I am experiencing flickering when trying to set my display to 3440x1440.
In summary, I believe it is a HDCP issue or some statically configured expectation within the driver of how a HDMI 2.0 port should behave when communicating with it.
Below are the troubleshooting steps I have performed along with the hardware specs.
Intel NUC Hardware
OS: Win 10 Home x64
Memory: Single Kingston ValueRAM (Part Number: KVR21S15S8/4, 4GB Module, DDR4 2133MHz, Non-ECC, CL15, 1.2V, Unbuffered, SODIMM)
HDD: WD M.2 Blue 250GB (WDS250G1B0B, 250GB, SATA III, 6Gbs, M.2 2280)
Firmware and Drivers: The latest drivers and BIOS Update listed in the 'Drivers and Downloads' page for this product, have been installed for each component in the NUC, up to the date of this post (including the HDMI 2.0 Firmware Update).
Sony KDL-65X95000B (4K 60Hz TV, 4:2:0 8-bit, Not HDR compatible)
Sony KDL-46Z4500 (1080p 50Hz)
Hi-Speed cables 2K/4K V2.0 from EzyHD - https://www.ezyhd.com.au/
XBox One S provided HDMI cable
Thunderbolt to HDMI Adapter:
Moshi USB-C to HDMI Adapter - https://www.moshi.com/usb-c-to-hdmi-adapter
NOTE: I understand the compatibility only states MAC products, but it works, and exhibits the same behaviour as the HDMI port, however I'm not really concerned with this (it's HDMI that concerns me)
OS: Win 10 Pro x64
Graphics Card: NVidia GTX 1080 TI
Monitor: Acer X34 Predator (DisplayPort 1.2a, HDMI 1.4)
1) My desktop PC has NO issues displaying the TV at 3440x1440 resolution - No flickering
2) My XBox One S has NO issues detecting the TV as 4K capable, and has no issues displaying the TV at 3440x1440 resolution
3) My FetchTV box has NO issues detecting the TV as 4K capable, and has no issues displaying the TV at 3440x1440 resolution
4) My Surface Pro 2 has NO issues displaying the TV at 3440x1440 resolution - No flickering
5) The NUC shows that the recommended display settings for the TV is 1920x1080 (even though it is a 4K TV). I have no flickering at this resolution.
6) As soon as I set the Display settings to 3440x1440, I get the message saying that this is not the recommended display settings for this device, and I begin to get flickering. It is stable at 1920x1080.
7) I have also tried various refresh rates, 30Hz, 59Hz, 60Hz etc....but still get flickering.
8) Various power cycle methods on the TV and NUC including - Rebooting, Sleep, Shutdown, Removing power sources, changing inputs, powering up the devices in specific sequences etc..., sometimes provide stability at the 3440x1440 resolution (I have more stability using the Thunderbolt to HDMI Adapter), however even when its stable, i can verify its still not working poperly when trying to watch 'Foxtel Go', where I get no picture (see further down regarding Foxtel Go)
9) All HDMI ports on the TV have been tried
10) CEC has been tried ON and OFF on the TV
11) All display and sound modes have been tried on the TV
12) I have tried the TV's supplied HDMI splitter which produces the same reults
13) When using other HDMI inputs that aren't HDMI input number 1, it sometimes switches the TV's inputs to HDMI 1 (may have been more prominent before I disabled CEC)
1) I cannot watch any channels in Foxtel Go when using it through the Sony KDL-65X95000B using HDMI at 1920x1080 resolution (Thunderbolt to HDMI Adapter doesn't work either, however this is expected behaviour so it's not a consideration)
2) I have tried all of Foxtel Go's troubleshooting steps for this particular issue, however I have verified it is not an application issue - see the next 2 points
3) When I plug the NUC in to my Desktop PC monitor, Foxtel Go works
4) When I cast my desktop on the NUC to a chromecast, which is also connected to my Sony KDL-65X95000B TV, I cannot watch any channels. However, as soon as I unplug the HDMI connection from my NUC to the TV, and still casting to the chromecast, I can watch channels
5) Its clear that there is an issue with the HDMI 2.0 here
1) When using HDMI, I just get a black screen - doesn't work at all at 1920x1080
2) When using the Thunderbolt to HDMI Adapter, it works at 1920x1080 (Foxtel Go doesn't work as expected as we are using the Thunderbolt to HDMI Adapter).