4k@60@4:4:4 - Macbook Pro 15" Late 2013 with Nvidia GT750M - refresh rate/chroma Issue


#1

I have got the latest http://plugable.com/products/mdp-hdmi/ with the above laptop and a Samsung UE40KU6400. Using switchresx I have the following questions/issues I’d appreciate some feedback on.

  1. I can’t push refresh rate above 50Hz. I lose display completely with the tv saying no output detected.

  2. Not sure if related, 50Hz is fine but weirdly 30Hz picture quality is poor but 25Hz looks fine. 30Hz looks like someone has put a filter over the whole display

  3. I can’t get 4:4:4 chroma subsampling to work. I’ve enabled UHD color on HDMI1 but using test images I can clearly see it’s running 4:2:2.

Thanks

Paul


#2

Hi Paul, thanks for posting. Unfortunately, 4K@60Hz is tricky within Mac OS and we may not be able to resolve all of the issues you are experiencing, but I am happy to help investigate what may be happening. As it seems you have found, using SwitchResX or other 3rd party applications must be used on previous Mac systems in order to create a custom resolution to achieve 4K at 60Hz, however, in our experience some customers have better results than others.

That said, would you be able to let us know the specific HDMI cable that you are using? I’d like to confirm that it is HDMI 2.0 capable in order to support 4K@60Hz and 4:4:4 chroma.

Also, would you happen to know the color depth “bpc” setting that your graphic settings our running? Our adapter can only support 4K@60Hz with 4:4:4 chroma at an 8bpc as defined by HDMI 2.0 specification (http://www.hdmi.org/manufacturer/hdmi…). Anything above 8bpc is limited to a 4K@30Hz refresh rate.

Thank you,

David W.
Plugable Technologies
www.plugable.com/support


#3

Hi David, thanks for responding.

Regarding the cable I’m using, i’m not sure of it’s origins but it’s marked as a high speed cable. Just in case I’ve ordered a new cable (https://www.amazon.co.uk/d/ms5/IBRA-S…) so will give this a try as soon as it arrives.

Regarding bpc, i’m using the “millions of colors” option in switchresx.

I’ve had a further play and I can actually get an output at 60Hz after tweaking switchresx (http://pasteboard.co/6ht62PNlU.png) but the picture loses all sharpness similar to that seen at 30Hz. Not sure if that is any help.

With regards to 4:4:4 chroma, even dropping down to 25Hz is no help, it’s clearly running in 4:2:2. Switching to 1080p fixes the chroma issue.

If these sound like possible cable issues then hold fire and i’ll report back in a couple of days and let you know how I get on. If changing the cable has no effect I’d be interested to know if you think the mdp->hdmi adapter could be at fault. I’ve seen reviews of other adapters on amazon where users have managed to get 4k@60@4:4:4 with the same mbp and similar switchresx settings.

Regards

Paul


#4

Hi Paul, thanks for the update and additional information. Curious to hear the results with the other cable, although you are able to achieve 4K@60Hz with the current one, this may not have an impact.

Pending the results with the other cable, one thing we can try is to make sure that the adapter’s firmware is up to date. Unfortunately, the firmware update tool from our engineers can only be ran on Windows operating systems. If you happen to have a Windows system I would be happy to arrange instructions and send you the update utility and firmware file. If you do not have a Windows system, we can send you a replacement cable that we have tested and ensured that the latest firmware is loaded. Regardless of the method, we would then contact you directly via email to make arrangements and then update this forum thread with any updates that we may find in order to keep communication in one place.

Thank you,

David W.
Plugable Technologies
www.plugable.com/support


#5

Hi David

I wouldn’t say 4k@60Hz was usable due to the output quality, it looks like it’s out of focus/hard to describe. I can try and take a picture of 50 vs 60 to demonstrate if needed.

I do have access to a Windows system though so if you want to send through the update utility and firmware file that would be great, it’ll be something else I can try while I wait for a new cable.

Regards

Paul


#6

Hi David

Thanks for sending the firmware through. Unfortunately updated hasn’t had any effect. I’ve also tried my new cable and still the same issues.

As another test I also plugged my laptop into a 4k monitor which has a displayport input and I got 4k@60@4:4:4 with no issues using the same switchresx settings so it does look like it’s the displayport to hdmi adaptor that is the issue here.

Regards

Paul


#7

Hi Paul,

Thanks for the reply. Sorry to hear that things still are not working after the firmware update and trying the new cable.

Unfortunately, I am running low on variables to check. The only thing left to try is to send you a pre-tested replacement adapter to make sure that the hardware within this specific adapter is working properly. Please let us know if you would like to try a replacement adapter or if you would prefer a return for full refund and we can reach out to you directly to facilitate.

Thank you for your patience,

David W.
Plugable Technologies
www.plugable.com/support


#8

Hi David

Thanks, let’s try a replacement, let me know what you need.

Regards

Paul


#9