Originally Posted by Lee Stewart
What are HDMI InfoFrames
That is a data block, sent by the player to indicate the 3D format of the current video signal. This did not exist before HDMI 1.4, and does not have to be sent for 2D signals. The TV uses this to automatically enable the 3D presentation of a 3D signal.
It is defined in section 8.2.3, "HDMI Vendor Specific InfoFrame" of the HDMI 1.4a spec (in the publicly available 3D extraction as well)
Before this, only the "AVI InfoFrame", defined by the CEA 861 spec, was used to convey the meta data of the video signal. Since CEA and HDMI are different organisations, HDMI could not add the 3D tagging to the AVI InfoFrames. So, they created their own custom InfoFrame and are sending that alongside the AVI.
It will also be used for the 4K video modes, which as well are specified by HDMI and not by CEA.