Video Trigger Guide
Things You Need
STEADY LIGHTING
Video Trigger detects motion by comparing each new video frame with a stored background image. If they match then nothing gets triggered. If they mismatch enough then a zone gets triggered. Therefore, performance is only as reliable as your lighting. If you turn off all the lights then you will trigger all of your zones. It’s that simple. I might include an option for adaptive background someday if somebody asks for it.
COMPUTER
Mac OS 10.4 and 10.5 have been tested. The slowest machine that I have used is a Mac Mini with a single 1.8GHz processor. It worked fine. The sound files are played directly from the hard drive, so you can play long files without eating up too much RAM. Keep in mind that multichannel sound requires a lot of disk access though.
CAMERA
See the camera compatibility page for supported cameras and video input devices.
NOTE: You must use manual exposure if you want Video Trigger to be reliable!
It will work with auto exposure, but if something bright enters the frame then the camera will automatically darken the image. Then all of your motion-detector zones will trigger and you will be unhappy.
TRIPOD
We are trying to detect motion here, so the camera must not move. Duh.
SOUND FILES
AIFF or WAVE format, NOT MP3. These files can be mono, stereo, or up to 16 channels interleaved. VideoTrigger will give you the opportunity to map any channel of each sound file to any output on your sound hardware. If you’re wondering how to get 3 or more channels packed into one AIFF file, I’ve had great luck with SoundFilesMerger from Emmanuel Jordan (free, donation encouraged)
How to Use Video Trigger
Basic Instructions are included on the screen when you run the software. Basically, you memorize the background and draw “zones” over the live video from the camera. Each zone has an options panel where you load a sound file, choose your outputs, and define the logic of the playback. (When somebody enters the zone should the sound play from the beginning, resume from pause, etc.) There are separate options for entering and exiting the zones, so many behaviors are possible.
Auto-Starting:
Video Trigger is designed for gallery installations where the computer will run all the time, or be turned-on daily. It makes sense to start Video Trigger from the Login Items panel in System Preferences/Accounts/(your username). However, I’ve noticed that the OS launches login items before it is finished booting, so the app might initialize strangely. Launch the included Applescript instead, which will launch Video Trigger after a delay.
Preferences:
All settings are saved automatically to an xml preferences file as soon as you make changes. If you want to get really nerdy, you can edit the xml with any text editor (but Video Trigger doesn’t monitor changes in the xml while it’s running).
License
Video Trigger (and its “source code” MAX/MSP/Jitter patch) is released under a Creative Commons Attribution-Noncommercial-Share Alike license, which means that you are free to modify and redistribute it (with attribution) provided that all derivative products remain non-commercial. (see http://creativecommons.org/licenses/by-nc-sa/3.0 It was developed in the MAX/MSP/Jitter visual programming environment ( http://www.cycling74.com ) which will be required if you want to edit the source code. ($$$)
Change Log
Version 2009-01-10 (Jan 11, 2009) (First Release)
Known Bugs:
- When you load a new sound file, the “Choose Outputs” screen will show no connections, but sometimes the old connections are still active. Choose new connections to override the old ones.
- Sometimes if you choose the “Resume Playing” option while a sound is playing, it might not resume properly on the next trigger. Choose “Start Playing” and trigger it once. Then you can choose “Resume Playing” when it’s done.
- “Video Hardware Settings” might show irrelevant information, but it will still work.