View Full Version : Green Screen Video

05-23-2014, 02:17 PM
I was asked by the minister if we could key out the green screen and video without a set in the background. He would like the video to be alpha format where we can use it for something othen than the virtual sets. Not sure what he has in mind, but wants a completely alpha video.


05-23-2014, 03:55 PM
You don't mention which model TriCaster you are running. But if you are on a model that supports it you can capture the video and alpha as two separate clips. Set the AUX output to be the camera input and then at the bottom of the bottom of the list of options for the AUX output, there is 'Alpha Matte'. This will output the alpha on the second output of the TriCaster.

Now you can capture outputs 1 and 2 (PGM/AUX) using the ISOcorder feature to get the video and alpha of that input. Most compositing tools or NLEs can combine the video and alpha clips together.

If the plan is to use the video clips in the TriCaster, then you don't have to bother with all of this. Just capture the video and you can use LiveMatte on the DDR to pull the key when you play the clip back. This can be done on any model TriCaster. If possible, record your clips using a 4:2:2 color space format for best keying results.

05-23-2014, 04:45 PM
Thanks for the info. I forgot the to add the model. It is the 460. Will try what you advised and set it up like that.


05-28-2014, 01:39 PM
As Kane mentioned, you can simply record the video with the green background, using a 4:2:2 codec, and key it later. However, if you do wish to create a video clip with the alpha embedded in it, you can do that in SpeedEdit. It is a free download for 460 owners. Import the pre-recorded green screen clip into SE, key out the green, then export using a Newtek codec that respects alpha. Import that clip into TriCaster and overlay on any background, no keyer needed.


Jeff Pulera
Safe Harbor Computers