How to compare two transcoded videos using SSIM metric?

Question

fmpeg

Hello!
There is a video original_720p.mp4. Two videos with presets were transcoded from it, for example, medium and fast:
1. transcoded_360p_medium.mp4,
2. transcoded_360p_fast.mp4.
How can I compare two transcoded videos by SSIM metric? Now I compare them like this:

ffmpeg -i transcoded_360p_medium.mp4 -i transcoded_360p_fast.mp4 -lavfi ssim -f null -

After processing the command, I get some SSIM value, for example, 0.985001. However, if I swap the video links in the command above, I get exactly the same SSIM value. In view of this fact, it becomes unclear which video is better in terms of SSIM.
Maybe I missed something? Please advise how to identify the best video.

Answer 1

Chota rzhu)
Pairwise comparisons of the recoded videos with the original were missed.