Summary: They don't say. But the HDMI is 1.4a and the Current standard is HDMI 2.0, which was created to handle the features in 4K displays. So if you are buying this for 4K you are starting with problems that cannot be corrected. The advertised AirPlay really only works adequately with WiFi. This Machine does NOT have WiFI. You can buy a separate add on for $75.
Summary: I have yet to purchase this AV receiver but am looking closely at it. I give it three stars for this and the foregoing reasons. Page 26 of the user manual indicates that the two input component video sources (AV1-2), if they are other than 480i/576i signals, are output to the component video output only and not the HDMI output. I guess only 480i/576i component video signals are unconverted to HDMI.