Technical Knowledge

Switcher Breakdown The Features of Switcher You Should Know About

Switcher Breakdown The Features of Switcher You Should Know About

Dec 12 2018

In live video production, the video switcher selects between several different video sources, and in some cases, composites video sources together to create special effects.  A professional switcher should enable the director to switch camera images quickly and precisely so that the audience never misses any exciting moments.  Ever wonder what the must-have features in a professional video switcher are?  The following article will introduce the key features in simple terms to help you better understand the switcher.

WIPE Effect

If a WIPE Effect is used, when the video transition happens, one shot replaces another by traveling from a corner or an edge of the screen to another or with a special shape.  WIPE Effects are similar to using a paint knife on the canvas.  The most common WIPE Effects are horizontal and vertical WIPE.  Other WIPE Effects are named according to their transition styles, such as diagonal wipe, iris wipe, heart wipe, and matrix wipe. 

MIX Effect

The MIX Effect refers to a video transition where two videos overlap each other in a soft and mild manner.  The MIX Effect is also known as the cross-dissolve effect which gives viewers a feeling of elegance and conveys sentiments in the program. Thus, the MIX Effect is usually applied in slow or emotional scenes.  Additionally, the director is able to configure the length of transition time either by key-control or by using T-bar manually to customize the transition timing.

Chroma Key

Chroma means “pure color”, and “key” is a technical term for removal. Chroma key thus is a process of removing a particular pure color from the image and then overlapping the resulting image on top of a pre-configured background image. Theoretically, all pure colors can be removed. Therefore, all colors on the talent must be distinguished from the background color. Green and blue backdrops are the most common adoptions for studios because the two colors are the furthest from human skin color, leading to easy keying and low error probability.

Chroma key has been widely used in many studio applications such as news programs, television drama series and movies with special effects.  Thanks to chroma key, the production team does not have to travel far or risk their lives to capture stunning images.  All they need is to shoot the talent against a green or blue backdrop in the studio, and then the backdrop image will be keyed out and replaced by a preconfigured background.  By applying chroma key, the producer will be able to create the most immersive visual experience.  Chroma key makes it much easier to create movies and TV shows, and it is also cost-effective. 

Luminance Key

The aforementioned chroma key utilizes the technique of color removal, but luma key removes the background based on the luminance of an image.   Before we talk about luma key, we should understand the idea of “luminance” first.  Red and green are contrasting colors in chroma, but the brightness of the two are similar when they are converted to grayscale.  As for black and white, they are at the opposite sides of the brightness scale, thus yielding a better luma key result compared to gray.

Luma key removes the darkness of a color while keeping the lightness of another complimentary color. As a result, the greater the contrast of the complimentary colors, the easier it is to create a good luma key effect.  Luma key is a very common adoption for making subtitles, and the feature of luma key usually found in professional switchers only. 

Downstream Key

Live news footage is typically made of at least three stacking image layers – the underlying background image (eg, virtual background), the middle layer of the mask image (eg, talent in the studio), and the outermost foreground image (eg, subtitles). 

Downstream key (or DSK)  is the control for displaying the outermost image layer (i.e. the top layer of the image).  The director can use downstream key to insert subtitles, logos, or other images into the  live video, and the DSK layer will remain on the screen even after background image and video input sources are changed.  Downstream key is an essential feature of any professional switcher.  The more DSKs a switcher has, the more channels that the switcher can control.


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