I now have a phantom 4 also a mavic air. When I up-load to Facebook and youtube the quality just isn't there. I up loaded 4k, still bad quality. I use Power Director 16 editor. Have had good quality from last up-loads. Please help.
I was reading that YouTube takes the uploaded video and creates several different resolutions so every viewer, no matter their internet speed, can watch without interruption or buffering. The lower resolutions are available sooner than the higher ones. They also recode the videos to better match their servers.
Try uploading to Vimeo and see if there is a difference. Those videos seem to look better to me over YouTube.