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VIDEO KEYERS

Introduction:

The VJX16-4 has 4 totally independent video KEYERs which allow you to control the Alpha component on each track. The Alpha component manages the transparency of an image and allows you to select areas to make transparent.

The Keyers let you define and choose which color or range of colors to erase or make transparent.

3 different types of Keyers are available, that select which pixels to modify based on varying criteria:

  • ColorKeyer: Chooses which pixels to erase based on their color (or on their R, G, B components).
  • ChromaKeyer: Chooses which pixels to erase based on their hue (or on their chrominance Cr, Cb).
  • LumaKeyer: Chooses which pixels to erase based on their luminance (or on their Y luminance).

The Keyers also have 2 more controls:

  • Tol: The tolerance allows you to make the Keyer more or less selective.
  • Tran: The transition allows you to make the Keyer more or less sensitive and to soften the contours.

The VJX16-4 offers 3 additional modes which allow you to use one of the 3 R, G or B components of the TrackIn as an Alpha component and to use it as a mask.

  • R Mask
  • G Mask
  • B Mask

Configuration:

To configure the Keyer, use the controls from the Keyer section (the 6 buttons Type, In. Track, Pick Mode, On, Inverse and Pick) along with the following shared controls:

Here are the different stages in configuring a video Keyer:

1. Selecting a track:

First of all, choose the video track on which you wish to configure with the video Keyer . To do this, press the SELECT button of the track which you desire (see SELECT FUNCTION chapter).

To configure the video Keyer, press the Type button. This button will light up green and the LED screen will indicate the configuration set-up of the selected Keyer:

  • On the 1st line, the type of Keyer used is shown (ColorKeyer, ChromaKeyer...).
  • On the 2nd line, the number of the input of the Keyer is shown: In Track (by default the selected track). It also shows if the video comes before or after the color effects (PreFx / PostFx).
  • On the 3 rd line, the values of the following parameters are indicated:
  • Tolerance (Tol)
  • Transition (Tran)
  • On the 4 th line, details about which colors have been modified are shown:
  • Red, Green and Blue for the ColorKeyer,
  • Chroma Red, Chroma Blue for the ChromaKeyer,
  • Luminance for the LumaKeyer.

2. Preview:

One preview point is dedicated to video Keyers. This allows you to adjust the Keyer before activating it.

We advise you to configure one of the 3 outputs in preview when you define the parameters of a video Keyer. If one of the 3 outputs is in automatic preview mode, it will automatically switches to the Keyer preview of the selected track once the Keyer selection has been made. Otherwise, refer to the VIDEO OUTPUTS chapter for advice on how to use the preview Keyers.

The following example shows how to preview the video Keyer of track 2 through the OUT 3 output:

  • Configure the OUT 3 video output in preview (see the VIDEO OUTPUTS chapter).
  • Keep the Out 3 button pressed down (one of the buttons on the 4*4 will light up red) and press the button on the 3rd line which corresponds to the track which you want to preview.

Keyer Preview of track n°2
  • The LCD screen also indicates information about the preview:

  • With the OUT 3 output, you will see:

Preview of a ChromaKeyer

The 2 lateral bands indicate the colors which will be made transparent:

  • The precise color which is extracted with a ColorKeyer.
  • The range of the colors which are extracted with a ChromaKeyer.
  • The luminance of all of colors which are extracted with a LumaKeyer.
  • With Red Mask, Green Mask and Blue Mask modes, these bands are respectively red, green and blue.

3. Choice of Keyer types:

Choose the type of Keyer by pressing several times on the TYPE button.

4. Choosing the color:

2 available options:

  • The choice of color can be made automatically with the cursor. For this:
  • Press the Pick Mode button until the light comes on. A flashing cursor will appear on your preview screen.
  • Use the Trackball to move the flashing cross to the area of the image where you wish to delete the color.

  • Press the Pick button until the light comes on. In this instance, the VJX16-4 will analyze the color which it finds under the cross and will only delete that color in the whole video.

  • If you wish to keep this color, press the Pick button again until the light switches off. The table will then memorize the last color selected by the pick.

Helpful Hint:

Using the cursor in real time (illuminated Pick button) is ideal for applications on the background (blue/green screen) where the luminance varies (ex. shadows cast on background by moving objects or actors ...). The VJX16-4 acts instantly on this and automatically re-adjusts its Keyers without user intervention.

  • The choice of the color can also be made manually. For this:
  • Press the Pick Mode button until the light switches off.
  • Use the TrackBall to chose precisely the color that you wish to delete. Here is the organization of color spaces with the Trackball according to the type of Keyer used:


Luma Keyer.

Left: Color Keyer. Right: Chroma Keyer.

Use the 2 vertical bands of color as well as the LCD screen to help you to choose the exact color.

5. Tolerance / Transition parameters:

The Keyers also have 2 other parameters: the tolerance and the transition.

  • Tol: The tolerance allows you to make the Keyer more or less selective. By increasing this parameter, the range of selected colors will be the more important.

In the example below, we have chosen a low Tolerance: Tol = 5. The range of colors selected by the table is small.

Range of selected color when Tol=5

In the next example, we have chosen a higher Tolerance: Tol = 30. The range of colors selected by the table is higher. Here we have selected not only pure greens but also greens with traces of blue or red in them too.

Range of selected color when Tol=30
  • Tran: The transition allows you to make the Keyer more or less sensitive. By increasing this parameter, you will soften the borders between the selected colors and the deleted colors. This is very useful specifically if the video source is bad quality or if it has been compressed.

To modify these 2 parameters, use the 2 knobs to the left of and above the Trackball. The 1st knob allows you to modify the tolerance and the 2nd knob allows you to modify the transition. Also use the preview and the LCD screen to preview the result and control your parameters.

6. Inverse button :

The Inverse button allows you to reverse the color selection:

  • When the Inverse button is illuminated, the color selected is deleted and the other colors are saved.
  • When the Inverse is switched off, the selected color is saved and the other colors are deleted.

7. On Button:

Every Keyer is active in preview. To activate it on the MASTER output, press the On button until it lights up.

This function allows you to prepare and parameter each Keyer in preview without affecting the MASTER output.

Choosing the video source of a Keyer: In. Track:

What's more, the video source can be selected before (PreFx) or after (PostFx) applying the color effects:

  • By using the video source before the color effects, (PreFx) you can modify the colors of your video track without having to modify the extraction of your Alpha component.
  • By using the video source after the color effects (PostFx), you can modify the extraction of your Alpha component by modifying for example the RGB balance.

Use the In. Track button to select the video source of the Keyer.

In the example below, the In. Track input of the Keyer of track 4 is the track 3 PreFx:

R, G, B Mask:

The 3 keyer modes: R Mask, G Mask, B Mask allow you to extract one of the 3 Red, Green or Blue components (R, G or B) of the In.Track and to use it as a mask on the selected track.

The 3 components of the video are separated (Red Component, Green Component, Blue Component) and are used as masks.

Thus, in Red Mask mode, zones which contain red pixels (white zones of the mask) are made opaque while zones without red pixels (black zones of the mask) are made transparent. The same goes for the two other masks.