CEC is Consumer Electronics Control...
Panasonic Viera link
Every manufacturer has it...and it sucks.
CEC was "supposed to be" the way to connect an HDMI to the TV, then you could hide everything else(that was also included in the HDMI chain) in a closet, the next room...whatever. The problem is, CEC(as a "directive") has implementation holes in it large enough to drive a Mack truck through it.
CEC snafu's(just a couple)...
DVR's(from everybody) seldom have a "true powered down" state. Meaning if you turn on the "auto power" feature in your TV...it won't always respond, because of the DVR.
If your TV has the "auto power on" and you turn that on(which means the TV turns on when it senses a signal), and you turn on the sources(as in the BD player or receiver) "turn the TV on"...then the TV turns on, to then receive another code to turn right back off.
If the CEC is "sporadically" activated (meaning off in the TV, but ON in the BD player) then remote codes can be switched around. Meaning when you push play for the BD player, the BD player can receive the IR pulse from the front of its own panel, and receive it from the TV, cause the CEC is still active.(this one is mainly a problem on the few HDMI equipped DVD/BD players where play and pause are the same button)
And "out of the box", many TV/BD/AVR have their CEC turned on...so you actually have to go turn them off.