Uploaded an iMovie to YouTube of my recent trip to Iceland. Took 5 hours to upload the 14 minute 4K video. Some drone shots, some iPhone shots. The video on iMovie looked pretty decent for an amateur like me, having the MA about 3 weeks before the trip! After waiting the 5 hours for the upload, the video was finally posted, I quickly watched it and it looked like crap!! Grainy as could be. Disappointed I googled what the problem could be- found out it takes about 10-60 minutes for Youtube to do it’s final rendering. After that time had passed it now looks good again. Happy with the final outcome!