Answer: D. When the display effect of the display is not ideal
Answer analysis:
When discussing this issue, we must first clarify the functions and roles of LED display screens and video processors.
LED display screens are mainly used to display various images, texts and video content, while video processors are used to convert, enhance, adjust and process the input video signals to ensure that the image quality displayed on the LED display screen is the best.
Now, let's analyze the options one by one:
A. In any case:
This option is too absolute. Although the video processor is very helpful in improving the display effect of the LED display screen, it is not necessary to use it in all cases. For example, when displaying simple static images or text, the complex processing function of the video processor may not be required.
B. When the display screen displays different pictures:
This option only points out the changes in the display content of the display screen, but does not involve why the video processor is needed. Displaying different pictures does not directly mean that a video processor is needed unless there are special requirements for the conversion or display of these pictures.
C. When the display screen needs to switch to display different pictures:
Although this option also involves picture switching, it more points out a functional requirement of the display screen, that is, the ability to flexibly switch and display different content. However, this does not directly explain why a video processor is needed. Screen switching can be achieved in many ways, including but not limited to video processors.
D. When the display effect of the display screen is not ideal:
This option directly points out the problem of the display effect of the display screen.
When the display effect of the LED display screen is not ideal, it is likely that the input video signal does not match the physical characteristics of the display screen, or there is a quality problem with the signal itself.
At this time, it is particularly important to use a video processor to process and optimize the signal.
The video processor can adjust the brightness, contrast, color and other parameters of the signal to ensure the best image quality finally displayed on the LED display screen.
In summary, when the display effect of the LED display screen is not ideal, using a video processor is an effective solution. Therefore, the correct answer is D: "When the display effect of the display screen is not ideal".