[mythtv-users] HDMI-CEC ?

Simon Hobson linux at thehobsons.co.uk
Tue Oct 11 18:20:55 UTC 2011

tortise wrote:

>While, CEC to me is a good concept, it seems to require an HDMI chain.

That's rather inplicit in the whole idea !

>(Although CEC commands may also be routable over Ethernet?)
>An IP solution seems a better way to go as it is even more widespread
>than HDMI

Actually I disagree. IP is VERY new in this context and HDMI is far 
more ubiquitous. The other thing is that HDMI by definition connects 
the devices you want to control, and almost certainly does not 
connect devices you don't want to (eg other disk players, tvs, etc in 
the house).

As to nVidia and support for CEC, looking on Wikipedia I see that CEC 
is carried on it's own pin. Thus it doesn't need support from the 
video chip at all, it just needs that pin either bringing out to a 
header for something external to be connected, or it needs connecting 
to a suitable (and separate) comms chip to send/receive messages.
Of course, the video chip manufacturer could include this in the 
video chip - but it's not mandatory.

CEC being on a separate pin is quite convenient for the manufacturers 
of the unit that started this thread - it means they don't have to 
have any circuitry to deal with the high speed video signals, and can 
just link teh pins across from one HDMI connector to the other.
Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
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