4K playback slow - 4K-SDI makes it worse

Hello,

I recently bought a Decklink 4K SDI and a miniconverter for my 4K monitor to view and grade the footage from my Production cam in its native resolution. But with 4K I experienced problems with stuttering playback. Today I did some tests and made some interesting findings.

I can't get 24p ProRes 4444 (4K DCI Scope) to play back realtime in Resolve. When having a 2K timeline + 2K output I get about 19 fps. 1 or two less with 4:4:4 over 3G-SDI, about 3 more with Full HD. When switching to 4K (DCI Scope) and 4K 4:2:2 over 6G-SDI I'm only left with about 13fps. The file plays nicely in Quicktime and the same ProRes file converted to 4096*2160 with letterboxes for Media Express compatibility plays also nice on Quicktime and MediaExpress with its 24p without stuttering. Note: No grade, LUT etc. active in Resolve. No noteable difference with scopes on/off.

How comes Resolve isn't able to play realtime when other software does?

The machines hardware is:
Intel i7 950 4*3.06GHz, Gigabyte X58-UD3R mainboard
3*3 TB RAID0
Resolve 11.3.1 (OS X 10.10) / Resolve 11.2.x (OS X 10.9)
GeForce GTX 780 6GB (in true PCIe-x16 slot)
Decklink 4K-SDI card (in true PCIe-x16 slot)


PS: Removing my previously installed Geforce GT 640 GUI card btw. seemed to improve the playback speed by about 1 frame.

When you play, check the cpu load: is it high?

[Rohit Gupta]

Hello,

I recently bought a Decklink 4K SDI and a miniconverter for my 4K monitor to view and grade the footage from my Production cam in its native resolution. But with 4K I experienced problems with stuttering playback. Today I did some tests and made some interesting findings.

I can't get 24p ProRes 4444 (4K DCI Scope) to play back realtime in Resolve. When having a 2K timeline + 2K output I get about 19 fps. 1 or two less with 4:4:4 over 3G-SDI, about 3 more with Full HD. When switching to 4K (DCI Scope) and 4K 4:2:2 over 6G-SDI I'm only left with about 13fps. The file plays nicely in Quicktime and the same ProRes file converted to 4096*2160 with letterboxes for Media Express compatibility plays also nice on Quicktime and MediaExpress with its 24p without stuttering. Note: No grade, LUT etc. active in Resolve. No noteable difference with scopes on/off.

How comes Resolve isn't able to play realtime when other software does?

The machines hardware is:
Intel i7 950 4*3.06GHz, Gigabyte X58-UD3R mainboard
3*3 TB RAID0
Resolve 11.3.1 (OS X 10.10) / Resolve 11.2.x (OS X 10.9)
GeForce GTX 780 6GB (in true PCIe-x16 slot)
Decklink 4K-SDI card (in true PCIe-x16 slot)


PS: Removing my previously installed Geforce GT 640 GUI card btw. seemed to improve the playback speed by about 1 frame.

You need to make sure your output resolution (normally defaults to same as timeline resolution) is same as your video monitoring resolution for optimum performance.

You need to make sure your output resolution (normally defaults to same as timeline resolution) is same as your video monitoring resolution for optimum performance.

The timeline is 4K DCI Scope, Monitoring 4K DCI as the monitor is 4096*2160 native.

When you play, check the cpu load: is it high?

It was about 300-400% afair. In Media Express I had a bit more but I'm far away from the 800% max on this 4core + hyperthreading CPU. Was the first thing I checked if the CPU is near its limit.

[Rohit Gupta]

You need to make sure your output resolution (normally defaults to same as timeline resolution) is same as your video monitoring resolution for optimum performance.

The timeline is 4K DCI Scope, Monitoring 4K DCI as the monitor is 4096*2160 native.

When you play, check the cpu load: is it high?

It was about 300-400% afair. In Media Express I had a bit more but I'm far away from the 800% max on this 4core + hyperthreading CPU. Was the first thing I checked if the CPU is near its limit.

Set your output res (3rd tab in Project Settings) or timeline res to 4096*2160, and you should get good performance.

Set your output res (3rd tab in Project Settings) or timeline res to 4096*2160, and you should get good performance.

You mean output scaling?

I did some more tests: So without the Decklink activated (set Video I/O card to None in the Preferences), I get realtime playback. With 1080p and 2K resolution (set the output [Video format] to this resolutions and set output scaling to the corresponding size) I was now today able to get realtime. Without output scaling but with "Video format" on 1080p/2K I get about 20/21 fps in the kind of middle zoom. Why is this? Shouldn't this be faster cause no transforming has to be done? And with timeline and video format on 4K p24 and Output scaling on "Match timeline setting" I get 14-15 fps.

The CPU is between 350 and 500% in all modes. Menu meters shows only minimal memory usage on the GPU but processing is at about 55-70%. (I don't know how reliable menu meters GPU meter is, especially with inofficial cards.)

For me it's important to find out what the bottleneck in my setup is. I'm going to build a new workstation in summer and want to know this before.

PS: Just had the idea to copy the clips onto a SSD and boot my windows install to test the performance there.

Results of my windows test:
On Windows I have between 10-11 fps for the 4K with 2K output and scaling to 2K and 5.5-6.5 fps at 4K. CPU is on full load with 2K output and about 60-70% in 4K. GPU Load and Memory are a non-issue due to GPU-Z monitoring.

Seems Resolve on Windows is much more painfull or why is the load so much higher? Was planing to use windows on my coming workstation due to the lack of Resolve for Linux with the standard dongle.

[Peter Chamberlain]

Hi, im not sure from all the above about your config.
Try setting the output scaling to match the timeline settings.
Then, set the timeline settings to match your monitor res which i think is 4K-DCI.

Which DeckLink driver are you using?

Hi, im not sure from all the above about your config.
Try setting the output scaling to match the timeline settings.
Then, set the timeline settings to match your monitor res which i think is 4K-DCI.

Which DeckLink driver are you using?

I did this with the 4K-DCI Timeline and output resolution. I'm using the 10.4 driver.

FYI I've done all the tests you can imagine in your circumstance... I've come to this conclusion.

Activating the Decklink will affect general performance not matter what you do. It'a as simple as that...

You'll probably need more GPU to counter act this.

Essentially, Resolve is managing 2 different outputs. You can try the HIDE UI OVERLAYS FOR OPTIMISED PLAYBACK in the video monitoring options. Be careful if you are using a LUT to calibrate your display. This function will add the LUT to your scopes.

Cheers!

Chuck B.
Montreal, QC.

FYI I've done all the tests you can imagine in your circumstance... I've come to this conclusion.

Activating the Decklink will affect general performance not matter what you do. It'a as simple as that...

I know. But it’s not only activating the Decklink. Resolution seems to mater very much.

You'll probably need more GPU to counter act this.

I’m not doing any processing right now and the GPU is far from work-saturated. Not even my monitor out LUT is on in my tests. (Which when I had switched it on didn’t seem to change playback speed at all!)

May the PCIe 2.0 be a problem? From my calculations it shouldn’t be a problem bandwidth wise at all but on the other side I don’t know what exactly Resolve is doing in the Background.

Essentially, Resolve is managing 2 different outputs. You can try the HIDE UI OVERLAYS FOR OPTIMISED PLAYBACK in the video monitoring options. Be careful if you are using a LUT to calibrate your display. This function will add the LUT to your scopes.

Have to try this option when I’m back home. Output LUT is now problem. Yes, by default output LUT is applied to scopes too but you can set another or no LUT in the LUT configuraiton panel for the scopes.

Btw. is there a way to deactivate the GUI preview to only have one output for testing?


As I wrote earlier I’m planning my next system currently and would like to find out what the key points are to get more performance. Basic will most likely be a dual Xeon board with one 8*2.6 GHz Xeon for the starts and the later addition of one more maybe. GPU wise I have planned to take my GPU over for now, as my wished setup (2-3 Titan X) are a bit expensive

A small follow up about something that made me even more confused:

Yesterday I started Resolve to just test the video levels on exports from FCPX in ProRes vs. Tiff. Playback was Realtime with the ProRes and suddenly I realised, that the output was Video levels (monitor expecting Data-Levels). After switching Playback performance dropped from 24fps to about 22fps (HD Output).

Then I switched to 4K output and tried Video vs. Data levels. Playback in Data levels about 15fps as I wrote earlier. Video levels was about 17fps or so. So where may the problem be? Doesn't make sense for me that this setting changes playback so much!

Hello

Did you made any progress here. Turns out our playback issues was in part hugely because of the decklink 4k extreme. =(( haven't attacked it yet but stumbled over this thread and thought I'd ask.

Thanks!

Did you made any progress here. Turns out our playback issues was in part hugely because of the decklink 4k extreme. =(( haven't attacked it yet but stumbled over this thread and thought I'd ask.

No progress here. Talked to BMD at IBC this year and as far as I got it the problem is that for this they have to access data from the GPU at two stages and this takes it's time. Maybe it sometimes improves a bit but nothing yet really...