I’ve learned and am still learning some important lessons about HDMI cables as a school technology director. Unlike older VGA cables used with many classroom projectors in the past, HDMI cables can carry both video AND audio signals. VGA cables required the use of a separate (usally 1/8th inch) audio cable when playing videos or other multimedia with sound from a laptop computer or other computing device. The transition to HDMI-based classroom projection options is an ongoing journey for us at our school in our classrooms and meeting spaces. Here are a few of the lessons I’ve learned in the past year about HDMI connections.
Not all HDMI cables are created equal. We’ve had a couple HDMI cables in the past year just not work with newer classroom projectors we have ordered. (My preferred classroom projectors at this point, btw, are Casio “lamp free” LED models, which we’ve been able to purchase on Amazon for around $750 but also for as little as $530 each. If teachers want a TV instead of a projector, I’m a fan of Best Buy’s 55″ Insignia models since we can get them for about $320 each, but I suspect since prices are continuing to fall we’ll look for 65″ models down the road.) HDMI cables comply with different standards, ranging from 1.0 to 2.1, which was just finalized last month in November 2017. This comparison chart on the English WikiPedia page for HDMI cables is helpful to highlight the performance differences and capabilities. I have not attended to the HDMI cable specification ratings in the past as closely as I should have when ordering.
According to the December 2, 2017 LifeWire article, “High Definition Multimedia Interface (HDMI) Facts,” there are seven different HDMI product categories today:
- HDMI Standard
- HDMI Standard with Ethernet
- HDMI Standard Automotive
- HDMI High Speed
- HDMI High Speed with Ethernet
- Premium HDMI High Speed with Ethernet
- Ultra Premium HDMI High Speed (Forthcoming for 8K applications)
Sadly as I’ve been ordering HDMI cables in the past, I have not been aware of or attended to (as I should have) these HDMI cable category differences. HDMI.org has a helpful page, “Finding the Right Cable,” which elaborates on these HDMI product category characteristics and differences.
HDMI cables have distance limits which vary by their specification. HDMI extenders are available which can boost signal strength, but they can also degrade signal quality. Generally the recommendations I’ve read say you should limit HDMI connections to about 15 feet unless you boost the signal somehow. We haven’t done this in all cases at school, but we probably should according to “HDMI experts.”
A few weeks ago we connected two 65″ TVs on stands in our cafeteria with a DV camcorder connected to a HDMI splitter which duplicated the image on both TVs. We used the camcorder to provide a “live feed” of an elementary student choir performance for a packed audience of grandparents who didn’t all have a clear view of the stage from the back of the room. In getting this setup connected, I was both surprised and frustrated that a HDMI connection to a different camcorder did not work. I suspect (but was not able to confirm) that the video format, size, or HDMI specification being output by the camcorder did not match what our HDMI splitter could accept and use. Thankfully, we had a different HD camcorder which worked after being outfitted with a HDMI output adapter from Best Buy.
This evening for our winter orchestra concert, I connected one of our 65″ TVs on a rolling stand to that same HD camcorder which we put up in the sound booth, to provide a lobby-area overflow TV viewing option for people who could not fit into our auditorium. I tried using the same HDMI cable to connect the camcorder to the TV that I had used several weeks ago for our elementary choir performance “live feed,” but for some reason it wouldn’t work. I suspect it was because it was a 100′ HDMI cable, and that run was too long for the power of the HDMI signal from the camcorder. When I connected the same HDMI splitter box that I had used successfully with the same HD camcorder and TV, however, it still didn’t work. I ended up having to substitute a 25′ HDMI cable, and that worked directly between the camcorder and TV.
I’ve been relieved to get the HDMI camera feed to work for both of these events, but it’s NOT been an easy process to troubleshoot these connections. I need to learn more about HDMI cable differences and capabilities, and pay more attention (I’m guessing) to the required power and video format requirements of different devices before I order and/or connect HDMI cables.
I’ve learned all HDMI cables are NOT “created equal.” I’ve also learned it’s important to NOT assume a long run HDMI cable will “just work” the way you’d expect an ethernet cable run of 300 feet or less to always work reliably as long as the ends are crimped correctly. (Thankfully I don’t have to do ethernet cable crimping anymore. I used to dabble a bit in that, but no longer.)
What have you learned working with different kinds of HDMI cables in different situations? Do you have any insights or nuggets of wisdom to offer me? I very much want and need to learn more about this, even though I’ve had a steep learning curve the past few months with HDMI. If you have a comment or thought to share, please add it as a comment below on this post (the best option since others will also get to read/see our dialog) or reach out to me on Twitter @wfryer.
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- Podcast295: Reconsidering Paradigms of Value and Rewards for Teacher Expertise with John Costilla of WeAreTeachers.com - 2008
- Podcast208: Blending Learning with Powerful Ingredients - 2007
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