可以试一试open source的Wrapper:
Solid FFmpeg C# .Net Wrapper
http://www.ffmpeg-csharp.com/
Solid FFmpeg C# .Net Wrapper is designed for developers who use ffmpeg in C# / .Net projects. It wrappers ffmpeg library to ActiveX COM component. Just reference the this component in your C# projects and enjoy the powerful funciontalities of FFmpeg. Tested compatible with C#, VB.Net, ASP.Net, VB6, ASP, VC++, MFC.