From what I recall (it's been a few months since I researched this) Windows 8 and later support a much faster mode for screen capturing that Windows 7 doesn't support, so OBS doesn't support it.
(see "Desktop Duplication API" on MSDN. Basically, Microsoft intentionally didn't port that specific useful functionality to Windows 7 but did a myriad of other related DLLs/frameworks.)
https://msdn.microsoft.com/en-us/library/windows/desktop/hh404487(v=vs.85).aspx
https://msdn.microsoft.com/en-us/library/windows/desktop/jj863687(v=vs.85).aspx
1 - How does OBS detect this support in the code?
2 - Would people be interested in a fork that enabled it for Windows 7?
3 - (Related to #1) What functions / source files would be a good place to start looking?
There was work on enabling DXGI (which Desktop Duplication uses) on Windows 7 through some hacked DLL's, etc.
https://github.com/rgcjonas/dd4seven
The project is completely unsupported/no warranty but I think it's worth a shot. Every time I touch my Windows 10 machines Microsoft finds a new way to screw me over (Constant 100% disk usage, yay!) so I keep putting off Windows 7 for my main machine. Hence, my interest in this capture mode.
(see "Desktop Duplication API" on MSDN. Basically, Microsoft intentionally didn't port that specific useful functionality to Windows 7 but did a myriad of other related DLLs/frameworks.)
https://msdn.microsoft.com/en-us/library/windows/desktop/hh404487(v=vs.85).aspx
https://msdn.microsoft.com/en-us/library/windows/desktop/jj863687(v=vs.85).aspx
1 - How does OBS detect this support in the code?
2 - Would people be interested in a fork that enabled it for Windows 7?
3 - (Related to #1) What functions / source files would be a good place to start looking?
There was work on enabling DXGI (which Desktop Duplication uses) on Windows 7 through some hacked DLL's, etc.
https://github.com/rgcjonas/dd4seven
The project is completely unsupported/no warranty but I think it's worth a shot. Every time I touch my Windows 10 machines Microsoft finds a new way to screw me over (Constant 100% disk usage, yay!) so I keep putting off Windows 7 for my main machine. Hence, my interest in this capture mode.