A 40-meter HDMI cable is quite long for standard HDMI use, and it is important to ensure that the quality of the cable and the signal transmission are sufficient over such a distance. Here are a few things to consider when purchasing or using a 40-meter HDMI cable:

1. Signal Loss and Quality:

• Standard HDMI cables may experience signal degradation over long distances, especially for resolutions above 1080p or for high-bandwidth features like 4K or HDR.
• For a 40-meter cable, active HDMI cables (which amplify the signal) or fiber-optic HDMI cables are ideal, as they help reduce signal loss compared to passive copper HDMI cables.

2. Resolution and Bandwidth:

• If you are using 4K resolution or higher, make sure the cable supports the necessary bandwidth. For instance, cables designed for HDMI 2.0 or HDMI 2.1 are required for 4K at 60Hz or 120Hz (with higher bandwidth).
• For 1080p or lower resolutions, a regular HDMI cable may work fine, but for 4K or higher, you'll need a high-quality cable with support for higher speeds (like 18Gbps or 48Gbps).