View source for Documentation:Modules/bluescreen

{{Module|name=bluescreen|type=Video filter|first_version=0.9.0|description=change the video's alpha channel}}

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.

== Options ==
{{Option
|name=bluescreen-u
|value=integer
|default=120
|description=U chroma component (0 to 255)
}}

{{Option
|name=bluescreen-v
|value=integer
|default=90
|description=V chroma component (0 to 255)
}}

{{Option
|name=bluescreen-ut
|value=integer
|default=17
|description=U chroma component threshold (0 to 255)
}}

{{Option
|name=bluescreen-vt
|value=integer
|default=17
|description=V chroma component threshold (0 to 255)
}}

== Example ==
 % '''vlc -vvv --vlm-conf mosaic.vlm --mosaic-keep-picture \'''
   '''--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

{{Documentation}}