What you’re seeing relates to a couple of things.
First, X operates on a system where as soon as footage is imported, it grabs it and no matter the original type of footage nearly instantly creates a limited resolution viewable version and makes that available for you to edit.
This is great because you can get to work FAST.
Then it starts working in the background to transcode the footage into a better version for your editing purposes. How much work it has to do depends on the format it was originally shot in – and what format you’ve set your timeline to use. (X is optimized for ProRes, so many use that as the “native” timeline codec – and if so, all the imported stuff has to be transcoded to that before your timeline becomes “native.”‘
Also, X has a menu choice that lets you decide if you want “faster performance” or “higher quality display.”
All of this is just how X works. It brings in stuff – lets you get to work fast – then goes to work in the background to do the complex calculations needed to finalize things.
So it’s really common for people to get fooled, since they think that because their footage “looks odd” inside the software, that’s how it is.
To get a better idea of what your footage really looks like before rendering, park your playhead anywhere on your timeline and let X render out the frame to your display. This should happen rapidly and will show you the underlying quality you have set in your preferences better than a motion stream.
Hope that helps.
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