Binary interface to the Rust implementation of the SSIMULACRA2 metric: https://github.com/rust-av/ssimulacra2
The following is a rough estimate of how ssimulacra2 scores correspond to visual quality.
sudo pacman -S vapoursynth vapoursynth-plugin-lsmashsource gcc make cmake pkg-config ttf-bitstream-vera # Keep install dependencies
See http://www.vapoursynth.com/doc/installation.html#linux-installation
Install l-smash from https://github.com/l-smash/l-smash Install LSMASHSource VapourSynth plugin from https://github.com/AkarinVS/L-SMASH-Works
See http://www.vapoursynth.com/doc/installation.html#windows-installation
Then download the latest release-x86_64-cachedir-cwd.zip from https://github.com/AkarinVS/L-SMASH-Works/releases/tag/vA.3j