ffmpeg extract elementary streams from mp4

Question

I have successfully ported ffmpeg library to Android by using Bambuser's ffmpeg port. I'm currently investigating the ffmpeg's source codes especially ffplay.c and api-examples.c files.

I want to extract elementary streams from Android 2.2 recorded videos. For example I can record a H.263 encoded video in the MPEG-4 container. Lets say; test.mp4 file.

What I want to achieve is, I want to extract H.263 elementary stream video from the test.mp4 file something like test.h263.

It can be extracted by using the CLI of the ffmpeg. Just like;

ffmpeg -i test.mp4 -vcodec copy test.h263

But unfortunately I don't know how to extract elementary stream from a container by using the API of ffmpeg.

Thanks.