First post. I’ve been using blender for a month and am now addicted. Made an animation of Suzanne being abducted by a UFO. When I save the video to my computer and iPad, it looks great. But when I import it to iMovie on my iPad, portions of it become pixelated. I can fool around with the iMovie editor and other settings to reduce the pixels sometimes, but they always show up in the same two areas (pictures attached). There's also a lot of lag in iMovie. I’ve tried rendering the scenes from blender in both MPEG 4 and QuickTime containers but the pixels are present in both attempts when imported to iMovie. The file format I'm using is "FFmpeg video" and video codec is "H.264". Thanks for your help.
If the pixels only occur after you import your video into iMovie and not in the rendered file on your computer, then it is probably an issue within iMovie rather than with Blender. You can try exporting the scene as PNGs which you can then string together at 24 per second if you are looking for a different format to use. If the rendered scene looks okay when you play it back on your computer, but pixelated upon import to your iPad, no changes in Blender are likely to fix that. Try asking this question in the "Video Production" or "Apple" stack exchanges and they may be able to help better than we can.