How to plan for a large projection system?
What does a large projection system consist of?
A large-scale projection system usually consists of following four parts: 1. input source, 2. video wall settings, 3. image geometric alignment with edge blending, and 4. projection.
The first thing that you need to be aware is that if you use PC based solution for video wall setting and image alignment, you will be limited to using only PC as the input source, making it difficult to use other input devices. On the other hand, if a non-PC solution is adopted for setting video wall and image alignment, then any digital devices can be used as input source – for example, media players, game consoles, cameras, and of course PCs. There are pro and cons for these two types of solution depending on the application. We are going to make further comparisons in this article, so you can evaluate which type is suitable for your project.
What is a video wall setting?
The video wall setting consists of two processes. The first is image crop, allowing you to crop image into portions and position it to projectors in assigned orders. The other process is to set overlap: in order to combine images seamlessly, some contents must be doubled at the edge between every two images, allowing them to be blended with no visible gap.
What is image geometric alignment and edge blending?
Due to various onsite installation factors, such as screen size, throw distance, or if you need to project images on an irregular surface, the geometry of projected images need to be adjusted. Sometimes, you might even need functions like ‘edge mask’ or ‘shift’ to eradicate redundant content. Edge blending is used to calibrate the color and brightness of the overlapped area between two images to make it look the same as the rest of the image.
What is PC solution and non-PC solution?
There are various solutions to achieve above mentioned processes, but they can be grouped into two main types: non-PC solution, or sometimes called stand-alone or solid-state solution; and PC solution or sometimes called media servers.
PC solution is a software application run on a PC. You use the software to control the image. The most critical thing that you need to be aware of is that there are usually high demands on PC hardware specifications in order to properly perform these complicated functionalities. For example, in order to action the overlap setting, the graphics cards must have the capability to properly crop and create overlap images- possibly not achievable using generic graphic cards and only with high-end ones, and they are usually much more expensive. Furthermore, multiple outputs graphic card (or multiple graphic cards) are needed in order to utilize multiple outputs to multiple projectors. The total cost of PC hardware plus software therefore might be quite high.
The non-PC solution is a solid state, stand alone, pure hardware solution. There can be two options for non-PC solutions. First, you can use a video wall controller to crop the image into multiple pieces then output them to multiple projectors. The projectors must have the functionalities of geometric alignment and edge blending. Another option is to use an all-in-one edge blending controller, sometimes called an edge-blending box. An edge blendeing controller facilitates all the processes, including video wall settings, geometric alignment and edge blending and some of them even come with advanced features, like multi-viewer or 3D projection mapping. The GeoBox edge blending box is the most typical non-PC solution.
Below we list a comparison between PC solutions and non-PC solutions:
| PC solution (Media server) | Non-PC solution (Hardware solution) | |
|---|---|---|
| External input source | Need capture card with fixed input resolution in some applications | Any input source without resolution limitation |
| Reliability | PC structure with more components, higher failure rate and potential compatibility issue. | Pure hardware and less component, so more reliable. |
| Image synchronization | Each projector needs one PC output, easy to have synchronization issue | Single source, no synchronization issue. |
| User flexibility | Content needs to be pre-rendered to fit the display setting, making it less flexible if user needs to replace contents regularly, for example, for retail shops or museums. | This solution only changes the way of displaying instead of altering the contents, so no content pre-rendering is needed. This makes it a perfect solution for users if contents need to be replaced often. |
| Video performance | CPU handles too many functions and resulting video lag and unstable | No PC CPU loading, better interactive and video performance |
| System setup | Calibration needs to be achieved through the software. Need experienced person for setup and calibration | Setup and calibration can be easily performed via IR remote controller, PC tool or WebGUI. |
| Geometric adjustment capability | Some high end software solutions can do more than 100 points in H&V direction. It is good for special applications, like dome projection. Some of them are built with auto-calibration. | 120x68 warp control points, which is sufficient for normal curve and warping projection. But without auto calibration capability, the installation might take longer time. |
| License, Virus, OS/software, upgrade and security | These are common PC issues. | no such issues. |
| High resolution display | Required PC spec with high end multiple output display cards. | Easy to achieve high resolution display through the input of single 8K/2K signal or cascading multiple 8k/2k resolution sources. sources. |
After comparing different ways of building large-scale projection systems, you might also want to know how to plan correct projector specifications for your system. In the article “How to display image using multiple projectors”, we will talk about this.
Our offerings
If you find non-PC solution better suits your requirement, we strongly recommend GeoBox products. GeoBox has a series of non-PC hardware boxes for using with large projection system. The high quality image processing technology (4K2K@60hz or 8K2K@30hz, RGB 4:4:4 color sampling, 10bits processor) is designed for professional AV applications. No special PC software is required: a truly robust solution. For more information, please visit our edge blending product page. More news and reference cases can be found on our LinkedIn page and Reference cases page.
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