[Odroid C2] HDMI flickering (black flash) issue

Hello CE community.

I have an issue which starts to be seriously annoying. From time to time, during a video playback (tv show / movies) the screen goes black for a couple of second and then video continue to play.

I’ve found some threads with same issue, tried a looot of things, but nothing work.

  • Tried both LE and CE
  • Changed HDMI cable
  • Remove everything was plugged on C2 usb
  • Changed HDMI port on TV (Samsung UE58RU6105)
  • Changed color settings on TV / Kodi

I’ve not been able to understand when it occurs, can be every few seconds, or never during a whole movie…

So far, the only things which works is :
echo 0 > /sys/class/amhdmitx/amhdmitx0/output_rgb during a playback. It does one more flash but usually solve it for, at least, the end of the movie.

Yes, I know, some threads about similar issues recommend to echo 1 to force rgb, what seems to work for me is 0.

Dispinfo is here : http://ix.io/2iUg

Hope we can find a solution for this.

I’ve seen this too on my N2. In my opinion, I think it appeared in some nightly build between 9.2.1 and 9.2.2, much closer to 9.2.2 than 9.2.1. Too bad I didn’t note it then as I use the box only occasionally.

I have this issue, and had it with 9.2.1 (official). Tried various nightlies along the way to 9.2.2 - all still have the issue, and still have it currently.

It’s very annoying.

I just can’t pin it down. It doesn’t really seem like hardware as a reboot will solve the issue (for a while at least).

I really don’t think it is bandwidth related - I can play 4K movies just fine. It’s just as likely to happen with the Kodi UI (1080[/50 in my case) - as during playback (if not more so - indeed the pictures screensaver is one of the main things that seems to set it off).

I can’t find anything in the Kodi logs about it, it doesn’t even seem to think anything is happening, so feels lower level…

I reckon it is this issue of PLL drift:
Solved in some builds here apparently:
“My custom build contains new PLL settings for HDMI, these are shared by AMLogic. It’s just a code with understandable constants for particular registers, so I thought it is meaningless to share at the moment. Obviously it will be opened to GIthub when this changes helps to fix HDMI issues we have.”

It definitely sounds like very much the same issue.

Would the above give team Coreelec the sort of info they might need to look at this issue?

Apparently it was an issue with Pi devices to:

"Or if the clock is being kept to frequency by a PLL, and the PLL has wider tolerances than some HDMI devices like, it may be that it is drifting a little too much? (I think this was the issue with the Pi / Pi 2 and AVRs where we were getting black flashes, and a config parameter allowed you to reduce the amount by which the HDMI clock could drift? The drift was intentional to allow for small video or audio timing errors to be corrected without dropping / repeating frames?):

… more here: https://forum.odroid.com/viewtopic.php?t=11837&start=100

It is indeed a bandwidth issue because at 1080p 60Hz, it defaults to a higher chroma setting, whereas for 4K 24 Hz it uses a lower chroma setting.

I was having the exact same issue and I solved it by adding the following line to ~/.config/autostart.sh

echo 422 > /sys/class/amhdmitx/amhdmitx0/attr;

It forces YUV422 on all modes.
Moreover, this problem was resolved when I upgraded my TV/receiver. So, it appears that the problem was with the TV/receiver rather than the cable.

That seems wrong / over simplified to me…

1080p even at 4:4:4 / 60hz / 10 bit still uses less bandwidth (< 9 gbps) than any 4k signal, even 4:2:0 8 bit 24hz (~9 gbps).

Not saying your fix might not work, and glad it does for you, but it’s not sheer bandwidth if so.

There’s something more complicated going on, for at least some of us.

Did it work for you?

Was night time here, will try it tonight and report back.

Also, the problem is intermittent so hard to be sure for a bit.

Too early to be sure, but tonight was flicker free…

Ok, no flickering for some time now.

I’ll take a working fix over something logical any day, so thanks for pointing me in the right direction.

I guess my receiver (most likely, it’s from 2014, although it does claim support…), or possibly tv just doesn’t like 4:4:4…

Thanks again!

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