Video Trigger

Free Motion Detector App for Media Artists

Attach a camera and trigger sounds (and more) whenever occupancy is detected in six user-defined areas of the video image. You have complete control over the playback logic and signal routing. Surround is supported. (If you want to trigger a video instead of sounds, see my other app, Video Triggers Video.)

I designed Video Trigger for artists who want to experiment with interactivity without building custom hardware or software. It aims to answer the question that I hear from many of my students:

“How do I make a sound play when somebody walks by?”

The answer often involves micro-controllers (like Arduino), or software (like Processing, pd, vvvv, Isadora, or MAX). In the long-run these options provide much greater rewards, but if you have modest needs, Video Trigger is a painless way to get started.

It works with any Quicktime video input device, like the Apple iSight, DV camcorders, and industrial cameras. Video Trigger can play up to six sound files (AIFF or WAV, 1-16 channels) through any Core Audio sound hardware (1-16 channels) with complete control over signal routing.

NOTE: Video Trigger is not security software. It won’t email you when somebody breaks into your house. Try iSpy, BTV Pro, SecuritySpy, or Blue Iris. 2012 UPDATE: Video Trigger can now trigger an Apple Script or shell script, launch an application, open a file, etc. whenever a zone is entered or exited. See the guide for details.

VPT (Video Projection Tool) is a free app by HC Gilje that handles all kinds of complicated video projection tasks (cueing, mixing, effects, keystoning, etc…). He made a VPT extension based on Video Trigger so you can use a camera to trigger any VPT function.

Sometimes video motion detection is a complex and unreliable way to detect people. A simple floor switch or motion detector attached to a Sparkfun WAV Trigger, hacked computer keyboard or Makey Makey board could do the job nicely. Applications like the (free and wonderful) Soundplant will play sounds whenever a key is pressed, with fine control over the playback logic.

Download Current Version

2013-03-28 (Mac Intel, Not Compatible with PPC Macs)

March 28, 2013, 20MB with MAX6 source patches.
Please read the Video Trigger Guide for instructions and a detailed Changelog.
You may need to adjust your security settings and/or install Java. See Installation Instructions.

There is no Windows version (details).


  • Fixed a nasty bug that was preventing users from selecting any audio devices except “built-in audio”. Oops!

Known Bugs in this version:

  • preferences problem for output channel routing: The first 2 channels of any audio interface will behave as expected (zones routed to these channels will still be routed there when the app is restarted). But, zones routed to channels 3 and higher will “forget” their routing when the application is restarted.
  • 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.
Like Video Trigger? Donations are appreciated. (sorry, not tax-deductible)

Old Versions

2012-08-11 (Mac Intel, Not Compatible with PPC Macs) Aug 11, 2012, 20MB with MAX6 source patches.
2009-01-10 (Mac Intel/PPC) Jan 10, 2009, 17MB with source “patches” for MAX5. (Tested with Mac OS 10.5 Leopard.)