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Thing is, x264/265 are explicit designed to provide better subjective quality in moving images. For example, x264 will “allocate” more data to parts of the ima

Thing is, x264/265 are explicit designed to provide better subjective quality in moving images. For example, x264 will “allocate” more data to parts of the image that change less, as those remain on screen longer so artifacts on them are more visible. While fast moving parts can be compressed into a blurry blocky haze as they appear for maybe 20 frames so few people will really notice artifacts. (Of course the actual implementation is 100x more sophisticated and complex) You are doing the opposite with PNG’s: focusing on quality of 1 frame instead of on the perceived quality of the frames when viewed as video.

walrus01 6y ago
That's indeed true - and why for subjective eyeball moving picture tests you should also do things like cut out a 20 second piece of a raw/y4m file, encode it with various x265 settings, and then put those 4 or 5 pieces in a VLC playlist so you can quickly compare them in series. For objective comparisons there is of course VMAF, which is an essential tool for doing automated comparisons of videos vs their uncompressed original. One of the reasons why VMAF was created is that subjective eyeball evaluation of codecs (whether still or moving) will vary between person to person, and is very labor intensive. But still image PNGs of frames also serve a useful purpose when dealing with lower bitrate videos, for your personal opinion comparison of blockiness, color banding, blobs of color in areas that are mostly the same color, etc.