Table Of Contents

• Part 1 – Introduction
• Part 2 – Hardware
• Part 3 – Base OS
• Part 4 – Prerequisite Software
• Part 5 – Zoneminder
• Part 6 – Configuration
• Part 7 – Conclusion

In this section we describe the hardware used for the project.

Processing Overview

Before we discuss the individual hardware components, let's go over the specific tasks the system must perform. Typical surveillance cameras create analog video signals. I most cases you could hook one of these cameras directly to your television video input and watch it. To get this signal into a computer for processing and saving, we need it converted to digital information. That is the job of a video capture card.

The surveillance application will use the capture card to acquire images. At a minimum the application will make the images available for viewing on a monitor or the web. The application we're going to use keeps a buffer of the most recent images and compares them to detect motion. If motion is detected then it saves the images to the hard drive. It will also maintain a list of such "events" that you can search and display.

Other than the capture card this processing can be handled by typical PC hardware. It would be nice to view the cameras on a television so some tv-out capability would be nice. Here is the hardware list for the project.

Hardware List

Our video surveillance system uses the following:

Case:	Casetronic C-137
Motherboard:	VIA EPIA M10000
CPU:	C3 w/ Nehemiah core
RAM:	256 mb
Hard Drive:	Seagate Barracuda 80 gb
Video Capture:	Adlink RTV24 4-port capture card

Of course we'll also need four surveillance cameras. We don't have particular models in mind for this project but will give some suggestions later in this part. We have a Digital Surveillance Hardware Kit with all of the above hardware conveniently packaged together. Check it out!

The Motherboard

VIA has a series of motherboards and CPU's positioned for use in embedded and digital media applications. They are noted for their low power requirements, low heat, and low noise. While a video surveillance system will likely be tucked away where noise isn't a problem, it is something that will run 24x7 so low power will reduce its operating costs. We are using the VIA EPIA M Mainboard with the C3 Nehemiah processor operating at 1ghz. Unlike some VIA CPU's, the C3 requires a CPU fan.

This CPU will easily carry the load of our four camera video surveillance system. Even watching all four cameras simultaneously and with the system performing motion analysis, the CPU is about 45% idle.

The M10000 motherboard has hardware support for MPEG decoding. That is not a feature we will need for this project. While the software we're going to use can transcode motion events into MPEG files, that is for remote viewing and not for display on an attached monitor or TV where VIA's hardware would help.

The VIA EPIA M Mainboard includes a TV-Out connector so we can connect our system directly to a television. We will use this feature to display live feeds from our surveillance cameras on a TV.

Memory

The application we're going to use has moderate memory requirements. 256mb appears to be just enough to avoid swapping. So our system will have 256mb of RAM.

Hard Drive

As I've mentioned elsewhere, I prefer Seagate hard drives. Seagate was the first (to my knowledge) to focus on reducing noise in hard drives. They first delivered Fluid Damping Bearings in their drives for quiet operation. Seagate also has some of the longest warranties for consumer hard drives.

The surveillance system stores images when motion is detected. You'll need a reasonable amount of hard drive space to store these. Since we're unlikely to accumulate events over long periods of time, the amount of hard disk space we'll need is modest.

Here are some calculations. An event is captured as a series of jpg images. Each of these images runs about 10k on my system. The duration of an event could easily include 50 to 100 or so images. Assuming 100 images this give us about 1mb per event. My fairly busy driveway triggers about 50 events per day. The other cameras have fewer. But figure worst case at 50 events per day times 4 cameras times 1mb per event and we have 200mb per day as a rough storage requirement. An 80gb hard drive, assuming 70gb available after OS and application installation, would hold nearly a year's worth of events. Thus we'll use an 80gb hard drive in our system.

Note that with a 3.5" hard drive only one of the Casetronic C-137's PCI slots is available. If you want to use two PCI cards, you'll need to use the smaller 2.5" laptop hard drive. These drives do not have the capacity of the 3.5" drives, are slower, and cost more. One could easily add a second capture card to handle eight cameras. If you choose to do that you will need to use a 2.5" hard drive. Most of these drive use a 44-pin IDE connector instead of the 40-pin connector on the VIA motherboard. You will need to get a 44-pin to 40-pin adapter to use a 2.5" hard drive.

Optical Drive

There isn't any need for an optical drive after the OS is installed. It might be nice to have a CD burner so you could save captured events but the software doesn't currently support that capability. Thus we'll save a few dollars and omit the optical drive from the system. For the OS installation you can temporarily hook up any IDE CD-ROM. It doesn't have to be a slim drive either. Just leave the case top off and set the drive somewhere nearby.

Video Capture

As we discussed above, the video capture card converts our analog video signal from the cameras into digital data. There are a wide variety of capture cards for surveillance applications. Most handle a single camera but some models accept multiple cameras. Be aware though that not all multiple input cards are the same. The less expensive models feed the multiple cameras through a single digitizer chip. The chip digitizes the frame of one camera, selects the next camera, digitizes a frame from it, selects the next camera, and so on. This has a few undesirable implications.

First, since there is only a single chip for all the cameras the framerate for a single camera is limited. As a general rule the digitizing chips you're likely to encounter can handle 30 frames per second. If you have four cameras then the most you'll see is about 7 fps per camera.

The problems go beyond framerate. If you have, for example, four independent cameras, they will not be scanning in sync. When the capture chip switches from one camera to the next, it needs to wait for the camera's vertical sync before it can capture. At best this reduces the overall framerate. It can get worse. I've seen boards that don't deal with camera sync well and give jumpy images. YMMV.

Finally, if you have a single capture chip you cannot independently adjust the brightness and contrast of the cameras. If you have cameras with differing light levels such as internal and external cameras, you'll not be able to find brightness and contrast levels that work well for all cameras. For me this was a deal breaker leading me to look for alternatives.

We definitely want a capture card that handles multiple cameras and one that has a dedicated digitizing chip for each camera. Four cameras per card is our minimum. This doesn't give us many options. Its not uncommon to find cards like these costing upward of $1,000 each. Not within our budget. We did, however, find a little gem from a company called Adlink.

The card we're using is the Adlink RTV24 4-port, real-time capture card. This card has four independent digitizing chips, one for each camera just like we wanted. These are some other features:

• Four color video digitizers operating in parallel
• Up to 120fps in 32-bit with 33/66MHz PCI bus (30fps per camera)
• Color (NTSC/PAL) and monochrome (EIA/CCIR) cameras
• Up to 16 channels extension
• On-board TTL I/O lines
• Built-in watchdog timer

The RTV24 has other features that are only available using the Windows drivers. For example it can be programmed to capture only certain areas of interest instead of the full frame. It can also scale the image down by a factor of 16. Since our system will use Linux, we won't make use of these features.

We have some RTV24 capture cards in stock if you want to purchase one.

Assembly

We'll leave assembly as an exercise for the reader. If you need help there you can jump on the forums and ask for help.

Cameras

We'll have future articles that discuss and compare cameras. This project will work with just about any camera that can output NTSC or PAL video. The software we're going to use can even use network cameras though we won't deal with those right now. When selecting a camera there are a couple things you should watch for - sensitivity and field of view.

Sensitivity is a measure of the illumination the camera needs to capture a usable image. It is measured in lux. Generally black and white cameras will have better low light sensitivity than color cameras.. If you're interested at all in capturing images at night you'll want a camera with at least 0.1 lux sensitivity. Lower is better.

Some cameras will advertise a minimum illumination of 0 lux. These are black and white cameras that have infrared LED's for extra illumination. These are ok but the infrared illumination is limited to a few feet. If you want to capture a big area like a driveway, the infrared illuminators won't do much good. Its better to look for a camera that has a good unassisted low light sensitivity.

The other thing to look for is field of view. Most inexpensive cameras have very narrow fields of view. Think about it. If you want to put a camera in the corner of your living room, you will need about a 90 degree field of view to see everything. Few surveillance cameras have a field a view that wide. Another place where you'll need a wide field of view is in cramped spaces like around your front door. In a situation like this the camera will be fairly close to the subject. If it has a narrow field of view you're not likely to see much more than belly buttons and arm pits. As a general rule cheaper cameras have narrower fields of view. I look for cameras with a field of view of 60 degrees or more for general "around the house" surveillance.

Next: Installing the Base OS

History
30 June 2005	Initial Publication

Tim

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Published on: 2005-06-30 (6045 reads)