Well after a more search i found a opensource ffmped code sample as well as library of ffmpeg with dll at codeplex website at
FFmpeg Wrapper. It has source code from where i comes to know that i have to put 4 files with my project to achieve inbuilt functionality. so i put everything available in ffmped source code in my project/bin/debug folder and compare everything with ffmpeg sample code. it work now... i just wondering if this library is updated or not... i will replace updated resource with current resource ant then it will bake me a batter project...