Chroma Key Live Guide


Supported Cameras

See the camera compatibility page for supported cameras and video input devices.

Connecting Your Camera

Connect your camera to your computer and open Chroma Key Live. Open the “Set Camera Input” window and choose your camera from the device list.

Note that the list shows all the devices your system supports, even if they are not attached! For example, everyone with Final Cut 7 will see DVCPROHD devices, even if they don’t own a compatible camera.

Choose a capture resolution that matches the format of your camera. (It will not detect the native resolution of your video input, sorry.) The video window will change to match the resolution you select. If the window is larger than your monitor, choose the “half” or “quarter” window-size options on the main screen to shrink it down to size.

NOTE: There will be a slight latency between the real world and the image on the screen. The delay time depends on the input type and processor speed.

Choosing Foreground and Background Sources

Chroma Key Live has two layers: Foreground and Background. When the “Show” selector is set to “Composite”, some part of the Foreground will become transparent, allowing the Background to show through. In conventional green-screen situations you want a live camera feed to be composited over a pre-recorded movie or image, so the Foreground “Source” selector should be set to “Camera Input” and the Background should be set to “Movie / Image”.

If you want to process a feed from a Syphon server, click “Set Syphon Input” to choose the server. Then select “Syphon Input” as either your Foreground or Background source. The video window should resize to match the Syphon stream.

NOTE: The resolution and frame-rate of the current Foreground source will determine the properties of the Chroma Key Live video window and Syphon output. The Background source will be stretched to fit.

Syphon Output

Chroma Key Live is a Syphon Server, so it is always sending its output via Syphon to any other compatible applications. (There are no settings.) Expect dropped frames when toggling fullscreen on/off, but the stream will not be interrupted.

There is no recorder in Chroma Key Live. It strictly displays on the computer screen for on-set preview. You can do much better chroma keys in post-production software! However, you can record the output with the free Syphon Recorder or any other Syphon-enabled app.

Mirror, Size and Position

On a typical green-screen set, the performer is facing the camera and the monitor is facing the performer. Their actions will seem reversed, so you can use the “Mirror” option to correct it. (Note: In this case, mirror both the Foreground and Background.)

You can scale and position the Foreground and Background layers. Example 1: You want your actor to fit into a small doorway in your background media. You compose your shot so the actor fills the whole frame. In Chroma Key Live you shrink the actor and position him to fit into the doorway. Your camera footage is full-frame so you get maximum quality and the freedom to make adjustments in post. Example 2: You are shooting with a Canon 5DmkII, feeding the HDMI signal into Chroma Key Live via a capture card. The 5D image doesn’t fill the entire frame but you can scale it up using Chroma Key Live, to match 1080 background media.

Making files for the Movie / Image Input

You can use any QuickTime-compatible file as a Movie / Image Input. Chroma Key Live will stretch your  image to match the current Foreground Layer dimensions. To avoid stretching artifacts, prepare your files in advance so they match the aspect ratio of your Foreground source. (Otherwise, if you’re using Chroma Key Live for on-set preview, your actor’s movements won’t match your background!)

If you’re using Chroma Key Live for on-set preview, keep your background files organized. Break long scenes into different movies so the actor can work on them individually. The audio in your movie will play from the computer speakers. Prepare each movie with a voice-slate or sync beep at the beginning. On-set, let the camera run constantly (with mic on) so it records your audio queues. They will help you sync up your foreground & background in post!

Controlling Movies

Press LOAD to choose your file. Like editing software, Chroma Key Live uses the J,K and L keys for backwards, pause, and forwards. You can also hit the spacebar anytime to play your video clip from the beginning. (Looping is optional.) You can jump to any frame in your movie by dragging or typing in the “Jump to Frame” number box.

Chroma Key Controls

This is where you choose which color (in the Foreground Layer) will become transparent. You can click directly on the video window, or use the color picker. High “Tolerance” values will treat more colors as transparent if they are similar to the color you chose. “Edge Fade” controls the softness of the edges of transparent areas.

Remember that Chroma Key Live is a very basic keyer. Your post-production software will produce a much better key.

Full Screen

Press the “Esc” key at any time to enlarge your image to full-screen. (Press again to return to normal.)

Preferences

All settings are saved automatically to an xml preferences file whenever you close Chroma Key Live. If you want to get really nerdy, you can edit the xml with any text editor (but Chroma Key Live doesn’t monitor changes in the xml while it’s running).

GPL License

Chroma Key Live is Copyright 2008 – 2012 by Zach Poff. It is Free Software, released under a GPL 3.0 license. You are free to copy it, modify it, and redistribute your changes provided that all derivative products remain GPL licensed. The source files are included in the download. (See http://www.gnu.org/licenses/gpl-faq.html for details about this license.)

It contains Syphon external objects which have a separate BSD license (full details included in download).

The software was developed in the (non-free) MAX6 visual programming environment (http://www.cycling74.com) which is required if you want to edit the source code. My application contains the MAX6 “Runtime” environment, which is not GPL, so my license pertains to my contributions only.

Change Log

Version 2013-01-19 (January 19, 2013))

  • 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.

Version 2012-07-27 (July 27, 2012)

  • Dropped support for PPC Macs. (Its a MAX6 thing, not my choice.)
  • Added: Syphon Framework support. Chroma Key Live is now a Syphon Server and Syphon Client, so you can connect it to many other video apps. Hooray!
  • Added: New user-interface paradigm. The foreground and background layers now support scaling, positioning, and mirroring along with arbitrary source selection.
  • Added: There is a link to the Chroma Key Live Guide within the app.
  • Fixed crashing bug when user clicked on screen when in fullscreen mode.
  • Fixed bug in mirroring code.

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.

Version 2012-03-05(March 3, 2012)

  • Added: The new “foreground” selector lets you put your pre-recorded footage in the foreground while the live camera fills the background (the opposite of the typical setup). So certain colors in your pre-recorded file can “knock-out” to reveal the live image.
  • Added: The foreground and background can be flipped separately. (Typically you would flip both or none, but in some installation contexts it’s nice to flip them individually.)
  • Changed the “full screen” key from “F” to “Esc” so it’s easier to find in the dark!
  • Updated the UI so it’s slightly less ugly!

Bugs in this version:

  • Sometimes the camera image is corrupted when the app first opens. Open “Video Settings…” and click on your resolution setting to fix it.
  • The app will crash if you click on the image while in full-screen mode! (You might discover this while trying to choose the transparent color, so please choose your transparent color BEFORE you go to full-screen mode.)
  • The mouse pointer is displayed when in full-screen mode. (Move it to the side of the screen if this bothers you.)

Version 2011-11-08(Nov 8, 2011)

  • Added: The live camera image can now be scaled and positioned. (Example 1: You compose your shot so an actor fills the frame. In Chroma Key Live you shrink the actor and position him to fit into a small doorway in your background elements. Your camera footage is full-frame so you can change your mind in post. Example 2: You are shooting with a Canon 5DmkII, feeding the HDMI signal into Chroma Key Live via a capture card. The 5D image doesn’t fill the entire frame but now you can scale it up using Chroma Key Live, to match 1080 background elements.)

Version 2010-12-03(Dec 12, 2010)

  • Added: background movie can loop now

Version 2009-11-03(Nov 11, 2009)

  • Changed to GPL 3.0 license
  • Fixed: In fullscreen mode, aspect ratio of video is preserved
  • Fixed: In fullscreen mode, menu bar is no longer displayed
  • Fixed: Video input menu redesigned and clarified
  • Added: GPU-accelerated, so frame-rate is much faster even at HD resolutions
  • Added: HD support
  • Added: background filename is now shown in main window
  • Removed: Title Safe / Action Safe Guides because it’s a pain to calculate them for each new resolution

Version 08-12-16(Dec 16, 2008)

  • First Release

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