6 HDMI

You should know the following terms:

• HDMI (High-Definition Multimedia Interface)
• TMDS (transition-minimized differential signaling)

How HDMI works

HDMI works by the use of transition-minimized differential signaling (TMDS) technology to transfer information or data from one location to another. It’s a method for transmitting high-speed digital data.  It prevents degradation of this data as it travels through the cable from one device to the other. 

TDMS is a technique that protects information from degradation as it travels down the cable length from one device to another giving the user high-quality audio and video images. It also has the capability to protect data from piracy through HDCP (high-bandwidth digital protection.)

Troubleshooting HDMI

The first step in troubleshooting an HDMI issue is checking the cables on both ends to be sure they are plugged in correctly. Check for damage to the pins and be sure the cable is not frayed or damaged in any way. Disconnect and connect the cables on both ends to be sure they are properly seated. Don't forget to check the wallplate as well. 

Check to be sure you are using the correct input on the device. A remote control cycles through all of the inputs when Input is selected. If there are multiple HDMI inputs, try a different one to see if that resolves the issue. If the display’s resolution is set to AUTO, consider resetting it to match the resolution of the device you are connecting to. Lowering the resolution or refresh rate can sometimes help. In some cases, firmware or driver updates may be necessary for any of the equipment you are using.

Image Credit: https://www.sony.com/articleimage/servlet/servlet.FileDownload?file=0155F000006bu6uQAA

If you are using the correct input on the device, try using a cable that you know works to see if that resolves the issue. The other cable might be malfunctioning or it could be an older cable that doesn't work with the device. There are different versions of HDMI cables (1.4, 2.0, and 2.1) and some newer devices may need a 2.0 cable which can transmit 4K at 60Hz to support higher frame rates, 32 audio channels, and two simultaneous video streams. The older 1.4 cable can transmit 4k but is limited to 30Hz and 8 audio channels. Check your displays refresh rate to see if it is 30Hz or 60Hz and your cable can support it.  

Also consider the length of your cable. If you are using an especially long cable, see if a shorter one might work. If not, an HDMI signal booster or extender might be necessary to improve the signal over the cable.

You may need to perform a reset of the HDMI device. Steps to perform a simple reset include:

1. Turn off the connected device and the TV.

2. Unplug the power cords of the device and the TV.

3. Allow both the device connected and the TV to remain without power for about 30 seconds.

4. Plug the power cords of the device and the TV back into the electrical outlet.

5. Turn on the connected device and TV.

If you plug in a cable and get a signal for a second and then it drops, it could be a hardware issue. If the equipment is older, it may not have the correct handshake. Consider trying a different computing device to see if it's a computer issue. Also consider making sure the connected device is configured to output through its HDMI Connection and that the TV or monitor is compatible. Replacing the cable isn't the solution if the equipment on either end is older and doesn't have the proper handshake. 

Information Credit: Sony's Troubleshooting HDMI Guide  

Complete the following task or self-assessment:

Do a survey of your classrooms to see how teachers are connecting to Video.

•  Are they using VGA or HDMI? 
• Do they have to use adapters to connect? 

Use the data you collect as a means to help your supervisor or principal(s) understand why the school’s equipment should be updated.