FCPX MP4 playback choppy on 5k iMac buttery smooth on Samsung TV

[pcconvert]

Sorry for complicated title. I am creating a movie in FCPX with Ken Burns effects on stills. Timeline is 24fps UHD and another one 1080p. Resulting files are MP4 for Apple devices and also MP4 for computer. The puzzling thing is that when I play these files on 5k iMac (295X video card) I am always seeing choppy transitions and Ken Burns effects. When I play the same files on my Samsung uhd-un65hu9000 TV from an SD card reader the very same files play buttery smooth. So it's great that the final product - the movie played on TV - is nice - but how can I see this product on OSX? Quicktime or VLC - no difference.

Edit: Ok, I got this. Exporting movie with 60fps solves the problem on OSX - it's smooth. Or I guess using Switchres to set the display to 24 hertz (didn't try this one)...

 

[joema2]

When you play it in FCPX it is probably not rendered. You can select the timeline and press CTRL+R to render it, then it will probably play smoothly. Similarly, exporting it to an output file will automatically render all effects and the resultant MP4 file should play smoothly on your Mac.

You also mentioned UHD which is 4k. That is very difficult to edit, even on a high end iMac. I have a 2015 top-spec iMac and I always transcode to proxy media when editing 4k.