How to programmatically compare video quality?

Question

Video

The first user uploads the video, and then the second. Let's skip the comparison of the video from this question, like it was already created here.
And so, we have 2 videos, the first one, since it was uploaded earlier, was encoded, broken into pieces, in general, processed to fit the needs.
And now the second user uploads the same video, and the task is to compare the new video with the previously uploaded one and leave the one that has better quality.

Both videos are the same length, one of the conditions, the second video must be the same length as the first one.

Answer 1

Quality is subjective.
Complex task. Too many factors.
For example, if the quality itself is better (this is a plus), but the author added a video ad (and this is a minus). How to compare this? Or at least added black fields, which can annoy some people much more than the quality itself. Or something is cut off. Etc.
If the second video is just a stretched version of the first one, then it is obvious that there will be no more information in it than in the first one. However, if some video enhancement method was used, then the total amount of information will be more (because the method is also information).
In general, I would partly give it to the users (voting), and partly to the moderators. And the quality comparison algorithm itself would compare only objective parameters to help people. For example, you can signal that the aspect ratio is too different, and so on, which is not difficult to measure in numbers.
You can even combine several simple indicators into one indicator (each has its own coefficient). However, not all factors can be taken into account.