# Lightning Bezel compensation

## Lightning Bezel compensation

When using video walls, the monitor’s bezel gaps can introduce space that was not intended to be there resulting in a disjointed image that is not continuous across all displays. Using bezel compensation produces a more continuous image across the displays and provides a more realistic experience. It is like looking through a multi panel window where the window frames block your view. So we need to remove the video that would be hidden by the frames or in this case bezels. Below is an example of a 2×2 video wall with and without bezel compensation applied.

without bezel compensation

with bezel compensation

Bezel compensation can be calculated in a few different ways. If the display has a uniform bezel size then calculations can be simply performed. Calculations become a little more complex when the bezel sizes are not the same. For instance, some displays will have a larger bottom bezel than the top, or the sides can vary from each other.
Bezel compensation only applies to edges of the video potions joining to another display. Only the orange edges of the below examples need to be compensated.

Definition of terms:
SRW = source video resolution width in pixels
SRH = source video resolution height in pixels
DR = number of physical displays in the row (side-by-side)
DC = number of physical displays in the column (top-to-bottom)
BW = physical width of the display bezel in millimeters (when using uniform bezel size)
B = bezel size in pixels (when using uniform bezel size)
BWL = physical width of the displays left bezel in millimeters (when using different bezel sizes)
BWR = physical width of the displays right bezel in millimeters (when using different bezel sizes)
BWT = physical width of the displays top bezel in millimeters (when using different bezel sizes)
BWB = physical width of the displays bottom bezel in millimeters (when using different bezel sizes)
BL = left bezel size in pixels (when using different bezel sizes)
BR = right bezel size in pixels (when using different bezel sizes)
BT = top bezel size in pixels (when using different bezel sizes)
BB = bottom bezel size in pixels (when using different bezel sizes)
OW = physical overall width of the display in millimeters
VW = physical width of the displays viewable area in millimeters
OH = physical overall height of the display in millimeters
VH = physical height of the displays viewable area in millimeters

We are going to look at an example of a uniform bezel sized display, and one that is not.
1) Uniform bezel size
For a 2×2 video wall with uniform bezels we are going to use the following values:
• SRW = source video resolution width in pixels
• DR = number of physical displays in the row (side-by-side)
• OW = physical overall width of the display in millimeters
• VW = physical width of the displays viewable area in millimeters

Firstly we need to know a few dimensions of the display in millimeters.
• physical width of the display bezel in millimeters (BW)
• physical overall width of the display in millimeters (OW)
• physical width of the displays viewable area in millimeters (VW)
BW can be physically measured, or calculated from OW and VW like below:
((OW – VW) / 2) = ((615 – 595) / 2) = 10
Now we need to know how many displays we have in rows and columns.
A 2×2 wall has 2 rows and 2 columns.
So DH = 2 and DV = 2

The last detail we need to know is the source resolution in pixels.
This example uses 1920×1080 so SRW = 1920
Now we have all the information we require, we can use the formula below to calculate the bezel compensation required in pixels.
B = (((SRW / DH) * BW) / VW) =
(((1920 / 2) * 10) / 595) =
(((960) * 10) / 595) =
((9600 / 595) =
16px

width = ((SRW / DR) – B)
height = ((SRH / DC) – B)
h_offset = ((SRW / DR) + B)
v_offset = ((SRH / DC) + B)

2) Different bezel sizes
For a 2×2 video wall with different bezels we are going to use the following values:
• SRW = source video resolution width in pixels
• SRH = source video resolution height in pixels
• DR = number of physical displays in the row (side-by-side)
• DC = number of physical displays in the column (top-to-bottom)
• OW = physical overall width of the display in millimeters
• VW = physical width of the displays viewable area in millimeters
• BWx = bezel width in millimeters

Firstly we need to know a few dimensions of the display in millimeters.
• physical width of the display left bezel in millimeters (BWL)
• physical width of the display right bezel in millimeters (BWR)
• physical width of the display top bezel in millimeters (BWT)
• physical width of the display bottom bezel in millimeters (BWB)
• physical overall width of the display in millimeters (OW)
• physical width of the displays viewable area in millimeters (VW)
• physical overall height of the display in millimeters (OH)
• physical height of the displays viewable area in millimeters (VH)

Now the bezel on each side of the display need to be physically measured.
BWL = 10mm
BWR = 10mm
BWT= 10mm
BWB = 20mm
Now we need to know how many displays we have in rows and columns.
A 2×2 wall has 2 rows and 2 columns.
So DR = 2 and DC = 2

The last detail we need to know is the source resolution in pixels.
This example uses 1920×1080 so SRW = 1920 and SRH = 1080
Now we have all the information we require, we can use the formulas below to calculate the bezel compensation required in pixels.
Left bezel compensation =
BL = (((SRW / DR) * BWL) / VW) =
(((1920 / 2) * 10) / 595) =
(((960) * 10) / 595) =
((9600 / 595) =
16px

Right bezel compensation =
BR = (((SRW / DR) * BWR) / VW) =
(((1920 / 2) * 10) / 595) =
(((960) * 10) / 595) =
((9600 / 595) =
16px

Top bezel compensation =
BT = (((SRH / DC) * BWT) / VH) =
(((1080 / 2) * 10) / 335) =
(((540) * 10) / 335) =
((5400 / 335) =
16px

Bottom bezel compensation =
BB = (((SRH / DC) * BWB) / VH) =
(((1080 / 2) * 20) / 335) =
(((540) * 20) / 335) =
((10800 / 335) =
32px

width = ((SRW / DR) – (BL + BR))
height = ((SRH / DC) – (BL + BR))
h_offset = ((SRW / DR) + BL)
v_offset = ((SRH / DC) + BT) 