I/O Device Error - Resolve Playing Too Fast

I have an iMac 5k going into a BenQ grading monitor via a thunderboldt to HDMI BM mini mon. I'm using Resolve Studio downloaded from the app store.

I'm having an issue, when Resolve is looking for the I/O device, the media plays twice as fast on my iMac and Resolve says, "failed to set the I/O device". No image appears on my grading monitor. When I tell it to stop looking for the monitor, the images play fine on the iMac (no image on the monitor of course). What is going on? How can I get the image back on my monitor?

[Dwaine Maggart]

In Mac System Preferences, open Blackmagic Desktop Video, and see if it sees the Mini Monitor.

I'm assuming it won't, if Resolve can't see it. If that's the case, you'll need to sort out why.

Try connecting to a different Thunderbolt port, and/or reseating the Thunderbolt cable at each end.

Once Desktop Video sees the Mini Monitor, you can select it again in Resolve Preferences - Video I/O and GPU. You'll need to save the preferences and restart Resolve for it to start using the Mini Monitor.

System prefs does see the mini monitor - its strange, I never had this problem using the same setup on the regular version of Resolve. I just checked and the same thing happens on the regular version. It seems like a weird bug. I just updated Resolve Studio via the app store. Anything else I can try?

I just switched thunderbolt ports on my iMac and the image is back up (for now)!

Hi,

I have this identical issue on my iMac 2015 OS 10.13. Using Resolve 14. All of my projects play back through the Mini Monitor fine, except one. When I open this project, I get the message "failed to set the videomode on the video I/O device." I have tried switching thunderbolt ports...any other ideas for my settings within that particular project that is having issues? Thank you!

[Dwaine Maggart]

If you get that message, it means the Video Monitoring settings are set to something the current I/O device is incapable of doing.

So compare the Video Monitoring settings of a working project to the non-working project, and you should be able to spot what the issue is.

Thank you. I have indeed done that. When I duplicate the settings from another project that operates properly with the Mini Monitor, it does remove the error message but playback still fails. It now plays back in slow motion. So I guess my question should revert to the procedure for resetting the device when editing projects that feature different formats and frame rates. Some of my projects are 1080p 23.9, 30, and 59.9 frame rates. What should my habit be for prepping the device settings before opening each different project?

[Dwaine Maggart]

You generally want your video monitoring frame rate to match your timeline frame rate, for proper playback speed.