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iMovie pixelated video for a few seconds at or after transitions (Cross Dissolve).

Problem with iMovie, pixelated video for a few seconds, mostly at or after transitions (Cross Dissolve). Sometimes it also seems as if a “frame” from the earlier video appears immediately after the transition. Example below.


1.     Looking as other forums, some similar issues suggested corrupted files, I have tried re-importing effected video. 

2.     As problem appears to be around the use for the Cross Dissolve, I have tried removing them and using different or no transition.


The above can solve the issue "sort of" however, the problems then appear in other parts of video. The strange thing is in preview the video can show pixelated video, then if I go back and “re-preview” this problem can disappear, but then reappear if a watch back again?


Another forum suggests resetting the defaults in iMovie then reopening library (did not help in this case)


I had my library stored on SSD external drive via USB3, tried copy paste project to new iMovie library in internal drive, but no change. 


Tried importing to a trial version of Final Cut Pro – same problem.


I have opened old projects, previously unaffected with this problem, this pixelated video at cross dissolve now appears in a few parts.


Build & Versions

·      iMovie 10.1.14 Build 358560

·      iMac (Retina 5K, 27-inch, 2019) Memory 40 GB 2667 MHz DDR4

·      macOS Catalina 10.15.2

·      Video and photos taken with iPhone XS and XR.

·      iMovie film c16 minutes long, audio is not affected in any way.


iMac 27", macOS 10.15

Posted on Dec 14, 2019 4:37 AM

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Question marked as Top-ranking reply

Posted on Dec 14, 2019 8:39 AM

Hi, CDSnap,


The pixellation/artifact issue has been reported several times on this forum. Take a look at this thread:


https://discussions.apple.com/thread/250751600?page=3


There seems to be some correlation with the appearance of the pixellation and iPhone movies recorded with the HEVC format. If this is your situation you might try changing your iPhone settings to Photo/Transfer to Mac or PC/Automatic. That would give you a more compatible format. Or, you could try using the free download, Handbrake, to convert the videos to H.264, Mp4/AAC and then import the converted videos into iMovie.


-- Rich

Similar questions

10 replies
Question marked as Top-ranking reply

Dec 14, 2019 8:39 AM in response to CDSnap

Hi, CDSnap,


The pixellation/artifact issue has been reported several times on this forum. Take a look at this thread:


https://discussions.apple.com/thread/250751600?page=3


There seems to be some correlation with the appearance of the pixellation and iPhone movies recorded with the HEVC format. If this is your situation you might try changing your iPhone settings to Photo/Transfer to Mac or PC/Automatic. That would give you a more compatible format. Or, you could try using the free download, Handbrake, to convert the videos to H.264, Mp4/AAC and then import the converted videos into iMovie.


-- Rich

Jan 21, 2020 2:34 PM in response to MiamiBourne

Not yet, I have continued editing videos in iMovie with my existing iPhone XS video files from last years holiday - some work some don't - there is no apparent pattern why. For new files, I have switched to "Most Compatible" from "High Efficiency" in iPhone camera settings - but I can't say for certain this is root cause and I have no solution for existing video files. I have just bought a GoPro and will try video from this and new iPhone XS video shot in Most Compatible and will share results - but might take me a few weeks to find time to do.

Annoyed this problem continues, spent ages trying to fix, will update with my findings shortly.



iMovie pixelated video for a few seconds at or after transitions (Cross Dissolve).

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