How does a HDMI handshake work?

Trevor

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I have a question about HDMI that I can’t post in the Tech Talk forum as I don’t have the privileges.

I am trying to resolve an HDMI issue between my Mac Mini and my LG TV, which I use as a second display. The interface between the two works fine if I use a USB-C port and an HDMI adapter.

However, when I use the HDMI port on the computer it does not recognize the TV consistently. I have tried talking to Apple support, but they blame the TV. There are many others out there with the same issue on many other different TVs.

Before I get into any specifics, could someone direct me to somewhere that I could learn how the HDMI handshake works? I would like to understand more before I start asking detailed questions.
 
Hi trippleJ,

Thank you for your reply, I have read the links you listed. That one particular TV setting did not resolve it for me.

I do not have a consistent set of symptoms to give you, but the TV is intermittently recognized through the HDMI port whereas the TV is always recognized through the USB-C port (with HDMI adapter).

My gut feeling is that the HDMI handshake between the two fails, and is not reattempted. I believe it is supposed to keep trying, and maybe it is but I don't know how to tell. How often should the handshake be occuring, and which unit sends the invitation to communicate; the computer or the TV?
 
Thanks for starting this thread.

I’m trying to hack a manual “single HDMI in double HDMI output” switch, so on power up, my pre/pro trigger will switch for me. It’s complicated, too complicated to explain right now.

Tony
 
The HDCP protocol is initiated by the source device. In case of failure, the source "must retry periodically, with a period of no more than 2 seconds (preferably much more often)". You can read the HDCP 2.3 specification if you want full details.
 
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