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Key and Fill Workflow

 1 Minute



Key and Fill Setup


Content comes in various forms. A lot of the time content is being distributed with so called alpha channels. This allows the content to be transparent through the alpha channel. Depending on the video chain and the technical setup, Pixera may play out into a system that does not recognize alpha directly.

To be able to utilize alpha it is mandatory to setup the media server to be able to play out the so called “Key” and “Fill” signal. 

The Fill signal is the regular content without alpha as the receive system cannot play out the video with its alpha channel. The Key signal is the alpha portion of the video. It is the content transferred to a greyscale in relation to its luminance. 



Setup in Pixera 


We start by setting up two Displays. Alternatively, an LED screen can be used as well:




For a better overview rename the screens to “Key” and “Fill”. 

It is important to activate “Target with Alpha Channel” for both Screens. This option adds alpha to the screens themselves. Normally when reducing the opacticy of a layer to zero there is no “see through” and a black screen will be displayed. By adding this options it is possible to fade out layers / timelines or content in general with alpha. This setting therefore is mandatory:


Let's change to the mapping tab and add outputs to the displays:


On the “Key” display we must activate the following option:


By selecting this setting Pixera will convert the signals alpha to a greyscale.



In the mapping tab the same content was added to both screens. Furthermore, the layer names were changed:


In the preview everything looks as usual. Now let's look at the outputs.







Feed both output signals to the desired image processing unit where they can be again combined in order to generate a video signal with alpha.



This only works when using content with added alpha channel. On regular content this setup won't work. Please always check the content via different tools (for example media info or Pixera) for alpha channels:





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