Playback in iMovie

HI, so in working in iMovie (latest version) I’ve been dealing with some decently large (1/2 to 1.5gb) files. Playback within iMovie in the window is slow and skips a bit but when exported plays fine. Could it be a limit of my computer (2010 White Macbook with SSD)?

If you are handling 1080p video or above, the processor might not have the performance to render everything for smooth playback in editing.

I’d imagine that’s the case. Given the age of my computer I don’t think it can quite handle it.