Introduction to video capture and
Written by Joe Janson, updated May 22nd 2014
Project lead at Omega Unfold Inc
I have a motion detection project, what do I need to know?
A motion detector system can give your PC eyes, letting it respond to external events by capturing images, or triggering actions. However, there are many different possible setups, not all of them useful to you. You need to carefully identify your needs, and then get tools that are good enough without overkill.
You'll require both hardware and software, and also advice because motion detection and video capture are still emerging technologies and might not be as "plug & play" as you would like.
Hopefully, the following will help you get started….
What does motion detection software do?
Motion detection software captures video from an input device and processes these video images in real-time to find differences between frames. How it responds to these differences depends on what you’ve programmed it to do.
This is usually associated with security systems, however, general purpose motion detection software like Zone Trigger is now available.
Using motion detection Hot Spots for simple computer vision
General purpose motion detection software is intended for the ordinary users by providing simple tools to create all kinds of projects that would otherwise require costly custom hardware. For example, the following applications may give an idea of what such software can provide, at very low cost. These are often things that weren't possible before:
Good general purpose motion detection software should let you determine exactly what kind of motion to look for and then permit a range of responses, e.g. taking pictures, recording videos or sending e-mail notifications. The best software should also be able to analyze the movement itself. Typical operations include:
What kinds of cameras work for motion detection?
USB cameras (“webcams”)Usually called “webcams”, they are the quick solution for connecting a camera to your PC. All you need is the supplied driver software, so you can be up and running in minutes. Better yet, USB cameras are Direct-X compatible and work with almost any video capture software.
However, there are some snags. Although you can connect many webcams to a single computer, they are more or less limited to arm’s reach because a USB cable is not designed for long distance. More importantly, USB cameras vary widely in their quality. Cheap ones don’t always provide clear or accurate images. Artefacts (visible defects) include motion blur and the oddness caused by compressing the image before sending it to your PC. Some also perform badly in poor lighting conditions, providing grainy images and low frame rate.
The good news is that some good quality USB cameras have a high resolution and a fast frame rate video. Some even come with zoom lens (note that an automatic variable focus lens is not desirable as it may introduce movement when auto-focusing). Resolution varies greatly depending on the model, from standard 320x240 to "doesn't fit the screen". Don't let the amount of pixels be your only guide for judging the quality of a camera; the price of the camera is your first clue about the quality of its images.
The Microsoft Kinect is probably the most famous 3D camera, but there are others, such as the SoftKinetic DepthSense. Zone Trigger has a special mode to support 3D cameras. The software will detect not only if something is moving within a certain zone, but also how far away from the camera it should check for motion.
Most 3D cameras are very reliable because they only use infra-red, therefore visible light will not interfere with the motion detection. This is a HUGE advantage. One of the downsides is that most 3D cameras cannot see very far ahead, thus they cannot be used inevery situation. However, they usually have both a 3D and a Color sensor embedded, and it is possible to use both at the same time. DV cameras (“camcorders”) The DV stands for “Digital Video”. Often called “camcorders”, these provide awesome image quality and a fast frame-rate. They are almost always equipped with a zoom lens, and may have desirable features such as night-vision. They are compatible with Direct-X, they should work with most any recent video capture software.
Like USB cameras, DV cameras are connected to your PC with limited cable length, this time Fire-Wire (IEEE 1394). Note that some camcorders can be connected with a USB connector and may have webcam drivers available. Most new camcorders can also be connected to a PC using a HDMI connector , if your PC is equipped with a HDMI capture adapter.
IP cameras (“network cameras”)Often known as “network cameras”, they are more complex remote-controlled devices that connect to a network instead of directly to your PC. Some can supply very high-resolution images, often with superior image quality, however the price difference is very steep between a normal IP cam and a hi-resolution one.
IP cameras are not physically connected to your PC since they can broadcast video over a local network (CCTV) or the Internet. Most have embedded web-servers, and some have internal motion detection systems. They are now usually wireless and will connect directly to your Wifi network.
Usually lacking Direct-X drivers, they rarely work with motion detection software unless it specifically supports them. I usually recommend Axis IP cameras and Foscam as they use a standard http protocol, and some models even have optional Direct-X windows drivers for optimal compatibility. Zone Trigger has been tested with Axis and Foscam network cameras (but not Foscam H264 models).
Analogue cameras belong to a whole different world. They are fast, provide images with no compression, no artefacts, little motion blur, and use any cable length you need. They may be equipped with a zoom lens or infra-red vision. Some are even “wireless” (but watch the reception quality, since local interference might compromise motion detection). The downside of analogue cameras is that they are complicated to connect, and they are resource-intensive. Connecting one to a PC requires video capture hardware. Many analogue cameras produce interlaced images, requiring special, often 3rd party software filters, which may introduce artefacts or reduce picture quality. Overall, using an analogue camera requires a more powerful computer than a standard USB camera would.
The compatibility of the motion detection software is dependent on the video capture device. Here are a few capture device types:
What are good conditions for motion detection?
In the best conditions you must have the following:
What is Zone Trigger, and what can it bring to my project?
The Zone Trigger software series is all about enabling anyone to incorporate motion or sound detection in their custom projects. This software can be downloaded and installed in less than a minute, and you can setup a custom system in just a few more.
On detecting motion, Zone Trigger can do a multitude of tasks, such as play sounds, run programs or commands, take control of other software or hardware, send email and files over the internet. Plus it has many extra features such as archive services and a built in HTTP server for remote viewing.
Zone Trigger can save you time, money and effort:
Good luck with your project!
http://www.zonetrigger.com - Motion Detection software download site, download a trial copy of the Zone Trigger software.
http://www.axis.com/ - Network cameras
http://www.foscam.com/ - Network cameras
If you have questions about the Zone Trigger products or if you require consultation and advice on your computer vision projects, please contact Omega Unfold's technical support: firstname.lastname@example.org
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