for being the HTTP server. Remote browsers connect to the computer in order to download the latest image.

What is good about this scenario is that computers typically have powerful HTTP server software, and are easy to manage/maintain and control. For users who are comfortable managing their own HTTP server this is a good approach.

Cons: These require the server to have a public IP address.

WebCam with Client Host Computer

In this setup the webcam is connected to a host computer, but that computer passes on the image to a central server in order for it to server it. In this case the client computer uses FTP (File Transfer Protocol) to the server, and hence does not need to be public itself.

Cons: These require software to push the image to the central server. Network traffic (despite being low) is used even when nobody is viewing the image.

WebCam Logistics

When a webcam is housed inside (e.g. looking out the window) many of the logistical obstacles are removed/reduced. A good power source is available (with no risk of problems from the elements), and wiring

WebCams mounted outside often have the most spectacular views, but are subject to the extremes of the elements. Wind, Rain, Snow, Sun -- all can affect the camera.

This document is a work in progress. Feedback and additional content appreciated.