I have a pair of video clips (mp4) that I would like to join into 1. The internet tells me that I can do this with Quicktime.

Unfortunately, whenever I try exporting joined clips, with clips of any size, I get the same error:

enter image description here

"The operation could not be completed; an unknown error occured"

If I try to save, rather than export, I cannot. But if I try and close, I'm given an option to save. If I choose to save then, I get this error:

enter image description here

Can anyone tell me where I'm going wrong?

For full information: there is a two minute video of me running into the problem here

  • 2
    Same, Problem remain for years, never get fixed and response.
    – kitta
    May 2, 2019 at 9:15
  • Same here. Apple is crazy for not fixing this.
    – Staxxx
    Jul 30, 2019 at 23:32

1 Answer 1


It's not working because the video is compressed using an incompatible codec, why apple has ignored this for 3 years is beyond me. I used VLC

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