HDMI-CEC Guide: What it is and why you should have it (and use it)

HDMI-CEC works by sending messages, either in broadcast mode or on addressed mode. These messages mimic user actions through the remote, and is intended to use the TV remote as the single remote to rule all other devices connected to it. For this to happen, a number of features where defined, from which the following are the most relevant:

  • One Touch Play – This is the baseline CEC functionality. This features defines that whenever a source device is turned on and ready to output content, the TV shall turn itself on, if required, and select the correct HDMI input so that the content coming from the source is displayed on the TV.¬†
  • Routing Control – This feature is complementary with One Touch Play as it implements the same kind of functionality as the One Touch Play, but applicable to HDMI switches (including the HDMI switch functionality on AV receivers). This use case renders any HDMI switch remote supporting CEC useless¬†(but not the AV receiver remote).
  • System Audio Control – This feature has one single goal: render the AV receiver remote useless, by taking control of the audio volume control for the whole HDMI tree. The need for this specific use case is due to the particulars of it: although most HDMI use cases are a two part affair, when using an AV receiver, it gets a three way. Video and audio are sent from the source device, but the TV only displays video. Audio is consumed at the AV receiver and the TV shall mute it’s own speakers.
  • Remote control pass through – This is exactly what it seems, with one fundamental remark: it is designed to be used with the TV remote. As the whole CEC architecture, the root device is the TV, and as such, the master remote is the TV remote. The whole point of this, is for the TV to forward any generic remote key press (such as Ch+, a channel number or the menu key) to the active CEC device. The is also the most important CEC use case, and with the other remaining use cases, renders all remotes useless but the TV remote.
  • System Standby – This is the final use case, and is extremely simple: if the TV is turned off, so shall be all devices on the HDMI chain, final.

Now, a number of use cases which before would seem cumbersome and complicated for users are now simple, quick as easy, by using one simple remote. Let’s then try to summarise the AV experience before and after CEC.

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