Apparently you can access DirectShow through Interop (see
http://www.codeproject.com/cs/media/directshownet.asp
). This would be the fastest, performance wise.

Personally I'm still using VFW (Video for Windows) API's because they
are so simple and have been around forever. Plus the code has to able
to run on machines that I have no way of knowing in advance whether
DirectShow is even supported. But I haven't tried through C# yet. My
guess is you'd have to wrap each VFW api with DllImportAttribute.