qcap.dll is part of DirectShow

There. I saved you 10 minutes of searching through hijacked Google results.

Missing? Re-install DirectX
Designed not to run?  Check to see if you’re cross referencing the 64-bit dll with a 32 bit DirectX applicaction.
Need the 32 bit version? Install DirectX 9.0c

Source: https://msdn.microsoft.com/en-us/library/windows/desktop/dd377592%28v=vs.85%29.aspx