维奥

1. Introduction

For super-high-resolution LED driving, we often use video scaler (such as VDWALL LVP605 LVP615) or video splicers (such as VDWLL LVP919, LVP909，A6000) for mosaic display. This article shall help users understand the principle of manual mosaic calculation.

2. Splicing principle

The function of video processor is to access various video signals and scale the input signal to the resolution of the corresponding LED screen as required. Similarly, splicing also scale up cropped image to required resolution accordingly. It just means that since the screen total resolution exceeds one single DVI output loading capacity, so we use multiple DVI outputs jointly drive the screen. In splicing solution, the function of each DVI output is to crop associated input image and scale it up to unit screen resolution. To guarantee splicing effect, each DVI output should scale image under same aspect ratio. This is fundamental principle for video splicing.

3. Manual Mosaic parameters calculation method

The splice parameters include:

The first four items are output parameters. The output width and height of each DVI output should correspond to unit screen physical resolution driven by each DVI output . The output H(horizontal) start and V(vertical) start are generally set to 0 by default. The last four items are the input image parameters we need to calculate.

Next, we will explain how to calculate the splicing parameters with a practical case.

① Screen manual mosaic with same pixel pitch

As shown in the figure above, we use LVP404 to drive this P5v LED display with a resolution of 3360*2016. We set the output resolution of LVP404 to 1920*1080 and divide the LED display into 4 displays.

LVP404 is equipped with 1 input board and 2 output board utmost. The function of the input board is to switch the input signal and scale it to output resolution. When the output board detects the input image and scales it up, it is based on the output resolution. Therefore, when we calculate the scaling ratio, not based on input signal (such as source input resolution 1600x1200), but the output resolution of LVP404.

Horizontal input image cropping ratio= total output width / total input width = unit screen output width / unit screen input width.

Vertical input image cropping ratio = total output height / total input height = unit screen output height / unit screen input height

Accordingly:

Horizontal image cropping ratio=3360/1920=1728/OUT1 input width=1632/OUT2 input width

As calculated: OUT1 input width=1728x1920/3360=987, OUT2 input width=1632x1920/3360=933.

So forth, the input height, input horizontal start and input vertical start can be calculated, as the following table:

② Screen manual mosaic with different pixel pitch

Screens with different pixel pitch manual mosaic calculation is not based on pixels but screen physical dimension, so as to keep same aspect ratio avoid image deformation. As following formula:

so：

otal screen width (unit MM) / total input width pixels = unit screen width (unit MM) / unit screen input width pixels

Total screen height (unit MM) / total input height pixels = unit screen height (unit MM) / unit screen input height pixels

For example, for the above 3360*2016 P5 display screen, the 1632x2016 part on the right side is changed to a P6 screen with same display square, then the resolution of this part of the P6 display screen is calculated to be 1360x1680.

Then our calculation procedure is:

(1728x5+1360x6)/1920=(1728x5)/OUT1 input width=(1360x6)/OUT2 input width.

So: OUT1 input width=(1728x 5) x 1920/(1728x 5+1360x 6)=987, OUT2 input width=1360x 6x 1920/(1728x 5+1360x 6)=933.

In the same way, the input height, input horizontal start and input vertical start can be calculated as the following table.

③ Irregular screen with different heights

In actual stage applications and other occasions, for irregular screen manual mosaic calculation, for the same aspect ratio, we must count in the devoid area’s pixel. Calculated As below:

The main screen in the middle is 5 meters wide and 3 meters high, and the two lateral screens are 1 meter wide and 4 meters high. When we calculate, the total LED total width should be considered as 7 meters wide and 4 meters high, because the height of middle screen is 3 meters, we need to set starting point as 1 meter, achieve consistent display without different aspect ratio.