@timfolk can you try playing a couple different 4k HDR sample(maybe from https://4kmedia.org/) to see if you get the same results.
Yep - 2160p50 and 2160p59.94 HDR may well push your HDMI cable to higher clock speeds than 2160p23.97/24 content which will run at lower bandwidth particularly if you are using 4:2:2 not 4:2:0 at 2160p50/59.94
I tried the next files from the site you suggested:
LG Cymatic Jazz HDR10 4K Demo.mp4
Life Untouched 4K Demo.mp4
Sony Swordsmith HDR UHD 4K Demo.mp4
Samsung Travel With My Pet HDR UHD 4K Demo.ts
Samsung Wonderland Two HDR UHD 4K Demo.ts
Other than Samsung Wonderland Two HDR UHD 4K Demo.ts which played perfectly, the others gave me a black screen, the HDR logo didn’t even pop up and after a few seconds the TV reported no signal.
That almost certainly suggests you have a dodgy HDMI cable.
If it’s just that, I’m happy 
the cable I use is supposed to be good and overqualified, but I’ll get another and try.
I’m curious to hear if the dispinfo indicated anything.
Thanks for all the replies.
I went and got a certified premium high speed hdmi from the same brand (Club3D). Believe it not, it’s the only one I can find in a local shop. This has the same symptoms and somewhat worse. Sometimes I get 4K picture and sometimes not, when I do it has white sparks all over it and extreme audio distortion.
The one clip that worked before ( Samsung Wonderland Two HDR UHD 4K Demo.ts), doesn’t work now either.
I tried also the whitelist thing from recommended kodi settings. The N2 CE Edition came with all the 4K resolutions enabled, I made sure the 4096x isn’t, also tried to disable all the enabled resolutions like the guide suggests. It didn’t make any difference.
The odd thing is that the Ultra High Speed cable did work fine since the day I got the N2 till I tried that test file.
I guess next step is to order a monoprice cable and hope for the best. Sadly, this can take a few weeks to arrive.
Did the logs show anything useful?
I have not heard anything bad about Club3D cables, if you got a different cable and still have the same problem, I don’t really know what else to suggest.
All the symptoms you are describing mean bad cable or a lot of interference. Do you have an AVR or is it a direct connection from the N2 to the TV? Also what is the length of the cable you are using?
N2 connected directly to tv, HDMI is 3m/10ft long.
The harsh sound comes from the tv speakers it seems, though they are not even set to play sound (audio is set to go through my old analog receiver).
Do you have a HDMI 2.0 cable which is shorter than 1m/3ft to test? The length could be problematic, however, given the Club3D 3m/10ft cable is certified, it should be okay I guess… At least return the Club3D cable and look for another option like the monoprice. Is it possible to move the N2 closer to your TV so you don’t have to use a 3m/10ft cable?
I ordered monoprice cables from amazon but it would take a couple of weeks to arrive. They are 3m too though.
The shop only has 1m or 3m Club3D cables, 1m is too short :s I guess for testing purposes I can get one of those.
White sparks = failing HDMI connection
That suggests a hardware issue - either your HDMI cables are not capable of carrying the bandwidth of video that is being sent, or are too long, or aren’t fully connected - it’s amazing how a cable not fully pushed into a socket can be ‘marginal’.
It is remotely possible that there is a hardware fault - but it’s not the most obvious first cause.
I disconnected and reconnected the cable so many times by now that not fully connected doesn’t seem possible. Length: I thought 3m isn’t that long but I’d try replacing it to a 1m one and try, it is a bit too short though but worth trying I guess. Maybe the monoprice ones will be a revelation but need to wait on those.
The whole thing about HDMI cables is a weird one as all of my cables are ancient, at least 10 years old and I have no issues playing anything it seems.
Yep - no reason why a 10 year old cable won’t work at 2160p60 4:2:2 12-bit if electrically it’s capable of carrying that signal. It’s basic physics.
That doesn’t mean all 10 year old cables will - and those that were value engineered to ‘just about work’ at the lower bandwidth modes used by HDMI 1.4b and below are unlikely to work reliably at the higher bandwidth modes introduced by HDMI 2.0.
NB - there is one 2160p50/60 mode on HDMI 2.0 that is low bandwidth and was introduced to the spec to allow HDMI 1.4b hardware to carry 2160p50/60 content - which is the 4:2:0 mode.
I’ve always suspected that like you say, the quality of cable is important but as long as all pins are wired then why wouldn’t an older cable work. The version on the socket is way more important obviously.
It’s not just having the pins wired that’s important.
HDMI signals are very high data rate - Gigabits per second. This means that the inherent low-pass filtering caused by the internal resistance and capacitance of a cable has a major impact on performance. If your cable can’t carry higher frequencies (because of the inherent filtering) then higher bandwidth HDMI signals will cease to be reliably decoded by HDMI receiver hardware. The thinner the cable of each HDMI pin-to-pin connection, and the longer the cable, the higher the resistance will be, and the lower the cut-off frequency of the low-pass filter that is naturally created in the cable. This means that higher bandwidth HDMI modes won’t successfully pass.
The same with poor connections at each end. If you have an almost-but-not-quite fully connected HDMI connector - you will get a higher-than-normal resistance connection (say where only a small percent of the connectors actually touch each other) This will also cause filtering - and higher frequency HDMI modes to fall off the digital cliff.
Everything else being equal (which it obviously isn’t) - thicker cables (i.e. those with thicker conductors) may perform better than thinner cables. (I’m not saying all thick cables are better than all thin cables - and certainly don’t pay over-the-odds for ‘HiFi Grade’ HDMI cables - just basically electrically capable is all you need)
Again - basic physics.
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Got a 1m/3ft cable today from same brand (quick recap: local selection poor, monoprice on it’s way from amazon, will take a while).
Now 4K HDR and SDR video work (no black screen) but still riddled with white sparkles, screeching audio from the tv is gone (issue that appeared with the 3m premium high speed cable and was not in the ultra high speed one).
The Monoprice 3m/10ft cables arrived. No real change. 4K HDR/SDR video plays with white distortion and static audio noise from the TV.
Have you tried every input on your display? (Just to rule out a mechanical issue)