Sometimes, a thin line, usually green but also yellow or black, may appear on the TV screen. This phenomenon is known as an overscan line. It occurs when the screen aspect ratio is set in modes such as “Screen Fit” or “Just Scan”. Although the names of these modes may vary from manufacturer to manufacturer, their goal is to display the entire image on the screen without cropping, so that all pixels are visible. An overscan line appears when the captured image has no information for specific pixels on the screen.
Causes of overscan lines and how to fix them
The overscan line appears for two main reasons. The first is that the received image does not contain information about all pixels. This happens when showing a video recorded from a broadcast, as not all channels transmit all video pixels. The second is a malfunction of the T-Con board that controls the display.
This problem is not critical and is often solved by turning on the 16:9 aspect ratio setting. With this setting, a small portion of the image may extend beyond the edges of the screen. This is especially noticeable when the laptop is connected to a TV, as some parts of the image may be cropped. However, this does not significantly affect the viewing of video on TV.
If the overscan line remains visible even after adjusting the aspect ratio, you can accept it as it is or consider replacing the display control board.
