Starting with version 0.9.8, QuickSnap has the ability to sense changes in its images. This means that you can now record a movie frame whenever the scene changes. Using this feature you can log all the visitors to a location. Combined with the time-stamping option, this provides some interesting security possibilities...
Version 1.0.3 introduces another option. You can make QuickSnap refresh its memory after N frames. Setting N to zero switches this option off.
This document describes how to use QuickSnap to do this.
If you have not registered your program, QuickSnap's movement detection feature is limited to 10 movements (no matter how long they are apart). This restriction is removed when you register and pay your US$25 shareware fee (I have to eat).
Step 1 : Set up QuickCam
Make sure your QuickCam is operating. The best way to check this is to run the QuickPICT program supplied by Connectix. If the QuickPICT program runs, then so should QuickSnap.
Step 2 : Launch QuickSnap
Launch in the usual manner and you should see the viewfinder window appear with the Camera scene therein. Adjust the size of this window to accomodate the area you are interested in monitoring and make sure you QuickCam is pointing at the desired location.
Step 3 : Set up the movement settings
There are three settings which directly affect the images; both lie in the "movement settings" dialog (accessed fron the Video Menu). They are "Motion Threshold", "time between frames" and "Audio Alert". Time between frames is the interval between successive images which will be examined for motion (I recommend using at about 5 seconds here to allow QuickSnap time to adjust the exposure when the light intensity changes).
Movement Sensitivity is a threshold above which QuickSnap decides movement has occured (I recommend a value in the range 20 - 40 here). The last motion score is drawn in the lower left of the viewfinder window when the camera is recording in security mode -- you can watch this value to decide on a motion sensitivity suited to your needs.
Audio Alert allows you to switch on a noise when movement is detected. For those who like to fiddle, the sound for the Audio Alert is stored in a 'snd ' resource with ID 202. You can use ResEdit to paste a new sound in here if you would like something more amusing.
Step 4 : Choose A Video Compressor
Choose "Video Compression..." from the Video Menu to change these settings. These settings are preserved in the application preferences so you need only set them once. If you want small size images, I recommend the Cinepak compressor at low image quality. For high quality images, the animation compressor is lossless and fast.
Version 1.0.1 and later has sequence compression. This makes the resulting movies much smaller at the expense of more processing time. I recommend you use a key frame every 4-12 frames. The compression time determines the minimum interval you can have between successive frames. If you wish a faster response at the expense of disk space then use the animation compressor. With a quality setting of 10% cinepak produces movies which are one fifth the size of animation compressed movies.
Note that the Frame rate specified in the compression dialog is the playback frame rate and not the rate at which frames are taken by QuickSnap. I suggest using the value of 10 here. The films should then play back at a rate of ten frames per second.
Step 5 : Start Recording
To start recording with movement detection mode choose "Security Cam" from the video menu. Whenever movement is detected above the movement threshold, an image is taken and added to the movie. The movement threshold is calculated by summing the differences between the current image and the previous image. If the average difference is greater than the threshold then movement is defined to have occurred.
Step 6 : Finish Recording
To finish recording either Quit QuickSnap or choose "Stop Recording" from the Video Menu (Command R). The movie is stored in QuickTime format and can be viewed by any quicktime movie player. If double clicked it will start up the QuickMooV application provided by Connectix.
Step 7 : Pay Shareware Fee !
QuickSnap has a built in limit of 10 movement frames. That means that using movement recording, you are limited to 10 movements (no matter how long they are apart). This restriction is removed when you register you program and pay your shareware fee (I have to eat). The shareware fee is US$25 and for this you will get a nice letter, a warm fuzy feeling of virtuousness, and a registration code which will remove the frame limit (and will work with future updates). If you are in a hurry, send me the registration form by email, or better still register using compuserv, promise to send me the fee and registration can be done by email (tim@jurgen.physics.utoronto.ca).
