Android FFMPEG example to get frames from video using NDK

I want to develop video merge application in android. I just able to generate ffmpeg.so file using NDK and JNI. But now I want to get frames of input video(around 15 sec.). Any one have an idea how to get the frames from video using ffmpeg? Is there direct native method available for that to get frames in ffmpeg? And how to pass command from java class to native mathod to perform video merging functionality? Just give me solution for that.