Documentation:Modules/bluescreen

Module: bluescreen
Type	Video filter
First VLC version	0.9.0
Last VLC version	-
Operating system(s)	all
Description	change the video's alpha channel
Shortcut(s)	-

This filter can be used in the mosaic framework to set a video's alpha channel (or transparency) based on a pixel's color. This is also known as green screen or chroma key blending and can be used to create effects like on most weather channels.

• bluescreen-u <integer> : U chroma component (0 to 255) default value: 120

• bluescreen-v <integer> : V chroma component (0 to 255) default value: 90

• bluescreen-ut <integer> : U chroma component threshold (0 to 255) default value: 17

• bluescreen-vt <integer> : V chroma component threshold (0 to 255) default value: 17

Example use:

% vlc -I telnet --color -vvv --vlm-conf mosaic.vlm --mosaic-keep-picture \
  --no-audio --sub-filter mosaic

And the vlm config:

new channel0 broadcast enabled
setup channel0 input rushfondvert.avi
setup channel0 output #duplicate{dst=mosaic-bridge{chroma=YUVA,vfilter=bluescreen},select=video}
 
new background broadcast enabled
setup background input redefined-nintendo.mpg
control background play
 
control channel0 play

Have a look at http://people.videolan.org/~dionoea/bluescreen2.mpg for an example of the VLC bluescreen filter. The overlay video is http://people.videolan.org/~dionoea/rushfondvert.avi and features someone with a mask in front of a green background. The bluescreen module's default values are adjusted to remove the background from this video. For other videos you should use your favorite color editing tool to find out the appropriate U and V values.

See also:

• Documentation:Modules/mosaic
• Documentation:Modules/mosaic-bridge
• http://en.wikipedia.org/wiki/YUV