XMC-2 AppleTV 4k Dolby Vision flashing screen

[mathew]

My setup is an LG OLED B765 + AppleTV 4k + XMC-2

Until this morning I was able to get Dolby Vision working smoothly; starting today I get a flashing screen in Dolby Vision mode on Apple TV, downgrading to 4k HDR works.
Connecting the Apple TV 4k directly to the LG TV with the same cable works just fine with Dolby Vision.

Anyone experiencing similar issues?

I've tried other inputs on the XMC-2, also the LG (in all combinations, ARC, non-ARC). I've also powered down and reset the XMC-2 to factory settings. No difference.

This is very disappointing. Since all of this used to just work, I'm suspecting something got fried in the XMC-2. Thoughts? 

[Gary Cook]

Please excuse me for being captain obvious but you aren’t using “the same cable”, connecting the ATV4K to the TV uses 1 cable, but with the XMC-2 in there you are using 2 cables. There are 2 possibilities, the first one being the cable that you aren’t using (when you connect the ATV4K to the TV) could be the problem. Secondly, since the XMC-2 has video pass through (ie; no video processing), the cable lengths are cumulative. Hence the 2 cables lengths when added together may be too much for the higher requirements of DV but OK for HDR.

With anything HDMI/HDCP I would always suggest starting at the cables when looking to solve issues.

Cheers
Gary

[mathew]

OK, first off, everything used to work until this morning. Apple TV4k still recognizes the whole chain as Dolby Vision capable and keeps it at that. However, the XMC-2 now has intermittent video.

You're right it could be the cables, but I doubt it.

[mathew]

Aha! Fixed it ..

Here's the sequence:

1. Lowered the refresh rate to 4k/30Hz for Dolby Vision -- this stopped the flashing
2. Upped the refresh rate to 4k/50hz (Dolby Vision)
3. Upped the refresh rate to 4k/60hz (Dolby Vision) -- no flashing!

Something must have set  some state along the chain Apple TV 4k/XMC-2/LG OLED that caused the flashing at 60hz, that was reset when I lowered it to 30Hz.

[Lsc]

Jan 26, 2020 16:51:14 GMT -5 mathew said:

Aha! Fixed it ..

Here's the sequence:

1. Lowered the refresh rate to 4k/30Hz for Dolby Vision -- this stopped the flashing
2. Upped the refresh rate to 4k/50hz (Dolby Vision)
3. Upped the refresh rate to 4k/60hz (Dolby Vision) -- no flashing!

Something must have set  some state along the chain Apple TV 4k/XMC-2/LG OLED that caused the flashing at 60hz, that was reset when I lowered it to 30Hz.

Thanks for this info. When I updated my TVOS on the ATV4K, I was getting this even after I got my new hdmi cables. I restarted the ATV4K a couple times and it kind of went away but I didn’t know the cause.

[ed1950]

Had the same problem with the Apple 4K TV and my XMC-1. Refreshed the rates to 30, 50 and then 60hz for Dolby Vision. Looks like it cured the flashing. Thanks!