Haha, that's a great point! On that note - do you have any good pointers on understanding more about how Butteraugli works? I wholeheartedly agree it is a great metric (which aligns well with my subjective assessment much better than MSE or MS-SSIM), but the Guetzli paper (or the Butteraugli GitHub repo) does not explain the theory behind it in detail.

Seems like others were curious too, given the Wikipedia page on Guetzli mentions:

> Butteraugli. ... How the hundreds of parameters that model the properties of the human visual system were derived remains unexplained.

My rough understanding is its multi-scale convolution architecture was inspired by biological visual perception (perhaps how the layers of visual cortex gradually represent higher level features, ish), and involved some sort of empirical parameter tuning based on human evaluations. It'd also be a very nice resource for beginners wanting to learn more about image/video codecs (like me :)