ScreenFlow 8 (and 7) slow 4K preview

Hardware: iMac 27" mid 2010 with 2.93 Ghz i7, 16GB Ram, 2.1TB Fusion drive.

Mac OS: 10.12.6

ScreenFlow version 8.2.2 bought from Telestream.

Scratch disk: Internal custom Fusion drive with 128GB SSD and 2TB HDD

Free space: 1.1TB

1 extra 27" 2560*1440 monitor connected

Source: 4K recording from iPhone 8.


I hadn't done any 4K editing until I had to edit an iPhone 8 recording shot in 4K.

While the program works, it is very sluggish and the preview cannot keep up with the timeline without skipping most of the frames. I upgraded to version 8 partly to see if this issue was resolved, it was not.

I suspect my hardware is too old or there may be another issue with it. I have recently cleared caches in an attempt to rectify this issue while I was using 7. It had no apparent effect.

I switched the thumbnail setting to only show single thumbnails. I don't think it had any effect on this issue.

There is a video action in effect, rotating the video, but it does not seem to have any effect on the sluggishness whether it is on or off.

I attach a screen recording, showing the lagging during playback. Note that I added a mask for privacy reasons.

Any advice is appreciated.

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  • Andreas T said:
    I suspect my hardware is too old

    Yes a computer nearing 9 years old doesn't have the resources to handle 4K H.264 nor HEVC codec the iPhone uses to record. You can disable Thumbnails and Waveforms but I don't think that will be enough. The second monitor is also a stress on scarce system resources so you can remove that as well. Personally I still don't think you'll be happy with the performance after all that.

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  • CraigS Yeah, I kinda figured as much, just wanted the confirmation. Thanks.

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  • Andreas T You're welcome of course. If it's any consolation even the least expensive iMacs today are very powerful.

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