Blackmagic Forum

I have a problem with using resolve with 4K footage. I have a fairly high spec system, that can handle most 4K footage with no problem at all. For example in premiere I can use multicam sequences with multiple tracks of 4K and it will all playback fine. In resolve dealing with 4K footage has also always been fine up to now. I have bought a decklink mini 4K card so I can output to a reference monitor. The problem I'm having is whenever I play clips in the colour tab, playback frame rate on the reference monitor is always 12 fps (frame rate of my project is 25 fps). Strangely this isn't an issue in the edit tab, where clips playback on the reference monitor at the correct frame rate (I read on another forum post that this is something to do with the edit tab dropping frames to maintain fps). Also if I disable UI overlays in preferences then I get the proper frame rate playback on the reference monitor, unfortunately this isn't an option for me as I need the UI overlays turned on otherwise the LUT I have for my reference monitor, also affects my GUI in the colour tab and affects my scopes.

So I'm wondering what can be done, I've read all the forums and posts where other people seem to be having similar problems, but I can't find a solution. I've been through every option in preferences and project settings that I can try and no matter what the frame rate on my 4K reference monitor is always the same at 12 fps stop I did read in one post someone said it was likely down to the graphics card not being able to handle it, as it was effectively having to output to 2 displays at once, the reference monitor and the GUI. This might go some way to explaining why the frame rate is always 12 fps as that is pretty much half the frame rate it should be (25 fps), and if it is having to display on two screens then maybe that halves performance. Interestingly the way it manifests is that it appears to play a bit on the GUI, and then a bit on the reference monitor, and then on the GUI, and so on and so on. So it stutters on both along at 12 fps. And so back to the other forum post I mentioned where they said it was likely down to the graphics card not being powerful enough, the graphics card I was using was a GTX 1070, and so I thought I would try a more powerful graphics card and have just bought a GTX 1080TI 11 GB which is meant to give approximately 40% performance boost. Having just tried this in my system, there is no difference whatsoever, the playback still stutters along at 12 fps on the reference monitor brackets exactly the same as I was getting with my lower spec graphics card).

As I say there are a lot of similar posts on this subject over the years, and I haven't read that many solutions. I think it might be useful to hear from people who are able to grade in 4K using the decklink card and have UI overlays turned on, and use a reference monitor, and who don't have these issues (in other words they are able to grade 4K without any slow stuttering frame rates on their reference monitor). I would love to know what set up people are using to achieve this. I assume it can't be that everybody is having this problem, so hopefully there is a solution!

It's most likely related to some bug/limitation in Resolve or some resources access issue.
Try moving BM card to a different PCI-E slot.
Are you on latest v15 or v14?

I've tried moving the Decklink card to a different PCI-E slot and no change. I'm on v15 (same in every beta up to beta7) and had the same issue is v14.

Upgrading the graphics card has helped performance in pretty much every other area of Resolve, but made absolutely no difference to this particular issue, no change in the frame rate playback whatsoever, not even a single frame of improvement. Therefore, would seem to me it's not a graphics card issue.

I suspect it's related to the issues with using the LUT for the reference monitor, though no idea why that should be - adding a LUT 'overlay' to the output to the reference monitor can't put that much strain on it can it? And if so where is the bottleneck, as I say would seem it's not the graphics card.

If anyone is successfully using 4K, with decklink, with LUT overlay, then I'd love to know how they're doing it!

At the moment the only thing I can think of to make this work is to remove the overlay LUT to the reference monitor, and buy a 4K LUT box. Any suggestions on what the cheapest 4K LUT box is? At the moment it looks like it's the 'Teranex Mini SDI to HDMI 12G' but that's still another £400, which I definitely hadn't budgeted for.

Hmmm...you are not alone. This issue has been reported many times and atm. I assume this is "Resolve problem", so your external LUT solution may be the only/best one.

Have you tweaked all WIN settings to make PC working at full speed (power plan etc)?
I assume you tried "minimum interface changes during playback" option.

Hi, yes - Windows all set up to run at maximum performance in Power Options and I tried "minimum interface changes during playback" toggled on and off. I think I've tried toggling just about every setting in Preferences and Project Settings, and none of them has had any impact, consistently no matter what I do it just runs at 12 fps.

a few more things to look at;
- are you useing the latest desktop video version?
- are you useing the same raster for timeline and output?

i have decklink 4k, run realtime no problems all day long

my machines have a bit more grunt, but yours should be above the rt bar...

Hi Dermot, thanks for your reply. I am using the very latest version of desktop video (I updated it a few days ago hoping that might make a difference, but it didn't). My timeline resolution/aspect ratio/frame rates and everything matches my output.

With the decklink I am able to run 4K to my reference monitor no problem, with realtime playback, even when loaded with node grades etc. The problem occurs when I add a LUT to my reference monitor:


PROJECT SETTINGS - COLOUR MANAGEMENT - LOOKUP TABLES - 3D VIDEO MONITOR LOOKUP TABLE - (and then my LUT selected)


Do you use a LUT on your reference monitor? If not I'd be very interested to hear if you have the same issues if you do add a LUT?

Thanks again.

Just out of curiosity -- mine if not yours -- did you try the monitor LUT with 4K footage but on an HD timeline and with HD output? My guess is, that won't work either, indicating it's not overwhelmed hardware, but something about the Resolve implementation.

mattwilliams2321 wrote:PROJECT SETTINGS - COLOUR MANAGEMENT - LOOKUP TABLES - 3D VIDEO MONITOR LOOKUP TABLE - (and then my LUT selected)

Why do you need a software LUT for a reference monitor?

mattwilliams2321 wrote: Do you use a LUT on your reference monitor? If not I'd be very interested to hear if you have the same issues if you do add a LUT?

Thanks again.

i have several machines and mon's, so no internal callibration lut applied on any given machine

i use external lut box's on each mon, external scopes and SDI routeing between machines, scopes, mon, recorders

the UHD mon uses a Terrenex lutbox, the HD mon's use Aja

i can test adding a lut and see if the machine is happy

i just made a new project, UHD, linked to a few 5k / r3d files, made a timeline, hit play.. 23.98 all good

went to PROJECT SETTINGS - COLOUR MANAGEMENT - LOOKUP TABLES - 3D VIDEO MONITOR LOOKUP TABLE and added a random lut (BMD's 2383) hit play.. 23.98 all good

with taskmangler open i didn't see any hit on the CPU use - lut in or out, GPU rises by 1% , from 12% to 13%

z820 / dual 12c 2697v2 / dual 1080ti / 128gig / SAS / 4k Decklink Pro

Hi Dermot, many thanks for testing that out! Was your test with 'Hide UI Overlays' unticked in:

PREFS - PLAYBACK SETTINGS

Everything on my system plays fine in 4K on both GUI and ref monitor until I have the following:

- 'Hide UI Overlays' not ticked
- 'Colour Management Lookup Table - 3D Video Monitor Lookup Table' with a LUT selected

If I have only one of either of the above then my 4K plays fine on GUI and monitor, but if I have both of the above it's down to the 12fps.

(I need both of the above as otherwise due to a bug in Resolve the ref monitor LUT also affects the GUI viewer and scopes, which is a known problem).

UHD timeline
UHD monitoring
5k/r3d sources
ACEScct color management
lut in/out
ui overlays in/out
all combo's of the above
every combo plays back @ 23.98

mattwilliams2321 wrote:(I need both of the above as otherwise due to a bug in Resolve the ref monitor LUT also affects the GUI viewer and scopes, which is a known problem).

I understood this to be a feature, not a bug.

Thanks again Dermot, I really appreciate you taking the time to test those.

I think I'm going to give up trying to work this one out and just purchase a 4K hardware LUT box. I've found one for £150 which compared to what they cost not too long ago is next to nothing - "Blackmagic Design Mini Converter SDI to HDMI 6G"

Where is the LUT generated?
What are the specs of the LUT?
Try the LUT in timeline node

Hi Peter, this isn't a LUT I'm looking to use in my project, it's a LUT for my ref monitore (using COLOUR MANAGEMENT - LOOKUP TABLES - 3D VIDEO MONITOR LOOKUP TABLE). This is somewhat related to that same issue I was having with using a LUT for the reference monitor. When it's enabled it also affects the viewers in Edit and Fairlight and scopes in those panels, but not in Color.

It seems, for me at least, when adding this LUT to the reference monitor it also chokes my 4K playback performance in Color to 12fps. If I tick the option in prefs to disable UI Overlays then 4K performance is fine, but then the LUT (meant only for the ref monitor) also affects the Color panel and the scopes.

So, I've decided I'm not having much luck with using the software LUT for the ref monitor and have decided to buy a hardware LUT box - hopefully should have a bit more luck with that.

I get that Matt, but, try it where I said. remove it before render.