Name: SmoothVideo Project (often abbreviated as SVP)
Homepage: svp-team.com
Why should this be included?: SVP allows videos to be easily interpolated in real-time with astonishing results. It has many features, tweakable settings, and can even be used to save the interpolated videos by piping the raw stream to ffmpeg. The Linux version offers the same abilities as the "Pro" Windows version, which is a huge benefit. While mpv offers basic interpolation abilities, SVP allows insane configuration and the freedom to watch in any video player as well as being able to permanently convert videos to higher frame rates. No other software like SVP exists in the repos, excluding mpv. It is of note that SVP can be easily downloaded and installed on Solus, but is not provided in the official repos.
Is it Open Source?: No (no license specified, only binary is available)
How many users?: Hard to estimate, but anyone who watches anime or appreciates the "soap-opera effect" will certainly want to use it.
Link to Source: The official source is located here, but the maintainer of SVP in the AUR kindly hosts versioned ".tbz2s" at this link.
I hope this will be an easy adoption as all dependencies, including optional, are in Solus's repos already! Clover should be enabled when building Mesa, however, for radeon/amdgpu driver users to take advantage of GPU-based decoding/SVP math/shaders. CUDA works out-of-the-box.