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iPhone 11 does not take High Resolution videos?

iPhone 11 does not take High Resolution videos?

I have an iPhone 11 and take a video of myself with the back side of the phone, with 3+ cameras on it.

Record Rate: 4K at 60 fps
Record Slo-mo: 1080p at 240 fps
Camera Capture: High Efficiency

I take the video, then use Adobe Premiere to Export Frame.

The PNG I create looks blurry.

What am I doing wrong?

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Principal Software Engineer
Nothing is wrong.  Video encoding is lossy, which means that it is not a perfect rendition of the scene.  The usual method is to periodically snap a keyframe, then for subsequent frames store JPEG-encoded differences either a) between the keyframe and the current frame, or b) between the previous frame and the current frame.  In either case the further the current frame is after from the last keyframe, the poorer the image quality.  So unless you happen to be looking at a frame which is also a keyframe, the image quality will be about the same as a lossy JPEG encoded picture, with all the fuzz and artifacts of same.

Professional (and high-quality amateur) video equipment relies on special hardware to code the individual frames fast enough that the quality is acceptable.  This isn't practical in a phone.  4K at 60fps is asking too much from a phone; this resolution and frame rate would tax the hardware in anything other than professional equipment.  So the phone does the best it can on that 4K image in 1/60th of a second, which is none too good.

To get a perfect single picture using consumer-grade equipment one must take a normal snapshot and store in RAW or TIF.  (Certainly one can store in other lossless formats but RAW and TIF are the commonly used standards.)  To get a less-than-perfect but high-quality picture one must use a very good encoder at a high quality level.  Neither of these are possible for video; the little CPU in the phone does not have enough memory, horsepower or mass storage to do that for video.
curiouswebsterSoftware Engineer