frames were dropped during playback

Hello

I have a Late 2009 iMac 2.8 GHz Core i7 16 GB 1333 MHz DDR3 ( ATI Radeon HD 4850 512 MB)
I have a 500 GB SSD with an extra 1TB internal drive for my files.

So I have shot some footage on a Sony action cam (FDR-X3000) at 120 fps (1920x1080) foolishly.
The files are in MPEG-4 Codec H.264, Linear PCM.

The footage is on my internal 1TB drive, when I import into FCPX 10.3.4 and go to view the clip I get a warning telling me 'Video frames were dropped during playback'.

There is a little icon in the clip, top left corner - small grey box with dashed circle

The footage is very jumpy not smooth, however the sound seems good.

Please advise - Thank you in advance.

"There is a little icon in the clip, top left corner - small grey box with dashed circle"
Can you do a screen shot of that?

I'd not sweat dropped frames, turn that warning off in the Preferences. Frames get dropped all the time, no big deal, if you don't notice, it ain't hurting anything.

I'd put the Library and media on a secondary, very fast drive, not the system drive. The OS and apps need that bandwidth.

MPEG is a "Long-GOP" codec, super highly compressed, takes a LOT of CPU power to play it back, so nothing unusual there. Yeah, turn that warning off, ignore it, you'll be fine. Hasn't caused me any issues since legacy FCP.

I had the same machine, I only upgraded the VRAM to 2GB (flashed Nvidia GTX). You should use Optimized Media (Import check box ), then you can edit anything (though UHD not very comfortably). You can also transcode to Proxy, then there are no limits.
Always wondered about the dropped frames warning. This was relevant when you edited "to tape". But FCP X doesn't offer that anyway.

If you're editing high end film work for a major Hollywood feature, there are editors who insist on seeing every single frame. But for the rest of us, playback is good enough to edit just fine, and export is not effected at all. UHD and fast frame rate clips are going to drop frames, but you'll never notice it. As Axel points out, we're not matching back to film (or tape) anymore... thank goodness.

Warning, use either Optimized or Proxy, not both.