Need help: extract from code the process of converting 3gp-->jpeg

hey everyone,

i'm developing a mobile app which is needed to be as small as possible.

i'm using ffmpeg to get the first frame of a 3gp video (like a video thumbnail).

so to cut down the application size, i thought about getting only the relevant part of the code to convert 3gp to 1st frame jpeg.

the problem is that i don't know c++ too well and can't do this on my own.

is anyone willing to help me?