Hi all,
I’ve installed CoreELEC 9.2.5 image to eMMC and see sometimes random distributed colored pixels during 4K HEVC playback. The phenomenon appears like I experienced using overclocked graphic cards in the old times. This mostly happened with over-driven VGA RAMs. The SOC temperature is 52 Celsius so the heat mustn’t be a problem. Is it possible that the LPDDR4x RAM on board is defect? How may I test it? Does anybody see similar defects?
Hello, how did you write your coreelec?
To remove doubts, you can check your videos, for example, from the Android system.
Hi Vladimir,
I’ve wrote the official KHADAS image from repo to eMMC. To be clear I’ve an S905X3 device which plays 4K HEVC without a glitch.
I understand, but we need to check a311d, I suggest you record the latest stable version from the coreelec website, and see how it behaves with a standard record to sd / usb.
OK I will do a test with official CoreELEC first. Is there a similar tool like memtest86 on ARM systems?
At the moment, I advise you not to consider any kind of test programs, first you need to try all the standard coreelec recording options, then, we will be able to draw conclusions and proceed to further steps.
Something similar can be found on Android.
If you are afraid of losing data, I advise you to make a backup, coreelec provides this function.
@karmantyu if the video keeps stuttering the the same place, its definitely not due to bad memory,
though memtest exists, it needs to be enabled in the kernel defconfig and recompiled…
its probably just a issue with the video encoder, you should more importantly inform on the CoreELEC forums, as the issue is way more applicable there, and the support might be more profound… 
By the way, perhaps this may somehow be related to your settings of the coreelec itself, here you need to look at the default to begin with.
@Electr1 There is no stuttering. I experiencing a better, smooth playback than on S905X3. First will test with CoreELEC from official CoreELEC distro as @Vladimir.v.v suggested.
Oh I’m experienced with Libre and CoreELEC, I will know if the settings are the culprit.
It is hard to catch the error, so made a clear screener and circled the error in an editor.
If you find some problem you can come to CoreELEC forum where all the help will be provided.
It reminds me of broken pixels on the matrix, I hope this is not so! 
It’s okay, I think you can solve the problem in parallel on two forums, maybe it will be just as useful for someone!
Of course, it’s important that whoever has the same problem finds a thread with a solution. Not just an abandoned one.
Yes, that’s right, you need to share information with each other, regardless of the source!
Hi all,
I had half an hour again to testing. The new nightly (01202021) seems to play 4K HEVC without glitch too. Set up type 1 buffering in advancedsettings.xml for further testing but everything played nice again. Under System/CoreELEC switched on ’disable NR’ and that had no problematic effect on the playback.
Booted to stable KHADAS CoreELEC 9.2.5 on the eMMC again and under System/CoreELEC switched off ’enable HEVC seek workaround’. For surprise the random distributed colored pixel errors were missing completely. My test was not extensive, only a short one but maybe fund the culprit.
I will report back with final conclusion.
In some cases, resetting to factory settings gives a positive result, and it is not always clear what could be the reason for the problems.
Found the definite culprit.
Random distributed colored pixels when playing high bit-rate 4K HEVC content on a311d with CoreELEC 9.2.5 is not a hardware problem. Switch off under System/CoreELEC ’enable HEVC seek workaround’ and the problem will be gone. Thank you for all of your assistance.
There is a bug with a hardware decoder enable on corelec since the beginning. If you disable it, you can see the hevc videos correctly.
go to kodi settings, player/settings/ render method and disable amcodec.
