How does a HDMI handshake work?

Trevor

Registered
Thread Starter
Joined
Dec 13, 2020
Messages
4
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.
 

tripplej

AV Addict
Joined
Jul 13, 2017
Messages
5,922
My AV System  
Preamp, Processor or Receiver
NAD T-777
Universal / Blu-ray / CD Player
Oppo 103 Blu Ray Player
Front Speakers
7 Paradigm Reference series 8" in ceiling speakers
Subwoofers
2 Paradigm SE Subs
Other Speakers or Equipment
Nintendo Wii U Gaming Console
Video Display Device
Samsung UN75F8000 LED TV
Remote Control
Universal Remote MX-450
Streaming Subscriptions
Sony PS4 Gaming Console, Panamax MR-5100 Surge

Trevor

Registered
Thread Starter
Joined
Dec 13, 2020
Messages
4
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?
 

gp4Jesus

New Member
Joined
Feb 27, 2022
Messages
13
My AV System  
Preamp, Processor or Receiver
Outlaw Audio 976
Main Amp
Several Rotel RB-981s
Additional Amp
2 Rotel RB-980BX
Universal / Blu-ray / CD Player
Samsung 5900 BDP; Phillips CD changer
Front Speakers
Polk Audio RTi A7
Center Channel Speaker
CSi A6
Surround Speakers
RTi A3
Subwoofers
4 Audio Pro Subs; LFE Sunfire True Signature
Video Display Device
Samsung 60” LED
Remote Control
Harmony
Streaming Equipment
Fire stick
Streaming Subscriptions
Many
Satellite System
Dish
Other Equipment
4 EXOs
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
 

thothsong

Member
Joined
Jun 29, 2021
Messages
130
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.
 
Top Bottom