I've noticed I have chroma subsampling artifacts in the realtime preview while editing in Kdenlive:
https://imgur.com/a/WJGoe

I wonder if it's done to speed up realtime preview, or if MLT is actually encoding a video stream to be used for realtime preview?
If so - isn't this a waste of resources? Wouldn't it be faster and cheaper to give Kdenlive access to raw frame buffers instead of encode a frame and have Kdenlive decode it for display?

I'm just curious why is there chroma subsampling in realtime preview.