[xconverge]

Looks to be managed here https://github.com/obsproject/obs-studio/tree/master/plugins

Pretty clean source tree to reference :) Seems to be unique per OS and not dependent on third party projects.

[dodgepong]

Indeed, all capture functionality is split out into plugins and they are platform-specific. Platform builds are handled by CMake to only include relevant plugins: https://github.com/obsproject/obs-studio/blob/master/plugins...