Probably not the correct thread for these questions, but I don't see them asked anywhere else.
1. What 4K format will the TV need to accept?
4K/60 4:4:4 8-bit
4K/60 4:2:0 8-bit/10-bit
4K/30 4:4:4 or 4:2:0 8-bit/10-bit
4K/24 4:4:4 or 4:2:0 8-bit/10bit
I hope it is anything except 4K/60 4:4:4 as that is a 600 MHz bandwidth and HDMI cables are not good at supporting that over long runs to projectors.
2. Is HDMI 2.0 required? Or are HDMI 1.4 devices sufficient?
If HDMI 2.0, is HDCP 2.2 required?
3. Directv site mentions that 7.1 audio will be supported. I assume there is a single HDMI output on the C61K that carries both audio and video, and not a separate audio-only HDMI output like the Samsung UHD Blu-Ray player has. Based on the answer to my second question, I would need to know whether an HDMI 2.0 compliant AVR is needed to pass the HDMI through to the projector, or if an older HDMI 1.4 AVR is sufficient. I have a HDMI 2.0/ HDCP 2.2 compliant projector, but my AVR only supports HDMI 1.4 and is not able to pass though HDMI 2.0 video.
Does the C61K have an optical or coax SPDIF output for 5.1 sound?
EDIT: I found C61K specs at a retailer site that seems to answer most of my questions:
HDMI Output only
HDMI 2.0 and HDCP 2.2 required for 4K output
Digital Audio (Coax)
Optical Audio
So I would connect the C61K directly to my projector, and use the Digital Audio output to my AVR. It is likely that I would upgrade my AVR before we start seeing 7.1 audio anyway.
I just need to know what 4K format is utilized as I asked in question 1.
As I haven't been a Directv customer for the past 4 years, I don't want to start service again and have the install fail when confirming a 4K connection to my projector.