Ok All of you there is hope. So I took the time to read through mostly all the replies. A few things stood out. I had a chromecast connected to this TV last week with no issues other than I didn't like directing my TV from my phone as I do have guests come as well as younger kids that dont have phones. This is why Roku is king right now. It has a remote.
1.) Most all issues I read in this thread came from a Samsung TV (Not to say you won't find it on another model as you could be using a bad cable)
2.) It is quite apparent people did different things (To Fix) their issue but it all boils down to having your video display set to deliver the capability of the HDMI cable from the Roku to the TV. The simple fix may just be for Roku to supply the HDMI cable but hey who am I to say that..
3.) In my scenario I had the black and green screen in and out which green always signifies VIDEO and the black is a reset (Some would say of a Handshake) but in non-technical terms this is the ability to negotiate how fast can I talk and you still be able to comprehend what I am saying.. Having said that every device is going to try to talk the fastest they are able to from their end and renegotiate speed as often as they are programmed to do so.
4.) So I also have a Samsung with the SmartHub which is simply a box that has a bunch of HDMI ports and USB ports, and an optical port..etc... All these ports connect to the TV via one cable which by the way is not an end to end HDMI cable.
5.) So when I started my troubleshooting the configuration of my cables were the following. I had HDMI going out of the ROKU and into my Samsung Soundbar. A cable that ran HDMI out the Soundbar to the HDMI port 4 on the SmartHub and of course the Smart Hub ran to the TV.
I was to determine was it a defective Roku? Was it a Defective Cable? Was it that I was using a Smarthub? Was it that I was crossing over to the ROKU through my soundbar?
First I took a cable that went straight from the Smarthub to the Roku and changed it to HDMI Port1 on the Smarthub and the issue stopped. No Roku or Samsung TV settings were changed. So now I know it can be fixed without changing a setting but what was wrong? I then connected the cable I connected straight to the Roku from the Smarthub and plugged it into the soundbar HDMI in I took the Second HDMI cable plugged into HDMI Out of the soundbar and plugged it into the Roku.. (Problem now has come back.. Hmmm) So it is not the HDMI port 4 from the smarthub causing this as now I am still getting the issue plugged into HDMI port 1. It has to be something with my sound bar connection or the HDMI cable from the SOundbar to the ROKU as it is not the same exact cable brand I am using from the direct connection that worked. Next I tried to change out the HDMI cable from the Soundbar to the Roku. Now it is working without any issue again. The cable that ran from the Soundbar to the Roku that was causing these reset issues came with the soundbar originally but was not designed obviously for this video communication. So yes It was definitely the HDMI cable as I took one step further and did a direct connect from this HDMI cable from the Roku to the smarthub and the problem continued.
Bottomline you have to make sure your entire connection between your ROKU and TV all are transmitting at the same speed. The issue isn't a Roku or your TV it has something to do with both devices loosing sync with one another due to a piece of hardware in between both products HDMI ports. Now Im sure some have settings set to a hard setting. Keep everything set to auto and use the right cables and your problems will go away...
I've just recently upgraded to a Roku Ultra and I'm having the exact same issue. Everything works fine at 4K/30mhz, but trying to go to 60 results in flashing black screen...sometimes. I've switched cables. I'm now running directly from the Roku to the TV. I only have 1 port capable of running at 60mhz, so I can't try another port. Sometimes it works for a few hours, other times the stream is unwatchable.
I've checked the auto-detect settings, HDCP settings, display type settings. Nothing seems to help. Is there anything else I can try?
I have the exact same issue on a Sony receiver. Video flashes black. I swapped the Sony receiver out with a Denon AVRX3500H today and same issue. I am using a Sony projector instead of a TV. So far I set the Roku video to 1080p and the audio to Dolby Digital and the issue went away, at least for the last hour. Time will tell.
This is happening after upgrading to 9.2 on the ultra. I tried
a)" HDR subsampling menu under System > Advanced system settings > Advanced display settings and changed it from 4:2:0 to 4:2:2. Set the display mode back to 4K UHD 60Hz and so far it's been flicker free."
and b) switching cables.
It's connected to a converter for component but I had no issues before the update.
My Roku Ultra just did a Software Update yesterday to version 9.2.0 Build 4131-46. It's been blinking in and out ever since. I've turned Auto off for both the resolution and audio, but it's still regularly blinking out to black, and the back in again. Resolution is now fixed at 1080p and the Audio to PCM. When did Build 4131-46 first get pushed out? Is that the latest Build currently available for this box?