AVMutableVideoComposition image overlay low quality

Question

I am creating a feature where a user can record a video of themselves, and superimposed on this video is a view that displays an image and some text. When they are done recording, I am using AVFoundation's composition classes to composite the video and the view (as an image) into one video file, and output this in the next scene in a custom video player. The problem is that while the view's resolution is crystal clear in the record scene, after the composition (and after the AVExportSession completes) the resulting video's overlayed view quality is not clsoe to the actual view quality. I am converting the view to an image, and then setting the contents of an overlay layer as this image's CGImage, which, as I have checked, still has the same quality as the original view. The problem occurs when I apply the composition, and the image becomes blurry. Does anyone have any idea why this might be happening?

If you need to see the code, please feel free to ask! I can also provide screenshots.

Thank you!

Answer 1

It could happen when initiating your UIImage, iOS automatically pick @2x or @3x image source for you corresponding to your device.

Let say you get image size using size property like image.size, it gives you @1x size, and you might reduce your image size from @2x or @3x to @1x, you get a bad quality image output, because JPEG or PNG resize algorithms.