Optimizing Bezel Settings
The bezel is the physical frame surrounding the active area of a display. When configuring a wall, bezel compensation must be used in order to correctly display the image across the video wall. When bezel compensation is not used, the segments of the image can seem to be visually disjointed and the overall effectiveness of the video wall will be diminished. By using the appropriate bezel compensation settings, the image will appear more unified and the appearance of the video wall will be enhanced.
 Diagram of 2x2 Wall Configuration without Bezel Compensation |  Diagram of 2x2 Wall Configuration with Bezel Compensation Applied |
Bezel compensation subtracts horizontal or vertical lines of video from the edges between the displays in order to decrease the appearance of separation between the segments of the image. The bezel compensation values specifically refer to the number of lines to omit for the top, bottom, left, and right bezels. It is assumed that all of the displays used in a wall have the same bezel dimensions.
As bezel compensation is adjusted by omitting lines of the video signal, the total physical amount of bezel compensation per adjusted value is dependent on the source resolution as well as the physical size of the display. For example, on a 55-inch 1080p panel, each line of the video signal is approximately .635mm wide. However, if that panel were 720p, each line is approximately .952mm wide. For this reason, the bezel compensation values must be adjusted for different display resolutions, as each resolution has a different line width for a given display size. To make this easier when working with content with varying resolutions, a unique video wall configuration should be created for each resolution for a given video wall.
The displays used in a wall should be identical. Displays from different manufacturers or even different models from the same manufacturer will have different bezel sizes, input lag, and color reproduction.
Determining Bezel Compensation Values Visually
There are two ways to determine the values to use for these fields. The first method is to do a visual inspection using a static graphic spanning the wall. First, assemble and configure the video wall, with bezel compensation values set to 0. After saving the configuration, go to the Routing Tab and assign the source with the test graphic to the newly created wall destination. Look at the video wall and take note of any inconsistencies in the appearance of the test graphic from monitor to monitor. In particular, angled lines that cross between bezels will not be aligned if the bezel compensation settings are incorrect.
Diagram of 2x2 Wall Configuration without Bezel Compensation
Next, return to the wall configuration in the Wall Setup tab. Adjust the bezel compensation values and then save the wall. Note that changes made to video wall configurations will not immediately take effect; the source must be re-joined to the wall. To view the changes made, navigate to the video routing tab and join the source device to the video wall destination again. If the image still appears to be incorrect, repeat the process, checking the test graphic after each bezel adjustment.
Diagram of 2x2 Wall Configuration with Bezel Compensation Applied
Determining Bezel Compensation Values Mathematically
There is also an approach to calculate the correct bezel settings. The first step of this approach is to determine the pixels per inch (PPI) of the displays.
To do this, measure the width of the active display area in inches, not including the bezel. Next, divide the horizontal resolution by the width of the display area. The resulting value is the PPI of the display. Next, measure the top, bottom, left, and right bezel dimensions in inches. Multiply each of those values by the PPI. Then divide the results for top and bottom by the number of wall rows. Divide the results for left and right by the number of wall columns. Round all the results to the nearest whole numbers. Enter the resulting whole numbers into each of the bezel fields.
The calculated values will be approximate and may require slight adjustment to achieve optimal results.
Given a 4x60" 1920x1080 Displays in a 2x2 Wall Configuration:
Inputs
- Display area width: 52.5"
- Horizontal resolution: 1920
- Top Bezel width: 1.0"
- Bottom Bezel width: 2.0"
- Left Bezel width: 1.5"
- Right Bezel width: 1.5"
Calculated outputs
- PPI = 1920/52.5 = 33.6
- Bezel Top = 33.6 * 1.0 / 2 = 16.8
(Round to 17 pixels and enter into top field) - Bezel Bottom = 33.6 * 2.0 / 2 = 33.6
(Round to 34 pixels and enter into bottom field) - Bezel Left = 33.6 * 1.5 / 2 = 25.2
(Round to 25 pixels and enter into left field) - Bezel Right = 33.6 * 1.5 / 2 = 25.2
(Round to 25 pixels and enter into right field)