Crap! HDMI... :( Help!

[Michael Butash]

So not sure how you ended up here, but I've been doing research, and 
finally pulled the trigger on my desktop upgrade with 3x 4k monitors 
that sadly all only come with hdmi ports vs. displayport natively.

RE: cables, I ended up getting pretty generic, but well rated, amazon 
"hdmi 2.0 compatible" cables, and so far no issues (I thought perhaps, 
but more on that later).  Now, to adapt to DisplayPort...

Since almost no affordable video cards have hdmi 2.0, and especially not 
in any quantity, some research yielded a bit ago club3d, maker of 
various adapters, made hdmi 2.0 to displayport 1.2 adapters that could 
do full 4:4:4 chroma.  A buddy got one as a test with his Sekei 4k/30hz 
tv, but it only did 4:4:2 anyways, but worked well to at least to that spec.

My desktop prior was driving 6x 24" 1080 displays on an asus/amd 7970 
matrix card with 4x DP ports, plus 2x dvi.  I ran my 6 just dandy at 
full 11520x1200 res, now replacing with 3x 48" 4k samsung tv's to do in 
theory full 4:4:4 at 60hz.

Does it work?  Yes, fantastically after some tweaking.  I'm using 3x DP 
ports off the same 7970 card to drive the club3d adapters, to HDMI to 
the TV's.  It was mostly plug and play, I instantly plugged in and saw a 
4k display window.  Adding 2 more went just as well, never rebooting.

So there are a few issues, such as I haven't figured out how to coax it 
to do full 60hz, but I think I found out the issue, just haven't reset 
some things.  Not shabby for a 5-6yr old card, so don't believe the hype 
you need an nvidia 970 card to drive 4k, you just need something with 
the total framebuffer support.  AMD is great about this.

Another weird issue, that I totally thought was a physical issue for a 
while, was apparently stupid amd drivers, again.  I kept getting this 
odd little wobbling effect in parts of the screens, and occasionally 
across the entire tv until I moved the res around some in the amd 
control panel.  I kept swapping cables, adapters, and found no 
reasonable pattern, which lead me to just again crap amd drivers.  After 
some pain to upgrade, downgrade, and eventually abandon the damn blob 
drivers and go with the OSS Radeon drivers.  Holy crap, they work, and 
better than the AMD ever did, and all wobble/fragment/distortion is gone!

The amd drivers worked, but very choppy when moving a big/busy window in 
kde, with compositing off already by default on mine. Enabling 
compositing drove it to a good 10sec lag in seeing a refresh.  After 
moving to radeon, I've enabled full compositing across the full 
11520x2160 framebuffer, with full wiggly effects and everything under 
kwin, and it's literally and beautifully perfect.  GL games seem to work 
fine too, at full res for mega 3-head gaming.

My only remaining issue is apparently there is a long-standing bug in 
4.x that the display configuration widget doesn't save and restore the 
display settings for multi-monitors.  It's a bit cranky when messing 
with it, occasionally causing kwin to glitch, forcing me to drop to 
another tty and restart the session.  I wrote for now a script to setup 
xrandr after startup to move the displays about that seems to work until 
I figure out a better way.

So 4k *does* work, or at least can, but seems mostly up to drivers, and 
oddly, the tv settings as well.  First thing I did was set mine to 
"gaming mode", to lower the input latency, but apparently this has 
ramifications that it doesn't allow full 4:4:4 chroma color if doing 
so.  I think this might be limiting my 60hz too, but not sure.  TBD.

Side note, I might go nvidia now that I'm down to 3x ports again, I just 
need to go gtx960 or higher.  Can't be worse than my 3x pci slot matrix 
card, other than cost, and hoping nvidia drivers are less buggy.  Then 
again, with radeon drivers, I might not have to now.

-mb


On 03/16/2016 10:54 AM, kitepilot at kitepilot.com wrote:
> In my infinite wisdom, I bought yesterday a laptop (Asus ROG GL752VW) 
> and a 4K TV to use as a monitor.
> Stupid Windows 10 would not detect HDMI.
> OK, screw it, I'm going to dual-boot the thing anyway.
> Well, latest-and-greatest Linux Mint (KDE) doesn't detect the HDMI 
> either... :(
> So...
> I bought a 'mini display port-to-VGA' adapter and plugged it VGA into 
> the TV.  It works, but I only get the same laptop resolution (1920x1080)
> ...
> 8-(
> So...
> Questions are:
> 1.- Can I expect my full 4K resolution if I get the #$@! HDMI working?
> and
> 2.- What can I do to get the #$@! HDMI working?
> Thanks!
> ET
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