Chroma Key Live


Free Real-time HD Green-Screen Software

Chroma Key Live “keys out” selected areas of live video, allowing a background to show through.  It features Syphon I/O, HD resolutions and full GPU acceleration.


A few years ago, some of my students were doing a green-screen shoot and needed to visualize the chromakey while shooting, so their actors could see the composite while they performed. We didn’t need the advanced features of professional software like Veescope, Wirecast, BoinxTV, VirtualEyez, or Visual Communicator so I made my own solution.

Chroma Key Live performs a basic realtime chromakey (AKA “greenscreen”) on your computer screen, in SD or HD resolutions, with adjustable tolerance and edge fade. The foreground and background sources include Quicktime inputs (ie webcams, DV cams, capture cards…), Syphon Streams, and Quicktime media (movies, stills). The foreground and background layers can be independently scaled, positioned, and mirrored (so your actors don’t see themselves backwards). The playback of Quicktime media can be controlled from the keyboard for easy cueing and rehearsal.

Some background…

In the days of analog video, chromakey was accomplished in the TV studio in realtime. The camera’s live signal would be routed through a keyer in the control room and delivered back to an on-set monitor. This way, the production team could see exactly how the actor looked when composited over the background image. Of course, you would need an expensive studio or at least a video mixer.  Now, in the digital era you can add chroma key effects in post-production using inexpensive software. But they can’t be easily visualized during production. How do you shoot a complex green-screen scene when all you see is an actor against a big green wall?  Chroma Key Live makes it simple again. Run the output from your camera into a Mac, then click on your background and it will disappear, revealing the movie or still image of your choice. Switch to full-screen and call “action!”

Camera Compatibility

The previous generation of digital video cameras recorded to DV tape and could stream their signal in realtime over a Firewire cable. Contemporary HD cameras record onto memory cards instead of tapes, and there is no standard for live streaming of HD video frames over Firewire or USB. Nevertheless, there is hope!. See the Camera Compatibility page for complete info.

Download Current Version

2013-01-19 (Mac Intel, not compatible with PPC Macs)

January 19 2013, 22MB with source “patches” for MAX6.
Please read the Chroma Key Live 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).

General Caveats

  • It cannot record. It strictly displays on the computer screen for on-set preview. You can do much better chroma keys in post-production software! BUT: Since Chroma Key Live now acts as a Syphon Server, you can record the output with the free Syphon Recorder or any other Syphon-enabled app.
  • It cannot chroma-key your camera signal while sending it to other applications.
    Try CamTwist or VirtualEyez for that. BUT: Since Chroma Key Live now acts as a Syphon Server, it will send its output to any Syphon-enabled app.

Changes in this version:

  • Fixed major bug in Camera Input selector that kept most cameras from showing up on the list of available devices!

Bugs in this version:

  • The mouse pointer is displayed when in full-screen mode. (Move it to the side of the screen if this bothers you.)
  • If Syphon Input is selected, but no Syphon servers are found, strange artifacts can appear.
  • Fullscreen only works on the primary display.
Like Chroma Key Live? Donations are appreciated. (sorry, not tax-deductible)

Old Versions:

(See the Chroma Key Live Guide for changelog.)

2012-07-27 (Mac Intel) July 27, 2012, 22MB with source “patches” for MAX6. (Tested with Mac OS 10.6 Snow Leopard.)

2012-03-05 (Mac Intel/PPC) March 5, 2012, 19MB with source “patches” for MAX/MSP/Jitter 5. (Tested with Mac OS 10.6 Snow Leopard.)

2010-12-03 (Mac Intel/PPC) Dec 03, 2010, 19MB with source “patches” for MAX/MSP/Jitter 5. (Tested with Mac OS 10.5 Leopard.)

2009-11-03 (Mac Intel/PPC) Nov 03, 2009, 16MB with source “patches” for MAX/MSP/Jitter 5. (Tested with Mac OS 10.5 Leopard.)

2008-12-16 (Mac Intel/PPC) Dec 16, 2008, 16MB with source “patches” for MAX/MSP/Jitter 5. (Tested with Mac OS 10.5 Leopard.) This version used the CPU instead of the GPU, so it will work on an old PPC Mac Mini with Intel GMA graphics.