Blackmagic Forum

I just loaded Resolve Studio 17 Beta today hoping that a performance issue when using multiple displays in Fusion would be resolved, but sadly it remains. I'm wondering if there's a setting I'm missing, or if anyone has any insight into what's causing this issue.

Having just installed a new monitor equipped with both HDMI and Displayport inputs, I prefer to use the Displayport connection for more flexibility and tighter integration with my iMac's display controls. However, when working in the Fusion page performance is horrible. Playback is not smooth enough to be useful and the responsiveness of the entire user interface is frustratingly slow.

This only occurs when I have the workspace configured for dual screen mode. Dual screen mode performance is fine in the edit page.

If I connect the second display using the HDMI input performance is still slower in dual screen mode, but not intolerable. Playback is choppy but I'm still able to judge timing fairly well, and the user interface has only a slight lag. However, when connected via HDMI my iMac provides fewer screen resolutions so the text on the second display is either too big or so tiny I have to squint to read it.

Any idea what would cause this behavior or how to work around it?

Here's an update on display performance on the Fusion page:

I see reduced performance during playback - on the Fusion page only - where it plays 1 frame every second at 1 second intervals on the timeline. In other words, the timeline indicator also jumps at intervals of 1 second along the timeline. The user interface performance also lags to the point that clicking in any node’s numerical entry boxes isn’t recognized for a full second, and adjusting numerical settings by scrolling is unusable.

I've narrowed the problem to:
The Fusion page only;
When running in dual screen mode;
With iMac set as the primary display, and ViewSonic VP2785-4K monitor set as the secondary display;
When either the Spline or Keyframes window is open.


If any of the above conditions are not true, performance is fine, However it’s worth noting that reversing primary and secondary displays solves the performance problem, but if I send the video clean feed to my iMac display I lose all access to the Resolve menu, so there’s no way to turn it off - or even quit the program - until I disconnect the second display, force quit the program through task manager, and re-open with the second display disconnected. That seems like a BUG.

Display Interface Dependancy:
Performance is degraded when the second display is connecting either directly by Thunderbolt 3, or Thunderbolt 3 to DisplayPort adapter.

Performance is reduced, but acceptable when connecting via Thunderbolt 3 to HDMI connector.

Display resolution has no influence on performance.

It occurs in both Resolve 16.2.7 and Resolve 17.0 Beta running on Big Sur OS.

I first noticed it after installing a new monitor on Resolve 16.2.7. I installed Resolve 17 Beta hoping the issue would be resolved as part of performance upgrades in the new software. It does not occur on my older MacBook Pro with Resolve 16.2.7 and is also running on Big Sur.

Any insight as to what causes this problem would be greatly appreciated.

Another update: the performance issue on the Fusion page only seems to happen when the keyframes and/or spline panels are open on the secondary display. If I select my Viewsonic VP2785-4K as the primary display I can display both panels on my iMac and the performance is perfectly usable.